RIPK1/RIPK3 promotes vascular permeability to allow tumor cell extravasation independent of its necroptotic function

OPEN RIPK1/RIPK3 p omo es ascula pe meabili y o allow umo cell ex a asa ion independen o i s nec op o ic unc ion Kay Hänggi 1 , Laza os Vasilikos 1 , Aida F ei e Valls 2,3 , Rosa io Ye bes 2 , Janin Knop 1 , Lisanne M Spilgies 1 , K is y Rieck 1 , T isha Mis a 1 , John Be in 4 , Pe e J Gough 4 , Thomas Schmid 3 , Ca men Ruiz de Almodò a 2 and W Wei-Lynn Wong* ,1 Nec op osis is an in lamma o y o m o p og ammed cell dea h equi ing ecep o -in e ac ing p o ein kinase 1, 3 (RIPK1, RIPK3) and mixed lineage kinase domain-like p o ein (MLKL). The kinase o RIPK3 phospho yla es MLKL causing MLKL o o m a po e-like s uc u e, allowing in acellula con en s o elease and cell dea h o occu . Al e na i ely, RIPK1 and RIPK3 ha e been shown o egula e cy okine p oduc ion di ec ly in luencing in lamma o y immune in il a es. Recen da a sugges ha nec op osis may con ibu e o he malignan ans o ma ion o umo cells in i o and we asked whe he nec op osis may ha e a ole in he umo mic oen i onmen al e ing he abili y o he umo o g ow o me as asize. To de e mine i nec op osis in he umo mic oen i onmen could p omo e in lamma ion alone o by ini ia ing nec op osis and he eby in luencing g ow h o me as asis o umo s, we u ilized a syngeneic umo model o me as asis. Loss o RIPK3 in he umo mic oen i onmen educed he numbe o umo nodules in he lung by 46%. Loss o he kinase ac i i y in RIPK1, a membe o he nec osome also educed umo nodules in he lung by 38%. Howe e , he loss o kinase ac i i y in RIPK3 o he loss o MLKL only ma ginally al e ed he abili y o umo cells o o m in he lung. Using bone ma ow chime as, he dec ease in umo nodules in he Ripk3 −/− appea ed o be due o he s omal compa men a he han he hema opoie ic compa men . T ansmig a ion assays showed dec eased abili y o umo cells o ansmig a e h ough he ascula endo helial laye , which co ela ed wi h dec eased pe meabili y in he Ripk3 −/− mice a e umo injec ion. In esponse o pe meabili y ac o s, such as ascula endo helial g ow h ac o , RIPK3 null endo helial cells showed dec eased p38/HSP27 ac i a ion. Taken oge he , ou esul s sugges an al e na i e unc ion o RIPK1/RIPK3 in ascula pe meabili y leading o dec eased numbe o me as asis. Cell Dea h and Disease (2017) 8, e2588; doi:10.1038/cddis.2017.20; published online 2 Feb ua y 2017 Cell dea h is conside ed o be one o he hallma ks o malignancy –ei he by up egula ion o an i-apop o ic genes o down egula ion o silencing o p o-apop o ic genes. 1 Nec op- osis is a p og ammed cell dea h pa hway igge ed by umo nec osis ac o (TNF), Fas, Toll-like ecep o ligands and ype I in e e on upon loss o inhibi ion o caspase-8. 2–6 Unde - s anding whe he nec op osis is pa o he cell dea h hallma k o malignancy has become an a ea o in ense esea ch. Recep o -in e ac ing p o ein kinase 1 (RIPK1), a mul i- unc ional p o ein ha con ains an N- e minal Se /Th kinase domain, is known o be a c i ical egula o a he decision poin o cy okine induced NF-kB ac i a ion o su i al o cell dea h by ei he apop osis o nec op osis. 7 Nec op osis is igge ed by RIPK1 in e ac ion wi h RIPK3, RIPK3 dime iza ion, au ophospho yla ion o RIPK3 and subsequen phospho yla- ion o mixed lineage kinase domain-like p o ein (MLKL). 8–10 Upon phospho yla ion, MLKL is belie ed o o m a po e complex ha can comp omise cell memb ane in eg i y 11,12 esul ing in he elease in acellula con en s. The esul is an in lamma o y esponse o he elease o dange -associa ed molecula pa e ns and/o he di ec egula ion o cy okines by RIPK1/RIPK3 dime iza ion. 13 Recen e idence sugges s RIPK3 is a umo supp esso . RIPK3 has been ound o be epigene ically silenced in b eas and panc ea ic cance issue 14,15 and in melanoma cell line. 16 In umo models, loss o RIPK3 aided a TAK1-induced in lamma ion model o hepa oca cinogenesis, 17 whe eas loss o RIPK3 in combina ion wi h in e nal andem duplica ion mu a ions o FMS-like y osine kinase-3 led o an inc ease in leukemia in i o, which was because o he absence o in lammasome ac i a ion. 18 Exp ession o RIPK3 in pa ien samples also has been associa ed wi h disease ou come. In ce ical cance s, low RIPK3 p o ein exp ession in pa ien biopsies co ela ed o a educed esponse o PolyIC-based adju an immuno he apeu ic app oaches. 19 In pa ien s su e - ing om in es inal bowel disease and p esen ing wi h colo - ec al cance , loss o RIPK3 exp ession was de ec ed in neoplas ic issue compa ed wi h non-neoplas ic and he loss o exp ession was co ela i e o a poo p ognosis. 20 These indings sugges a ole o RIPK3 and po en ially nec op osis in umo igenesis, as well as p ognosis. By con as , he dele ion o RIPK1, RIPK3 o MLKL in b eas cance cell lines educed he umo igenic po en ial o he cell o o m colonies and subcu aneous umo s in 1 Ins i u e o Expe imen al Immunology, Uni e si y o Zu ich, Zu ich, Swi ze land; 2 Biochemis y Cen e , Heidelbe g Uni e si y, Heidelbe g, Ge many; 3 Depa men o Gene al, Visce al and T ansplan a ion Su ge y, Heidelbe g Uni e si y, Heidelbe g, Ge many and 4 Pa e n Recogni ion Recep o Disco e y Pe o mance Uni , Immuno- In lamma ion The apeu ic A ea, GlaxoSmi hKline, College ille, PA, USA *Co esponding au ho : WW-L Wong, Ins i u e o Expe imen al Immunology, Uni e si y o Zu ich, Win e hu e s asse 190 Y44 J55, Zu ich 8057, Swi ze land. Tel: +41 44 635 3720; Fax: +41 44 635 6883; E-mail: [email protected] Recei ed 12.10.16; e ised 22.12.16; accep ed 03.1.17; Edi ed by J Zhang Ci a ion: Cell Dea h and Disease (2017) 8, e2588; doi:10.1038/cddis.2017.20 O ficial jou nal o he Cell Dea h Di e en ia ion Associa ion www.na u e.com/cddis immunocomp omised mice. 21 To add o he complexi y, inc eased exp ession in RIPK3, RIPK1 and MLKL was ound in pa ien panc ea ic duc al adenoca cinoma (PDA) compa ed wi h no mal issue and he loss o RIPK3 in a V12K-Ras- induced PDA model inc eased su i al by educing he exp ession o CXCL-1/Mincle pa hway and by al e ing he p esence o umo -supp essi e immune cell. 22 In addi ion, ou wo k and o he s show ha RIPK1/RIPK3 d i e cy okine p oduc ion ei he in conjunc ion wi h ini ia ing nec op osis o comple ely independen ly. 23,24 This makes i di icul o in e p e in lamma ion d i en in i o models o umo igenesis in RIPK3-de icien mice. We sough o di e en ia e he ole o RIPK3 o nec op osis in umo igenesis e sus he umo mic oen i onmen by u ilizing syngeneic mouse umo models. These models can be used o simula e me as asis, wha 90% o cance pa ien s die om a he han he p ima y umo . Simila o ecen ly published esul s, we ound he ole o RIPK3 in he umo mic oen i on- men was no because o he al e ed immune esponse bu he abili y o umo cells o ex a asa e in o he lung. 25 Howe e , we ound he kinase ac i i y o RIPK1 bu no RIPK3 kinase ac i i y was impo an in he ex a asa ion s ep o me as asis. Loss o MLKL showed a educ ion bu no signi ican numbe o umo nodules o med in he lung compa ed wi h Ripk3 −/− . Ou da a shows ha in addi ion o he possibili y o ac i a ing nec op osis h ough a dea h ecep o 6-media ed manne as p e iously ound, RIPK3 has a c i ical ole as signaling pla o m downs eam o s imuli p omo ing pe meabili y h ough p38/ HSP27. These da a suppo he ole o RIPK1/RIPK3 as a signaling pla o m in p omo ing ascula pe meabili y equi ed o umo cell ex a asa ion. Resul s Loss o RIPK3 esul s in dec eased umo nodules in he lung. To de e mine whe he umo cells we e able o o m a solid umo , Ripk3 −/− mice we e injec ed subcu aneously wi h B16-F10 cells. In ag eemen wi h ecen ly published da a, 22 solid umo s o med a he same a e and olume in bo h wild- ype and Ripk3 −/− mice (Figu e 1a). This sugges ed he loss o RIPK3 in he umo mic oen i onmen did no a ec es ablished umo cells om g owing. To de e mine i RIPK3 in he umo mic oen i onmen could ha e a ole in a umo me as asis model, B16-F10 umo cells we e injec ed ail ein in o wild- ype mice. Lung homogena es we e made 2, 6 and 12 h a e ail ein injec ion and RIPK3 le els we e assayed 0 50 100 150 200 250 Numbe o umo nodules ** Ripk3-/- W 0 10 20 30 Numbe o umo nodules 40 Ripk3-/- W W Ripk3-/- 50 100 Pe cen age 0 75 25 Ripk3-/- W La ge Medium Small Tumo olume (mm3) 200 300 400 500 100 0 02 141210864 days pos injec ion o B16-F10 Numbe o umo nodules Ripk3 0 50 10 150 200 +/+ +/- -/- * RIPK3 β-Ac in 53 RIPK1 68 41 123456789 PBS 6h 12h B16-F10 Mouse MLKL 53 B16-F10 (h) Change o RIPK3 p o ein exp ession 012 1.0 2.0 3.0 0 * ** 6 kDa W Ripk3-/- * Figu e 1 Loss o RIPK3 in he umo mic oen i onmen educes umo nodules in he lung in a umo model o ex a asa ion. (a)Wild- ype (W ) and Ripk3 −/− mice we e injec ed subcu aneously wi h 1 × 10 5 B16-F10 umo cells and umo size was measu ed o e ime (pooled da a o n=2 expe imen s; 5–7 mice used pe g oup in each expe imen ). (b) RIPK3 bu no RIPK1 o MLKL p o ein le els we e ele a ed in o al lung lysa es o wild- ype mice 6 and 12 h a e injec ion o B16-F10 cells shown by ep esen a i e immunoblo and co esponding quan i ica ion o pixel densi y om h ee mice pe imepoin . Fold change ela i e o un ea ed W con ol is shown om alues no malized o ac in (s a is ical analysis by one-way ANOVA). (c) Tumo nodules we e coun ed 14 days pos ail ein injec ion (dpi) o B16-F10 cells (2 × 10 5 ) in o Ripk3 li e ma e con ol mice (le panel, n=1; 3–4 mice used pe g oup) and umo nodules we e coun ed 14 dpi o B16-F10 cells (2 × 10 5 ) in o W and Ripk3 −/− mice ( igh panel, pooled da a shown o n=3 expe imen s; 3–5 mice used pe g oup in each expe imen ). (d) Co esponding size is shown o umo nodules classi ied mac oscopically in o la ge (41 mm), medium (0.5 mm–1 mm) and small (o0.5 mm) shown (pooled, n=3), and co esponding ep esen a i e mac oscopic pic u es o he lungs we e shown. (e) Tumo nodules we e coun ed 20 dpi o MC-38 cells (3 × 10 5 ) in o W and Ripk3 −/− mice (n=1; 6 mice used pe g oup; P=0.14). Each do ep esen s a mouse excep s a ed o he wise; s a is ical analysis by - es excep s a ed o he wise. *Po0.05, **Po0.01 RIPK1/RIPK3 p omo es ascula pe meabili y K Hänggi e al 2 Cell Dea h and Disease by immunoblo ing. A e 12 h, he le el o RIPK3 p o ein was app oxima ely wo old highe (Figu e 1b), sugges ing a po en ial ole o RIPK3 in umo o ma ion in he lung. In e es ingly, no changes in RIPK1 o MLKL le els we e seen (Figu e 1b). Using li e ma es, mice we e injec ed ail ein wi h B16-F10 cells and 14 days pos injec ion (dpi) lungs we e coun ed o umo nodules. The numbe o umo nodules we e educed signi ican ly by app oxima ely 50% (Figu es 1c; Po0.05). In e es ingly, Ripk3 +/− mice showed an in e media e pheno ype be ween wild- ype and Ripk3 −/− . Addi ional wild- ype and Ripk3 −/− mice we e hen injec ed ail ein wi h B16-F10 cells and 14 dpi, a e blinding, he lungs we e coun ed o umo nodules. The e was a 46% (±7.6%) dec ease in umo nodules in he RIPK3 null lungs compa ed wi h wild- ype (Figu es 1d; Po0.01). The size o he umo nodules was ca ego ized in o la ge, medium o small based on wid h o he nodule om pic u es o he lungs and al hough no signi ican , he e was a endency owa d smalle nodules in Ripk3 −/− mice (Figu e 1e). To ensu e he pheno ype was no es ic ed o B16-F10 umo model, MC-38 colon ca cinoma cells we e injec ed in a enously and umo nodules in he lung we e coun ed 20 dpi. Consis en wi h he B16-F10 umo model, a dec eased numbe o nodules in he Ripk3 −/− mice we e ound compa ed wi h wild- ype mice (Figu es 1d; P=0.14) sugges ing he dec ease in umo nodules in he Ripk3 −/− was no dependen on he umo cell ype. Loss o RIPK1 kinase ac i i y bu no RIPK3 kinase ac i i y educe umo nodule load in he lung. The nec osome is composed o RIPK1 and RIPK3 and he kinase ac i i y o RIPK1 and RIPK3 is belie ed o be impo an and/o essen ial o ac i a ing nec op osis by phospho yla ing MLKL. Cu en ly, MLKL is conside ed o be he essen ial and he only W Ripk3K51A/K51A 200 100 0 150 50 Numbe o umo nodules W K45A/K45A W /K51A Ripk3 Numbe o umo nodules 600 200 0 400 K51A/K51A 0h W Ripk3-/- Lung: DAPI/TUNEL 6h 12h Posi i e C l. B16-F10 (hou s) W Numbe o umo nodules W Ripk3 -/- Mlkl -/- Mlkl-/- Ripk3-/- 0 100 200 300 400 500 ** * ** 300 100 0 200 Numbe o umo nodules Ripk1K45A/K45A W Ripk1 Figu e 2 RIPK1 kinase ac i i y bu no RIPK3 kinase ac i i y o MLKL in he umo mic oen i onmen is needed o umo nodule o ma ion in he lung. Tumo nodules we e coun ed 14 dpi o B16-F10 cells in o (a)W and Ripk1 K45A/K45A mice (pooled da a o n=2 expe imen s; 4–7 mice we e used pe g oup in each expe imen ) and ep esen a i e pic u es o lungs a e shown, (b)W and Ripk3 K51A/K51A mice (pooled da a o n=2 expe imen s; 5–8 mice we e used pe g oup in each expe imen ) and (c) in o Ripk3 W /K51A and Ripk3 K51A/K51A mice (pooled da a o n=4 expe imen s; 3–4 mice we e used pe g oup in each expe imen ). (d) Tumo nodules we e coun ed 14 dpi o B16-F10 cells in o W , Mlkl −/− and Ripk3 −/− mice and ep esen a i e pic u es a e shown (da a om o n=2 expe imen s; 2–6 mice we e used pe g oup in each expe imen ). (e) Pa a in-embedded lung sec ions om mice injec ed ail ein wi h B16-F10 a indica ed imepoin s we e s ained o TUNEL (FITC) and DAPI. In es ine o ciap1 −/− mice injec ed wi h TNF was used as a posi i e con ol and ed a ows indica e TUNEL-posi i e cells. Each do ep esen s a mouse; s a is ical analysis by - es ; all scale ba s, 50 μm. **Po0.01 RIPK1/RIPK3 p omo es ascula pe meabili y K Hänggi e al 3 Cell Dea h and Disease known e ec o p o ein o nec op osis. 10,11 To de e mine i p o eins composing he nec osome we e impo an in he educ ion o umo nodules in he lung, RIPK1 kinase dead (K45A) mice we e injec ed wi h B16-F10 cells ( ail i. .) and a e 14 dpi, he lungs we e ha es ed, blinded and umo nodules we e coun ed. Tumo nodules in he Ripk1 K45A/K45A mice we e dec eased by 38.3% (±8.5%) compa ed o wild- ype mice (Figu es 2a; Po0.05). Nex , RIPK3 kinase dead (K51A) mice we e injec ed ail ein wi h B16-F10 cells and again, a e 14 dpi, lungs we e blinded and nodules we e coun ed in he lung. No di e ence in he numbe o umo nodules we e ound (Figu e 2b). As p o ein le els o he kinase dead RIPK3 K51A mu an ha e been shown o be dec eased because o p o ein ins abili y, we assessed he le els o p o ein p esen in lung homogena es and ound he exp ession o he RIPK3 mu an o be signi ican ly dec eased (Supplemen a y Figu e 1a). 26 To con ol o he dec eased change in exp ession, we compa ed he Ripk3 w /K51A wi h he Ripk3 K51A/K51A mice. No di e ence in he numbe o umo nodules we e o med in he lung (Figu e 2c). To e i y ha loss o RIPK3 kinase ac i i y was able o block nec op osis, isola ed endo helial cells (ECs) om he lungs o Ripk3 K51A/K51A mice we e es ed wi h ypical ac i a o s o nec op osis, TNF, zVAD and/o Smac mime ics (Supplemen a y Figu e 1b). As expec ed, compa ed wi h wild- ype he RIPK3-de icien and Ripk3 K51A/K51A -exp essing cells we e esis an o nec op osis caused by he combina ion o TNF, zVAD and Smac mime ic ea men . In e es ingly, al hough he kinase ac i i y o RIPK1 was equi ed, i appea ed he loss o kinase ac i i y om RIPK3 was no equi ed in umo o ma ion in he lung. Finally, o assess i nec op osis was indeed he eason o he dec ease in umo nodules in he lung, we injec ed B16-F10 cells ail ein in o wild- ype, Mlkl −/− and Ripk3 −/− mice. Only a sligh dec ease in he numbe o umo nodules was seen in Mlkl −/− mice, whe eas he educ ion o umo nodules was seen again in Ripk3 −/− mice (Figu e 2d). The combined esul s om he kinase dead RIPK3 and MLKL-de icien mice sugges ed an al e na i e ole o RIPK3 in ol ing he kinase ac i i y o RIPK1. As he loss o RIPK3 in Vucu e al. 17 led o an inc ease in caspase-8-dependen apop osis in a TAK1 in lamma o y- d i en hepa oca cinoma, we assessed o he p esence o cell dea h in he lung a e B16-F10 cells we e injec ed in he mice. TUNEL s aining was used o de e mine cell dea h, as his echnique will pick up bo h apop osis o nec osis/ nec op osis. 27 Fo his, lung sec ions o mice injec ed wi h B16-F10 a di e en imepoin s (0, 6 and 12 h) we e analyzed o TUNEL-posi i e cells. The posi i e con ol in es inal 150 100 50 0 CD45.1 BM ecipien Numbe o umo nodules To al lux [p/s] (x104) Time a e B16-F10 luc (h) 61224 0 10 15 W Ripk3-/- W Ripk3-/- B16-F10 (h) 06240624 0 0.6 0.4 0.2 0.8 1 Neu ophils To al cell coun pe g lung (x107) To al cell coun pe g lung (x107) B16-F10 (h) 0.25 0 0.50 0.75 1 06240624 In lamma o y Monocy es [pg/ml] 0 200 400 600 800 CCL-2/MCP-1 B16-F10 (h) 06240624 [pg/ml] 0 100 200 300 400 CXCL-1/G o-α B16-F10 (h) 06240624 W Ripk3-/- CD45.2 BM ecipien Ripk3 -/- Ripk3-/- BM dono CD45.1 BM dono Numbe o umo nodules 0 100 200 300 5 0 15 20 10 06240 6 24 B16-F10 (h) [pg/ml] IL-1β *** *** *** *** *** *** Figu e 3 Loss o RIPK3 in he mic oen i onmen does no al e ea ly immune and cy okine esponse upon B16-F10 injec ion and bone ma ow econs i u ion shows he s omal compa men o be esponsible. (a) B16-F10 luci e ase cells home o he lung in bo h W and Ripk3 −/− mice measu ed by IVIS luminescen imaging ( ep esen a i e shown, 4–5 mice pe g oup, n=2). (b) Cy okine le els in o al lung lysa es we e measu ed by mul iplex bead assay and le els o CCL-2, CXCL-1, IL-1βand TWEAK a e shown (n=2). (c) Co esponding immune cell in il a ion analysis by low cy ome y shows in lamma o y monocy es (SiglecF − Ly6G − Ly6C hi CCR2 + ) and neu ophil g anulocy e (SiglecF − CD11b + Ly6G + ) popula ions. Popula ions we e p e-ga ed on single s, li e cells, Te 119 − and CD45 + cells. (d) Tumo nodules we e coun ed 14 dpi o B16-F10 in o CD45.1 ecipien mice econs i u ed wi h CD45.2 W and CD45.2 Ripk3 −/− bone ma ow cells (n=3) and CD45.2 o Ripk3 −/− ecipien mice econs i u ed wi h CD45.1 o Ripk3 −/− bone ma ow cells (n=2). Each do ep esen s a mouse; s a is ical analysis done by one-way ANOVA and Bon e oni pos - es . ***Po0.001 RIPK1/RIPK3 p omo es ascula pe meabili y K Hänggi e al 4 Cell Dea h and Disease epi helial cells om wild- ype mice injec ed wi h TNF we e s ained posi i e o TUNEL, whe eas lungs om wild- ype o Ripk3 −/− mice did no s ain TUNEL posi i e (Figu e 2e). In addi ion, li le o no caspase-3 ac i i y was measu ed in lung homogena es o mice injec ed wi h B16-F10 a di e en imepoin s (Supplemen a y Figu e 1c). This sugges s he kinase ac i i y o RIPK3 and he e o e he abili y o nec op osis o occu in he umo mic oen i onmen did no al e umo nodule o ma ion. Tumo cells home o he lung in bo h wild- ype and Ripk3 −/− mice wi h simila immune cell in il a es. To de e mine he addi ional ole RIPK3 may ha e in me as asis, we nex assessed whe he he B16-F10 cells we e able o home o he lung in he Ripk3 −/− mice. B16-F10 luci e ase cells we e injec ed and moni o ed a e injec ion o mo e- men o he lung o e ime. Equi alen luminescence was measu ed be ween wild- ype and Ripk3 −/− mice wi hin he i s 24 h (Figu e 3a). This sugges ed he B16-F10 cells we e su i ing and homing o he lung he same in he Ripk3 −/− mice compa ed wi h wild- ype. Chemokines such as C-C mo i chemokine ligand 2 (CCL-2) ha e been shown o induce signaling o ec ui in lamma o y monocy es, as well as induce endo helial ex a asa ion. 28,29 To de e mine i RIPK3 was c i ical in p oducing p o- in lamma o y media o s o ec ui myeloid in il a es pos injec ion o B16-F10 cells, cy okines/chemokines we e ana- lyzed in lungs o wild- ype and Ripk3 −/− mice. We examined whe he chemokines/cy okines we e al e ed in Ripk3 −/− mice compa ed wi h wild- ype mice a e B16-F10 injec ion using lung homogena es. An inc ease in CCL-2, CXCL-1 and IL-1β was seen in bo h wild- ype and Ripk3 −/− mice (Figu e 3b). TNF was below he limi o de ec ion. This sugges s he abili y o p oduce cy okines o a ac monocy es was unc ional in he lung o Ripk3 −/− mice. We hen assessed he immune in il a es in he lung by low cy ome y. A e 6 h pos B16- F10 injec ion, a signi ican inc ease in he numbe o in lamma o y monocy es (Ly6C hi CCR2 + ) we e seen in Ripk3 −/− mice compa ed wi h wild- ype (Figu e 3c). Simila ly, CD11b + dend i ic cells inc eased, whe eas he CD103 + dend i ic cell popula ion dec eased in wild- ype and Ripk3 −/− lungs a e B16-F10 injec ion (Supplemen a y Figu e 2). Na u al kille T cells also esponded in a simila manne in bo h wild- ype and Ripk3 −/− lungs a e B16-F10 injec ion (Supplemen a y Figu e 2). Loss o RIPK3 in he s oma a ec s umo nodule o ma ion in he lung. To de e mine he po en ial o he hema opoie ic o s omal compa men o ha e a ole in he educ ion in umo nodules ound in Ripk3 −/− lungs, we pe o med bone ma ow chime ic expe imen s. CD45.1 ecipien mice we e i adia ed and econs i u ed wi h ei he wild- ype o RIPK3-de icien bone ma ow. Only mice wi h econs i u ion e iciency 495% we e used o B16-F10 injec ion (da a no shown). A e 14 dpi, umo nodules in he mice wi h RIPK3-de icien hema opoie ic compa men Pe cen age o EC popula ion Cell Dea h assay: Co-cul u e B16-F10/Endo helial cells (8h) Cell Dea h o EC Cell Dea h o B16-F10 0 25 50 75 100 Annexin V+ Li e-Dead+/Annexin V- Li e-Dead+/Annexin V+ W Ripk3 -/- Mlkl-/- nd. - B16-F10: TNF/SM: zVAD: - +++ ++ ++ -- --- - ++ - --- --- --- ++++++ +++ --- --- ------ To al B16-F10 cells ansmig a ed pe inse 0 50 100 150 200 +W +Ripk3 -/- Monocy es: - EC W EC Ripk3K51A/K51A Ripk3-/- EC Figu e 4 RIPK3 p omo es umo cell ansendo helial mig a ion independen o i s abili y o block nec op osis. (a) Boyden chambe ansendo helial mig a ion assay using B16-F10 cells and p ima y CD31 + ECs isola ed om lungs o W ,Ripk3 −/− o Ripk3 K51A/K51A mice. P ima y monocy es we e isola ed on he day o seeding B16-F10 cells and 20 h la e , answells we e ixed, s ained and imaged. Image analysis was blinded and umo cells we e coun ed pe ield o iew. The da a a e pooled om n=2 expe imen s; 1–3 answell inse s we e assayed pe g oup in each expe imen and 10–17 ields pe iew we e analyzed pe answell inse . To al numbe o B16-F10 ansmig a ed cells pe answell inse is shown. Each do ep esen s an inse . S a is ical analysis by one-way ANOVA and Bon e oni pos - es . (b) EC monolaye s om W ,Ripk3 −/− and Mlkl −/− mice we e co-incuba ed wi h PKH26 + B16-F10 (+ =3×10 4 ;++=9×10 4 ) cells and assayed o cell dea h 8 h la e by low cy ome y (n=3; nd =no de e mined). Cells we e s ained o annexin Vand PI (li e/dead) o iden i y ea ly apop o ic cells (Li e/Dead − annexin V + ) and dead cells (annexin V + Li e/Dead + annexin V + o Li e/Dead + annexin V − ). S a is ical analysis done by one-way ANOVA and Bon e oni pos - es RIPK1/RIPK3 p omo es ascula pe meabili y K Hänggi e al 5 Cell Dea h and Disease we e simila in numbe compa ed wi h mice wi h wild- ype hema opoie ic compa men (Figu e 3d, le panel). This sugges s ha he hema opoie ic compa men does no in luence he o al numbe o umo nodules in he lung. We hen i adia ed Ripk3 −/− and CD45.2 mice and econs i u ed he bone ma ow wi h wild- ype o RIPK3-de icien bone ma ow. A e 14 dpi, umo nodules we e coun ed. In compa ison wi h wild- ype mice econs i u ed wi h Ripk3 −/− bone ma ow, he e was a dec easing amoun o umo nodules in he Ripk3 −/− mice econs i u ed wi h wild- ype (17.6% ±23) o Ripk3 −/− bone ma ow (38.6% ±22.6), espec i ely (Figu e 3d, igh panel). Taken oge he , he da a sugges ed ha he educ ion in umo nodules in he Ripk3 −/− mice was because o he s omal compa men and no because o he hema opoie ic compa men . RIPK3 p omo es umo cell ex a asa ion independen o i s kinase ac i i y. To o m umo s in he lung, he umo cells mus ex a asa e pas he ascula endo helial ba ie . To de e mine i he e was a umo cell ansmig a ion de ec , B16-F10 E ans blue pe lung [ug/ml] -+-+ 0 5 10 15 20 W Ripk3-/- FGF-basic 0 6 24 0 6 24 B16-F10 (h) 0.5 0 1.0 2.0 1.5 [ng/ml] 20 0 60 80 40 [pg/ml] B16-F10 (h) TWEAK ** *** ** 06240 6 24 0 6 24 0 6 24 B16-F10 (h) 2 0 6 4 [ng/ml] MMP-9 *** ** ** W Ripk3-/- 0.5 0 1.5 2.5 2.0 1.0 [ng/ml] 06240 VEGF-A 6 24 B16-F10 (h) VEGF-A 164 To al B16-F10 cells ansmig a ed pe inse 100 200 300 -+-+ VEGF-A164 ++ Fold change (RFU) o dex an-FITC 0 0.50 1.00 1.50 W Ripk3-/- -- ** 0.25 1.25 0.75 W Ripk3-/- siC l siRipk1 VEGF-A 164 -+-+ Sp ou leng h (Fold change) 0 1.0 2.0 1.5 2.5 0.5 siC l siRipk3 ** ns ** * +VEGF-A mock siC l siRipk3 +VEGF-A mock siC l siRipk1 0 0.5 1.5 1.0 2.5 2.0 0 0.5 1.5 1.0 2.0 Sp ou leng h (Fold change) DMSO Nec-1 VEGF-A 164 -+-+ *** -+-+ VEGF-A 164 Figu e 5 RIPK1 kinase ac i i y and RIPK3 p omo es VEGF-A-dependen ascula pe meabili y and sp ou ing. (a) Le els o angiogenic- and emodeling ac o s in o al lung lysa es we e measu ed by mul iplex bead assay and le els o VEGF-A, FGF-basic, TWEAK and MMP-9 a e shown (da a pooled o n=2 expe imen ; S.E.M.; 4–6 mice we e used pe g oup; each do ep esen s a mouse). (b) E ans blue blood essel pe meabili y assay o W and Ripk3 −/− lungs 20 h a e B16-F10 umo cell injec ion i. . (pooled da a o n=2 expe imen s, 4–5 mice we e used pe g oup in each expe imen ; each do ep esen s a mouse). (c) P ima y lung endo helial monolaye on answell inse s we e ea ed wi h VEGF-A 164 (100 ng/ml) o 4 h and dex an-FITC pe meabili y assay was pe o med. Da a show ela i e luo escence uni (RFU) o dex an-FITC ha passed EC ba ie no malized o un ea ed wild- ype (pooled da a o n=5 expe imen s; S.E.M.; 2–3 answell inse s we e used pe g oup in each expe imen ; each do ep esen s a answell inse ). (d) Subsequen B16-F10 ansendo helial mig a ion assay was pe o med a e dex an-FITC pe meabili y assay and 20 h a e B16-F10 (PKH26 + ) cells we e seeded in o inse s, answells we e ixed, s ained and imaged. Image analysis was blinded and umo cells we e coun ed pe ield o iew. The da a a e pooled om n=2 expe imen s; 2–3 answell inse s we e assayed pe g oup in each expe imen and 10–17 ields pe iew we e analyzed pe answell inse . S.E.M. and o al numbe o B16-F10 ansmig a ed cells pe answell inse is shown. Each do ep esen s an inse . S a is ical analysis by one-way ANOVA and Bon e oni pos - es . (e) HUVECs we e ans ec ed wi h siRNAs a ge ing RIPK3 o ( ) RIPK1 (le panel) o ea men wi h nec os a in-1 (Nec-1, igh panel) and sp ou ing assay was pe o med. Rep esen a i e luo escnece mic oscopy images a e shown. Da a om n=3 expe imen s; S.E.M.; s a is ical analysis by - es ; all scale ba s, 100 μm. *Po0.05, **Po0.01, ***Po0.001 RIPK1/RIPK3 p omo es ascula pe meabili y K Hänggi e al 6 Cell Dea h and Disease we isola ed CD31 + cells om he lungs o wild- ype, Ripk3 −/− o Ripk3 K51A/K51A mice and pe o med ansmig a ion assays. A dec eased numbe o B16-F10 cells ansmig a ed h ough Ripk3 −/− ECs compa ed wi h wild- ype o Ripk3 K51A/K51A ECs (Figu e 4a). We also de e mined i wild- ype monocy es could acili a e inc eased umo cell ansmig a ion. Two old mo e B16-F10 cells ansmig a ed h ough wild- ype endo helial monolaye in he p esence o monocy es (Figu e 4a). S ikingly, nei he he addi ion o wild- ype no Ripk3 −/− monocy es inc eased he abili y o B16-F10 cells o ansmi- g a e h ough a Ripk3 −/− endo helial monolaye . By con as , he addi ion o Ripk3 −/− monocy es did enhance B16-F10 ansmig a ion h ough wild- ype endo helial monolaye . Mo eo e , he Ripk3 K51A/K51A ECs allowed B16-F10 cells o ansmig a e h ough simila o wild- ype wi h ei he wild- ype o Ripk3 −/− monocy es. These esul s suppo he idea ha he hema opoie ic compa men does no ha e a ole in he loss o umo o ma ion in he Ripk3 −/− mice simila o indings in Figu e 3d and u he suppo s obse a ion ha he kinase ac i i y o RIPK3 in he ECs is no equi ed o he abili y o umo cells ansmig a e and umo nodules o o m in he lung (Figu es 2b and c). Cell dea h in p ima y ECs upon co-incuba ion o umo cells is independen o RIPK3 o MLKL loss. To de e mine i nec op osis occu ed o allow o ansmig a ion, we isola ed CD31 + cells om he lungs o wild- ype, Ripk3 −/− and Mlkl −/− mice. P ima y lung EC monolaye s we e incuba ed wi h ei he 3 × 10 4 o 9 × 10 4 B16-F10 cells. Cell dea h was assessed 8 h la e by low cy ome y as ou in i o imaging sugges ed he umo cells homed o he lung wi hin 6 h (Figu e 4b). B16-F10 cells we e s ained o iden i ica ion wi h he memb ane dye PKH26 and we e emo ed om he popula ion o cell dea h assessmen o ECs. Cells we e hen s ained using Annexin V FITC and p opidium iodide (PI) o disc imina e li e, ea ly apop o ic, o la e apop o ic o nec o ic cells. The o e all pe cen age o dead wild- ype ECs (ei he ea ly apop o ic o la e apop o ic/nec o ic cells) inc eased by 1–3% wi h he inc easing amoun o umo cells, whe eas Ripk3 −/− o Mlkl −/− ECs only showed an inc ease in 1–2% dead cells upon 9 × 10 4 umo cell addi ion. Howe e , he pe cen age o la e apop o ic o nec o ic ECs inc eased upon umo cell addi ion was independen o he geno ype o he ECs. This sugges ed RIPK3 may ha e an addi ional ole o ha o he p oposed umo cell induced nec op osis as p oposed. 25 Loss o RIPK1 kinase ac i i y o comple e loss o RIPK3 al e s pe meabili y and essel sp ou ing in esponse o VEGF-A. Vascula pe meabili y has been p oposed as a model o umo me as asis whe e ascula endo helial g ow h ac o (VEGF), ib oblas g ow h ac o (FGF) o CCL-2 may in luence pe meabili y. 30–32 Recen da a show ha ac i a ion o VEGF leads o c-S c ac i a ion and change in VE-cadhe in dis ibu ion allowing o inc eased ascula pe meabili y and subsequen umo me as asis. 33 To de e - mine i ac o s in ol ed in ascula pe meabili y was a ec ed, we assayed o VEGF-A, FGF-b o TWEAK in lung homo- gena es o wild- ype and Ripk3 −/− mice injec ed wi h B16-F10 cells. In e es ingly, he loss o RIPK3 showed no inc ease in VEGF-A a 6 h a e B16-F10 cell injec ion compa ed wi h wild- ype (Figu e 5a). A dec ease in me allop o einase 9 (MMP-9) was de ec ed a 24 h a e B16-F10 cell injec ion in he lungs o Ripk3 −/− compa ed wi h wild- ype (Figu e 5a). VEGF-A and FGF-b was also de ec ed in supe na an o ansmig a ion assays o ei he wild- ype o Ripk3 −/− ECs wi h monocy es and umo cells a e 20 h. MMP-9 was dec eased in he supe na an o ansmig a ion assays o Ripk3 −/− ECs compa ed wi h wild- ype (Supplemen a y Figu e 3a). These da a sugges ed ha ac o s in ol ed in ascula pe meabili y we e p esen wi h he excep ion o VEGF, which was educed a 6 h in he lung o Ripk3 −/− a e B16-F10 cell injec ion. We he e o e assessed i pulmona y ascula pe meabili y a e umo injec ion was a ec ed in he Ripk3 −/− mice using he E ans blue pe meabili y assay. E ans blue dye binds o albumin and up ake o he dye in o gans is a measu e o issue pe meabili y. E ans blue dye was injec ed in o wild- ype and Ripk3 −/− mice 20 h pos injec ion o B16-F10 cells. The amoun o E ans blue dye in wild- ype lung homogena e inc eased sligh ly when B16-F10 cells we e injec ed, bu no inc ease in E ans blue dye was obse ed in Ripk3 −/− mice (Figu e 5b). To u he assess he issue o ascula pe meabili y, we ea ed p ima y ECs o 4 h wi h VEGF-A 164 ( e e ed he ea e as VEGF-A) and assayed o endo helial leakiness using dex an-FITC. Al hough a signi ican inc ease in app oxi- ma ely 15% o dex an-FITC de ec ed a e ea ing wild- ype ECs wi h VEGF-A, he e was no inc ease in pe meabili y seen in ea ed Ripk3 −/− ECs (Figu e 5c). We assessed whe he he loss o RIPK1 kinase ac i i y al e ed endo helial ba ie pe meabili y in esponse VEGF-A and ound he loss o RIPK1 kinase ac i i y led o no inc ease in endo helial pe meabili y in esponse o VEGF-A (Supplemen a y Figu e 3b). We hen asked i p e-s imula ion wi h VEGF-A could inc ease he numbe o B16-F10 cells mig a ing h ough an EC ba ie . Al hough he numbe o B16-F10 cells inc eased by app oxima ely 25% o a wild- ype endo helial ba ie , no inc ease in B16-F10 umo cells was seen o a Ripk3 −/− endo helial ba ie (Figu e 5d). To de e mine i o he unc ional oles o VEGF-A we e also comp omised by he lack o RIPK1 o RIPK3, we assessed essel sp ou ing. In e es ingly, when RIPK3 was down egula ed in human umbilical ein ECs (HUVECs), hese cells showed a wo old inc ease in basal essel sp ou ing. Impo an ly, he addi ion o VEGF-A induced he ou g ow h o essel sp ou s in wild- ype HUVECs (siRNA con ol) bu no in HUVECs whe e RIPK3 was silenced by siRNA (Figu e 5e). Consis en wi h p e ious epo s, HUVECs did no exp ess RIPK3 p o ein a high le els and e en a sligh educ ion in RIPK3 le els led o a di e ence in VEGF-A esponse in essel sp ou ing (Supplemen a y Figu e 3c). We hen assessed he ole o RIPK1 in essel sp ou ing and simila ly ound ha he loss o RIPK1 by siRNA o loss o kinase ac i i y o RIPK1 by use o Nec-1 led o a dec ease in essel sp ou ing in esponse o VEGF-A compa ed wi h wild- ype HUVECs (Figu e 5 ). Taken oge he , hese esul s show ha RIPK1 o RIPK3-de icien ECs ail o espond o umo -induced ascula pe meabili y o VEGF-A-induced pe meabili y and angiogenesis, esul ing in a de ec in B16-F10 ansendo helial mig a ion. RIPK1/RIPK3 p omo es ascula pe meabili y K Hänggi e al 7 Cell Dea h and Disease Loss o RIPK1 kinase ac i i y and comple e loss o RIPK3 in ECs dampens p38/HSP27 signaling in esponse o pe meabili y ac o s. To de e mine he po en ial mechanism o how RIPK3 may a ec ascula pe meabili y, we examined downs eam signaling in esponse o VEGF-A, VEGF-B o FGF-b. In esponse o VEGF-A, VEGF-B o FGF-b, wild- ype ECs showed an inc ease in phospho-p38 ollowed by he downs eam phospho yla ion o HSP27 p o ein, whe eas phospho-ERK1/2 dec eased in signal (Figu e 6a and Supplemen a y Figu e 4a). The in e se s a us o phospho- p38 and phospho-ERK1/2 in esponse o VEGF-A has been p e iously shown in HUVECs whe e ac i a ion o p38 leads o dec eased le els o ERK1/2 ac i a ion. 34 By con as , RIPK3 null ECs s imula ed wi h ei he VEGF-A, VEGF-B o FGF-b esul ed in educed phospho-p38 ac i a ion compa ed wi h wild- ype. Mo e s ikingly, he downs eam phospho yla ed p o ein, HSP27, was u he educed (Figu e 6a and Supplemen a y Figu e 4a). Con e sely, phospho yla ed ERK1/2 in he Ripk3 −/− ECs was inc eased compa ed wi h wild- ype e lec ing he dampened p38 ac i a ion in he RIPK3 knockou s. In e es ingly, Ripk3 −/− ECs wi hou s imula ion, had an inc eased basal le el o phospho-p38 p esen compa ed wi h wild- ype cells. No majo di e ences in he ac i a ion o p38/HSP27 be ween wild- ype and Ripk3 −/− ECs was seen when ea ed wi h TNF (Supplemen a y Figu e 4a and 4b). The inhibi ion o RIPK1 ac i i y by nec os a in-1 educed HSP27 phospho yla ion simila ly o he loss o RIPK3 when ECs we e ea ed wi h VEGF-A (Figu e 6b). To de e mine i he signaling di e ences occu ed in i o a e umo cell injec ion, we injec ed mice wi h umo cells and a e 2, 6 and 12 h, he lungs we e homogenized o p o ein lysa es. Consis en wi h ou immo alized ECs, basal le els o phospho-p38 occu ed in he Ripk3 −/− lungs compa ed wi h wild- ype. A 2 h, phospho-p38 was up egula ed in wild- ype mice bu no in Ripk3 −/− mice (Figu e 6c). Taken oge he , ou da a show ha RIPK3 posi i ely egula es he ac i a ion o p38 and HSP27 upon pe meabili y ac o ea men (VEGF-A, VEGF-B, FGF-b) and he e o e p omo ing pe meabili y in he umo cells o me as asize (Figu e 6d). Discussion The cu en dogma is ha RIPK3 causes in lamma ion because o he induc ion o nec op osis. Howe e , ou Time (min) 41 41 41 41 DMSO Nec-1 23 23 phospho-p38 (S) p38 phospho-HSP27 (L) 0515 30 60 120 VEGF-A 0515 30 60 120 phospho-p38 (L) β-Ac in phospho-HSP27 (S) kDa kDa VEGF-B phospho-p38 p38 phospho-ERK1/2 ERK1/2 W Ripk3 -/- phospho-HSP27 PARP 41 125 41 41 41 32 93 41 53 RIPK3 β-Ac in 41 53 41 W Ripk3 -/- 0261202612B16-F10 phospho-p38 RIPK3 Time (hou s) β-Ac in kDa 0515 30 60 120 0515 30 60 120 Time (min) Figu e 6 RIPK1 kinase ac i i y and RIPK3 p omo es VEGF-dependen ac i a ion o p38/HSP27 MAP kinase signaling axis. (a) SV40 la ge T immo alized ECs isola ed om W o Ripk3 −/− mice we e ea ed wi h VEGF-B (10 ng/ml) and assayed o signaling by immunoblo analysis as indica ed. Rep esen a i e immunoblo is shown o n=3 expe imen s. (b) SV40 la ge T immo alized ECs isola ed om W mice we e ea ed wi h DMSO o nec os a in-1 (Nec-1) 1 h be o e VEGF-A (10 ng/ml) ea men and assayed o signaling by immunoblo analysis as indica ed. (c) Tumo cells we e injec ed in o mice a indica ed imepoin s and lungs we e lysed and immunoblo ed as indica ed. (S =sho exposu e, L =long exposu e). (d) P oposed model: RIPK1 kinase ac i i y and RIPK3 p omo e phospho yla ion o HSP27 in ECs upon pe meabili y ac o s imula ion RIPK1/RIPK3 p omo es ascula pe meabili y K Hänggi e al 8 Cell Dea h and Disease p e ious esul s sugges ha RIPK3 may al e cy okine elease, pa icula ly TNF in esponse o loss o IAPs. 24 We he e o e se ou o de e mine i RIPK3 may ha e a ole in he umo mic oen i onmen by p omo ing cy okine p oduc ion o causing nec op osis leading o umo p og ession. Ou esul s show RIPK3 did no al e umo g ow h o es ablished umo s. In addi ion, changes in cy okine p oduc ion in Ripk3 −/− mice compa ed wi h wild- ype mice a e umo injec ion we e minimal. The loss o kinase ac i i y o RIPK1 and he comple e loss o RIPK3 we e ound o be impo an in he abili y o he umo cells o o m lung nodules. Su p isingly, we did no ind Ripk3 K51A/K51A o Mlkl −/− mice exhibi ed a educ ion o umo nodules in he lung simila o Ripk3 −/− mice. Bone ma ow chime as showed he in ol emen o he s omal bu no he hema opoie ic compa men was c i ical o he loss o umo nodules in he lung in Ripk3 −/− mice. We hen ound he abili y o umo cells o ansmig a e h ough Ripk3 −/− endo helial ba ie o be de icien and ha cell dea h in he EC laye was independen o he geno ype when umo cells we e co- incuba ed. We unexpec edly ound he loss o RIPK3 o he kinase ac i i y o RIPK1 in he endo helial compa men we e de ec i e in p38/HSP27 signaling in esponse o pe meabili y ac o s such as VEGF-A. This lack o esponse esul ed in dec eased pe meabili y and essel sp ou ing in esponse o VEGF-A. These esul s sugges he ole o he nec osome is minimal in he ex a asa ion p ocess o umo cells and p esen s a no el ole o RIPK3 as a signaling pla o m downs eam o angiogenic ac o s such as VEGF and FGF. The cu en di icul y in assessing he ole o nec op osis in ela ed pa hologies o human in lamma o y disease is he absence o iden i ying ma ke s. The use o RIPK3 gene ic dele ion, pha macological inhibi ion o RIPK1 and/o co ela- i e e idence o RIPK3 p o ein o RNA up egula ion has been used o associa e he disease s a e wi h nec op osis. 35,36 Howe e , as RIPK1 has been shown o ha e al e na i e unc ion in egula ing apop osis and nec op osis 37–39 and also di ec ly in luencing in lamma ion, 24,40,41 u he downs eam e ec o s o nec op osis such as he use o Mlkl −/− mice a e equi ed o p o e he ole o nec op osis. 42 In ou expe imen s, he numbe o pulmona y umo nodules in he Mlkl −/− mice we e sligh ly educed compa ed wi h wild- ype mice bu no o he same ex en as in he Ripk3 −/− mice. I is unclea wha may be he eason o he di e ence in he umo nodule numbe s in he MLKL knock-ou mice we ob ained compa ed wi h S ilic e al. 25 , excep o he sou ce o he MLKL null mice. Ou da a also show ha he kinase ac i i y o RIPK1 has a ole in he abili y o umo nodules o o m in he lung. Ac i a ion o VEGFR2 by VEGF-A o VEGF-B causes phospho yla ion o c-S c and has been linked o inc eased pe meabili y by al e ing adhe ens junc ion o ma ion, VE-cadhe in. 33,43 c-S c has been shown o inhibi Fas-induced caspase-8 ac i a ion by phospho yla ion a Ty 380. 44 Fu he s udies a e equi ed o de e mine i RIPK1 and RIPK3 al e umo cell ex a asa ion as a complex wi h o wi hou caspase-8 in ol emen o i hese p o eins egula e di e en pa hways o esul in ascula pe meabili y. Vascula pe meabili y equi es issue emodeling simila o wound healing. Impai ed wound healing was ound in Ripk3 −/− mice compa ed wi h wild- ype mice, cha ac e ized by a dec eased MMP-9 p o ein exp ession and delayed CD31 + s aining and VEGF p oduc ion. 45 O he cy okines and g ow h ac o s we assayed, only MMP-9 was educed a 24 h in he Ripk3 −/− mice compa ed wi h wild- ype upon umo cell injec ion. The dec ease in MMP-9 p o ein le els co espond o an inc ease in neu ophil in il a ion o he lung a 24 h in he Ripk3 −/− , sugges ing an a emp o he immune sys em o compensa e o he lack o esponse in he endo helial compa men . The abili y o Ripk3 −/− monocy es o enhance ansmig a ion o umo cells h ough a wild- ype endo helial laye u he sugges s a de ec in he Ripk3 −/− ECs o espond o ex acellula cues. Indeed, he absence o RIPK3 educed signaling in esponse o VEGF-A, VEGF-B and FGF-b bu no TNF in he p38/HSP27 pa hway, a key pa hway in pe me- abili y. Ou esul s show ha he educed umo nodule o ma ion in RIPK3-de icien mice canno be a ibu ed o he ailu e o espond o one s imuli alone. In e es ingly, in Sei e e al. 22 , he loss o Mincle combined wi h he V12K-Ras PDA did no p o ec , as well as he loss o RIPK3, sugges ing addi ional ac o s may ha e a ole in he abili y o RIPK3 o o m PDA in a V12K-Ras model. Al e na i ely, he ole o RIPK3 may be mo e p e alen in issues ha e-model equen ly o issues ha mus unc ion as a ba ie o in ec ion. Fu he in es iga ion o o he pe meabili y ac o s in i o and whe he hese ligands can o m complexes o RIPK1/RIPK3 will be o in e es o de e mine i hese in acellula p o eins can be a ge ed o block se e al pa h- ways in ol ed in umo me as asis. Ripk3 −/− mice ha e no been epo ed o ha e any ascula de ec s du ing no mal de elopmen . In e es ingly, we epea - edly de ec inc eased basal phospho-p38 le els in un ea ed immo alized ECs and lung homogena es sugges ing he loss o RIPK3 is compensa ed du ing de elopmen and egula homeos asis. I appea s only du ing s ess such as wound healing o umo challenge, does RIPK3 become equi ed o he esponse o he addi ional s imuli. Changes a he basal le el in s uc u e o he essels o lung essel s uc u e ha e no been assessed and may p o ide insigh o why he Ripk3 −/− mice de elop wi h li le o no o e pheno ype. In summa y, ou s udy shows he kinase ac i i y o RIPK1 and RIPK3 has a physiological ole in he umo mic oen i on- men , in pa icula umo cell ex a asa ion and emodeling by al e ing he downs eam signaling pa hways o pe meabili y ac o s. This is a no el ole o he kinase ac i i y o RIPK1/ RIPK3 in addi ion o i s ole in egula ing nec op osis. In he con ex o in lamma ion and cell dea h, his suppo s p e ious epo s sugges ing he loss o kinase ac i i y o RIPK1 o he comple e loss o RIPK3 canno be used as an indica o o nec op osis and he po en ial o RIPK1/RIPK3 o be a signaling pla o m will need o be assessed in each disease model indi idually. Ma e ials and Me hods Animal wo k. Animals we e main ained unde op imized hygiene condi ions (OHB), and expe imen s we e app o ed by Zü ich Can onal Ve e ina y Commi ee in acco dance o he guidelines o he Swiss Animal P o ec ion Law (License 119/2012 and 186/2015). C57BL/6 mice we e pu chased om Jan ie Labs (F ance), Ripk3 −/− mice we e a kind gi om V Dixi , 46 SNP analyzed a N=7, Ripk1 K45A/K45A , Ripk3 K51A/K51A mice we e a kind gi om John Be in and Pe e J Gough om GlaxoSmi hKline (PA, USA), 26,40 Mlkl −/− mice we e ob ained om J Mu phy and W Alexande 10 (WEHI, Melbou ne, Aus alia). Mice we e injec ed wi h B16-F10 (2 × 10 5 cells) o MC-38 (3 × 10 5 cells) in a enously in 200 μl PBS o RIPK1/RIPK3 p omo es ascula pe meabili y K Hänggi e al 9 Cell Dea h and Disease