Department of Dermatology, Ehime University School of Medicine, Japan.
J Dermatol Sci. 2010 Dec;60(3):179-86. doi: 10.1016/j.jdermsci.2010.09.008. Epub 2010 Oct 23.
Production of antimicrobial peptides (AMPs) is the primary mechanism by which skin innate immunity protects against infection. Hormonally active vitamin D3 (1α,25-dihydroxyvitamin D3; 1,25D₃) is a vital regulator of skin innate immunity, and has been shown to increase the expression and function of AMPs.
PPARγ is a ligand-activated nuclear receptor and plays a role in keratinocyte differentiation and cutaneous homeostasis. In this study, we investigate whether 1,25D₃-activated PPARγ signaling regulates AMP expression in keratinocytes.
Subconfluent keratinocytes were treated with 1,25D₃ for the indicated times. The mRNA and protein levels of AMPs were detected by RT-PCR and Western blot, and the DNA binding activation of PPARγ, VDRE and AP-1 was investigated by EMSA. To examine the role of PPARγ, the recombinant adenovirus carrying a dominant-negative form of PPARγ (dn-PPARγ) was constructed and transfected into keratinocytes.
We show here that 1,25D₃ significantly enhances hBD-3 and cathelicidin expression in keratinocytes. Expression of dn-PPARγ did not affect binding to the vitamin D-responsive element (VDRE), which is crucial for cathelicidin induction by VD3; however, it did decrease 1,25D₃ induction of both hBD-3 and cathelicidin. Inhibition of the p38, ERK, and JNK signaling pathways blocked hBD-3 expression, whereas only p38 inhibition suppressed cathelicidin induction. dn-PPARγ had no effect on ERK and JNK activity, but inhibited p38 phosphorylation and suppressed 1,25D₃-induced AP-1 activation via effects on Fra1 and c-Fos proteins.
In conclusion, PPARγ regulates the 1,25D₃-induced hBD-3 and cathelicidin expression in keratinocytes through the regulation of AP-1 and p38 activity.
抗菌肽（AMPs）的产生是皮肤固有免疫抵抗感染的主要机制。具有生物活性的维生素 D3（1α，25-二羟维生素 D3；1，25D₃）是皮肤固有免疫的重要调节剂，并且已经显示出可以增加 AMP 的表达和功能。
过氧化物酶体增殖物激活受体γ（PPARγ）是一种配体激活的核受体，在角质形成细胞分化和皮肤稳态中发挥作用。在这项研究中，我们研究了 1，25D₃激活的 PPARγ 信号是否调节角质形成细胞中的 AMP 表达。
将亚汇合的角质形成细胞用 1，25D₃处理指定的时间。通过 RT-PCR 和 Western blot 检测 AMP 的 mRNA 和蛋白水平，并通过 EMSA 研究 PPARγ、VDRE 和 AP-1 的 DNA 结合激活。为了研究 PPARγ 的作用，构建了携带显性失活形式的 PPARγ（dn-PPARγ）的重组腺病毒，并转染角质形成细胞。
我们在此表明，1，25D₃可显著增强角质形成细胞中 hBD-3 和 cathelicidin 的表达。dn-PPARγ 的表达不影响维生素 D 反应元件（VDRE）的结合，这对于 VD3 诱导 cathelicidin 至关重要；然而，它确实降低了 1，25D₃对 hBD-3 和 cathelicidin 的诱导。抑制 p38、ERK 和 JNK 信号通路阻断了 hBD-3 的表达，而仅抑制 p38 抑制了 cathelicidin 的诱导。dn-PPARγ 对 ERK 和 JNK 活性没有影响，但通过 Fra1 和 c-Fos 蛋白抑制 p38 磷酸化并抑制 1，25D₃诱导的 AP-1 激活。
总之，PPARγ 通过调节 AP-1 和 p38 活性来调节 1，25D₃ 诱导的角质形成细胞中 hBD-3 和 cathelicidin 的表达。
