Sphingoid Base-Upregulated Caspase-14 Expression Involves MAPK.

Sphingolipids are putative intracellular signal mediators in cell differentiation, growth inhibition, and apoptosis. Especially, sphingoid base-backbones of sphingolipids (sphingosine, sphinganine, and phytosphingosine) and their metabolites N-acyl-sphingoid bases (ceramides) are highly bioactive. In skin, one of the caspases, caspase-14, is expressed predominantly in cornifying epithelia, and caspase-14 plays an important role in keratinocyte differentiation. As ceramides were surrounding lipids in the keratinocytes and ceramides stimulate keratinocyte differentiation, we therefore examined the upregulation of caspase-14 by various sphingoid bases and ceramide. Sphingosine, sphinganine, phytosphingosine, and C2-ceramide treatment at the doses not damaging cells significantly increased caspase-14 mRNA and protein expression in dose-dependent manner on human keratinocyte HaCaT cells. These results indicated that sphingoid bases and ceramide upregulated caspase-14 mRNA to increase intracellular caspase-14 protein level. We next examined the caspase-14 upregulation mechanism by sphingoid bases. We used the most effective sphingoid base, phytosphingosine, and revealed that specific inhibitors of the mitogen-activated protein kinase, p38 and c-jun N-terminal protein kinase (JNK), blocked caspase-14 expression. This indicates that phytosphingosine upregulation of caspase-14 is involved of p38 and JNK activation. Moreover, phytosphingosine induced caspase-14 upregulation in vivo, suggesting that sphingoid bases were involved in keratinocyte differentiation by affecting caspase-14.

Ashwagandha root extract exerts anti­inflammatory effects in HaCaT cells by inhibiting the MAPK/NF­κB pathways and by regulating cytokines.

A paste composed of the boiled leaves and roots of the Ashwagandha plant is used to cure ulcer and swelling in Ayurvedic medicine. However, the effects of the hot water extract of Ashwagandha roots (ASH­WEX), which is also used in Ayurveda, on skin have not been fully elucidated. Therefore, the present study investigated the anti­inflammatory activity of ASH­WEX on skin, by using the human keratinocyte cell line HaCaT. The results indicated that ASH­WEX significantly inhibited mRNA expression of inflammatory cytokines, including interleukin (IL)­8, IL­6, tumor necrosis factor (TNF­α), IL­1ß and IL­12, and promoted the mRNA expression of the anti­inflammatory cytokine transforming growth factor (TGF)­ß1 in HaCaT cells. In addition, ASH­WEX inhibited the lipopolysaccharide­induced phosphorylation of p38 and c­Jun N­terminal kinase, as well as the nuclear translocation of nuclear factor (NF)­κB p65. Downregulation of TNF­α mRNA and upregulation of TGF­ß1 mRNA were also observed in vivo following ASH­WEX treatment of mouse skin. In conclusion, the present study demonstrated that the anti­inflammatory effect of ASH­WEX may be due to its ability to suppress the NF­κB and mitogen­activated protein kinase pathways, and to modulate cytokine expression. These results suggest that ASH­WEX can potentially protect against skin inflammation.