The precise mechanism through which macroautophagy/autophagy affects
psoriasis is poorly understood. Here, we found that keratinocyte (KC) autophagy, which was positively correlated with psoriatic severity in patients and mouse models and could be inhibited by
mitogen-activated protein kinase (MAPK) family inactivation. The impairment of autophagic flux alleviated psoriasisform
inflammation. We also found that an autophagy-based unconventional secretory pathway (autosecretion) dependent on ATG5 (autophagy related 5) and GORASP2 (golgi reassembly stacking
protein 2) promoted psoriasiform KC
inflammation. Moreover, the
alarmin HMGB1 (high mobility group box 1) was more effective than other autosecretory
proteins in regulating psoriasiform cutaneous
inflammation.
HMGB1 neutralization in autophagy-efficient KCs eliminated the differences in psoriasiform
inflammation between Krt14+/+-Atg5f/f KCs and Krt14Cre/+-atg5f/f KCs, and conversely, recombinant
HMGB1 almost completely restored psoriasiform
inflammation in Krt14Cre/+-atg5f/f KCs in vivo. These results suggest that HMGB1-associated autosecretion plays a pivotal role in cutaneous inflammation. Finally, we demonstrated that Krt14Cre/+-hmgb1f/f mice displayed attenuated psoriatic inflammation due to the essential crosstalk between KC-specific HMGB1-associated autosecretion and γδT cells. Thus, this study uncovered a novel autophagy mechanism in
psoriasis pathogenesis, and the findings imply the clinical significance of investigating and treating
psoriasis.Abbreviations: 3-MA: 3-methyladenine; ACTB: actin beta; AGER: advanced glycosylation end-product specific receptor; Anti-
HMGB1: anti-HMGB1
neutralizing antibody; Anti-
IL18: anti-IL18
neutralizing antibody; Anti-IL1B: anti-IL1B
neutralizing antibody; ATG5: autophagy related 5; BAF:
bafilomycin A1; BECN1:
beclin 1;
CASP1: caspase 1; CCL: C-C motif
chemokine ligand; CsA:
cyclosporine A; ctrl
shRNA: lentivirus harboring
shRNA against control; CXCL: C-X-C motif
chemokine ligand; DCs: dendritic cells; DMEM: dulbecco's modified Eagle's medium; ELISA:
enzyme-linked
immunosorbent assay; EM: electron microscopy; FBS:
fetal bovine serum; GORASP2
shRNA: lentivirus harboring
shRNA against GORASP2; GORASP2/GRASP55: golgi reassembly stacking
protein 2; GR1: a composite
epitope between LY6 (lymphocyte
antigen 6 complex) locus C1 and LY6 locus G6D
antigens; H&E:
hematoxylin and
eosin;
HMGB1: high mobility group box 1;
HMGB1 shRNA: lentivirus harboring
shRNA against
HMGB1; IFNG/IFN-γ:
interferon gamma; IL17A:
interleukin 17A;
IL18:
interleukin 18; IL1A/IL-1α:
interleukin 1 alpha; IL1B/IL-1β:
interleukin 1 beta; IL22/IL-22:
interleukin 22; IL23A:
interleukin 23 subunit alpha; IL23R:
interleukin 23 receptor; IMQ:
imiquimod; ITGAM/CD11B:
integrin subunit alpha M; ITGAX/CD11C:
integrin subunit alpha X; IVL:
involucrin; KC: keratinocyte; KD: knockdown; KO: knockout; Krt14+/+-Atg5f/f mice: mice bearing an Atg5 flox allele, in which exon 3 of the Atg5 gene is flanked by two loxP sites; Krt14+/+-Hmgb1f/f: mice bearing an
Hmgb1 flox allele, in which exon 2 to 4 of the
Hmgb1 gene is flanked by two loxP sites; Krt14Cre/+-atg5f/f mice: keratinocyte-specific atg5 knockout mice generated by mating Atg5-floxed mice with mice expressing
Cre recombinase under the control of the promoter of Krt4; Krt14Cre/+-hmgb1f/f mice: keratinocyte-specific
hmgb1 knockout mice generated by mating Hmgb1-floxed mice with mice expressing
Cre recombinase under the control of the promoter of Krt14; Krt14-Vegfa mice: mice expressing 164-amino
acid Vegfa splice variant
recombinase under the control of promoter of Krt14; LAMP1:
lysosomal associated membrane protein 1; LDH:
lactate dehydrogenase;
LORICRIN:
loricrin cornified envelope precursor
protein; M5: TNF, IL1A, IL17A, IL22 and OSM in combination; MAP1LC3/LC3:
microtubule associated protein 1 light chain 3; MAPK:
mitogen-activated protein kinase; MKI67: marker of proliferation Ki-67; MTT:
thiazolyl blue tetrazolium bromide; NFKB/NF-κB:
nuclear factor kappa B; NHEKs: primary normal human epidermal keratinocytes; NS: not significant; OSM:
oncostatin M; PASI:
psoriasis area and severity index; PtdIns3K: class III
phosphatidylinositol 3-kinase; qRT-PCR: quantitative RT-PCR; RELA/p65: RELA proto-oncogene,
NF-kB subunit; rHMGB1: recombinant
HMGB1; rIL18: recombinant
interleukin 18; rIL1B: recombinant
interleukin 1 beta; S100A: S100
calcium binding protein A; SQSTM1/p62: sequestosome 1; T17: IL17A-producing T; TCR:
T-cell receptor; tcrd KO mice: tcrd (
T cell receptor delta chain) knockout mice, which show deficient receptor expression in all adult lymphoid and epithelial organs; TLR:
toll-like receptor; TNF/TNF-α:
tumor necrosis factor; WOR:
wortmannin; WT: wild-type; γδT17 cells: IL17A-producing γδ T cells.