Table 2.

Evidence for p38 MAPK involvement in psoriasis and psoriatic arthritis.

Diseases		References
Psoriasis	(1) p38 MAPK is phosphorylated in lesional psoriatic epidermis	[20–23]
	(2) Phosphorylated p38 is widely detectable in the keratinocyte nuclei indicative of the kinase strong participation in active gene expression	[21]
	(3) Among the p38 MAPK isoforms, p38alpha, p38beta, and p38delta are detectable in lesional psoriatic skin	[20]
	(4) p38-activated kinases MK-2 and MSK-1 are also phosphorylated in psoriatic lesional skin and regulate the production of proinflammatory cytokines such as TNF-α	[23–25]
	(5) Dual-specificity phosphatase 1 (DUSP1) is an important negative regulator of p38 MAPK activity DUSP1 mRNA expression is downregulated in psoriatic skin lesions compared with paired samples of nonlesional psoriatic skin	[26]
	(6) p38-MAPK induced Ser727 phosphorylation of STAT-1 and STAT-3 is detected in psoriatic skin	[27, 28]
	(7) p38-MAPK-dependent expression of cathelicidin antimicrobial peptide, human β-defensin-2, human β-defensin-3, S100A7, and S100A8	[29, 30]
Psoriatic arthritis	(1) Phosphorylated p38 MAPK is detectable in both lining and sublining synovial area	[31]
	(2) P38 positive cells are also detected in inflammatory infiltrates, in perivascular zones, and in the endothelium	[31]
	(3) IL-36α is upregulated in PsA and RA synovia and leads to IL-6 and IL-8 production by synovial fibroblasts through p38/NFkB activation	[32]