miR‐495 promotes intestinal epithelial cell apoptosis through downregulation of Sphingosine‐1‐phosphate.

Many pathological conditions lead to defects in intestinal epithelial integrity and loss of barrier function; Sphingosine‐1‐phosphate (S1P) has been shown to augment intestinal barrier integrity, though the exact mechanisms are not completely understood. We have previously shown that overexpression of Sphingosine Kinase 1 (SphK1), the rate limiting enzyme for S1P synthesis, significantly increased S1P production and cell proliferation. Here we show that microRNA 495 (miR‐495) upregulation led to decreased levels of SphK1 resultant from a direct effect at the SphK1 mRNA. Increasing expression of miR‐495 in intestinal epithelial cells resulted in decreased proliferation and increased susceptibility to apoptosis. Transgenic expression of miR‐495 inhibited mucosal growth, as well as decreased proliferation in the crypts. The intestinal villi also expressed decreased levels of barrier proteins and exaggerated damage upon exposure to cecal ligation‐puncture. These results implicate miR‐495 as a critical negative regulator of intestinal epithelial protection and proliferation through direct regulation of SphK1, the rate limiting enzyme critical for production of S1P. [ABSTRACT FROM AUTHOR]