microRNA-25 targets PKCζ and protects osteoblastic cells from dexamethasone via activating AMPK signaling

Abstract

AMP-activated protein kinase (AMPK) activation could protect osteoblasts from dexamethasone (Dex). This study aims to provoke AMPK activation via microRNA downregulation of its negative regulator protein kinase C ζ (PKCζ). Results show that microRNA-25-5p (miR-25-5p) targets PKCζ's 3’ untranslated regions (UTRs). Forced-expression of miR-25 downregulated PKCζ and activated AMPK in human osteoblastic cells (OB-6 and hFOB1.19 lines), which thereafter protected cells from Dex. Reversely, expression of antagomiR-25, the miR-25 inhibitor, upregulated PKCζ and inhibited AMPK activation, exacerbating Dex damages. Notably, PKCζ shRNA knockdown similarly activated AMPK and protected osteoblastic cells from Dex. AMPK activation was required for miR-25-induced osteoblastic cell protection. AMPKα shRNA or dominant negative mutation almost completely blocked miR-25-induced cytoprotection against Dex. Further studies showed that miR-25 expression increased NADPH activity and suppressed Dex-induced oxidative stress in osteoblastic cells. Such effects by miR-25 were abolished with AMPKα knockdown or mutation. Significantly, miR-25-5p level was increased in patients’ necrotic femoral head tissues, which was correlated with PKCζ downregulation and AMPK hyper-activation. These results suggest that miR-25-5p targets PKCζ and protects osteoblastic cells from Dex possibly via activating AMPK signaling.

Silencing protein kinase C ζ by microRNA-25-5p activates AMPK signaling and inhibits colorectal cancer cell proliferation

“…Recent studies have proposed protein kinase C ζ (PKCζ) as a negative regulator of AMPK [ 23 , 24 ]. PKCζ was shown to phosphorylate and inactivate the AMPK kinase liver kinase B1 (LKB1), thus shutting down AMPK signaling [ 23 , 24 ]. Reversely, PKCζ silence or inhibition could result in sustained AMPK activation [ 23 , 24 ].…”

“…PKCζ was shown to phosphorylate and inactivate the AMPK kinase liver kinase B1 (LKB1), thus shutting down AMPK signaling [ 23 , 24 ]. Reversely, PKCζ silence or inhibition could result in sustained AMPK activation [ 23 , 24 ]. Here, we show that PKCζ upregulation in human CRC cells silences AMPK to promote cancer cell proliferation.…”

“…Here, we show that PKCζ upregulation in human CRC cells silences AMPK to promote cancer cell proliferation. Further, downregulation of microRNA-25-5p (“miR-25-5p”), a PKCζ-targeting miRNA [ 24 ], could be the cause of PKCζ upregulation in CRC cells.…”

microRNA-455 targets cullin 3 to activate Nrf2 signaling and protect human osteoblasts from hydrogen peroxide

“…Data were expressed as the mean ± SD [ 45 , 57 ]. Comparisons between groups were performed via one-way ANOVA and then Student-Newman-Keuls test (SPSS 18.0).…”

Noncoding RNAs in Steroid-Induced Osteonecrosis of the Femoral Head

“…In addition, AMPK knockdown or mutation abolished this miR-135b-induced cytoprotection against steroid treatment in osteoblastic cells, supporting a critical function of AMPK activation in the actions of miR-135b. Subsequently, they found that miR-25-5p level was increased in patients' necrotic femoral head tissues, targeting and downregulating PKCζ in osteoblastic cells and in turn activating AMPK signaling and protecting cells against the damage induced by steroids [40].…”