The miRNA that can burn you!

This is not strictly a genomics topic, but it's summer time and for me this means hot sun and sunburns... So it's hard to ignore this paper from Nature Medicine that casts light on why a funny day at the beach can results in a couple of day of pain (at least for me when I forget my sun protection lotion)... Authors show that all the pain comes from a miRNA (these little molecules play a role really everywhere!) that is sensitive to UV-B exposure. Nearby cells sense the damaged miRNA and trigger inflammatory response. Really a hot topic!

Ultraviolet radiation damages self noncoding RNA and is detected by TLR3.

Bernard JJ, Cowing-Zitron C, Nakatsuji T, Muehleisen B, Muto J, Borkowski AW, Martinez L, Greidinger EL, Yu BD, Gallo RL.

SourceAbstract

Abstract

Exposure to ultraviolet B (UVB) radiation from the sun can result in sunburn, premature aging and carcinogenesis, but the mechanism responsible for acute inflammation of the skin is not well understood. Here we show that RNA is released from keratinocytes after UVB exposure and that this stimulates production of the inflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) from nonirradiated keratinocytes and peripheral blood mononuclear cells (PBMCs). Whole-transcriptome sequencing revealed that UVB irradiation of keratinocytes induced alterations in the double-stranded domains of some noncoding RNAs. We found that this UVB-damaged RNA was sufficient to induce cytokine production from nonirradiated cells, as UVB irradiation of a purified noncoding RNA (U1 RNA) reproduced the same response as the one we observed to UVB-damaged keratinocytes. The responses to both UVB-damaged self-RNAs and UVB-damaged keratinocytes were dependent on Toll-like receptor 3 (TLR3) and Toll-like receptor adaptor molecule 1 (TRIF). In response to UVB exposure, Tlr3(-/-) mice did not upregulate TNF-α in the skin. Moreover, TLR3 was also necessary for UVB-radiation-induced immune suppression. These findings establish that UVB damage is detected byTLR3 and that self-RNA is a damage-associated molecular pattern that serves as an endogenous signal of solar injury.