Specific AMPK Inhibitor Research Articles

AMP-activated Protein Kinase Contributes to UV- and H2O2-induced Apoptosis in Human Skin Keratinocytes

AMP-activated protein kinase or AMPK is an evolutionarily conserved sensor of cellular energy status, activated by a variety of cellular stresses that deplete ATP. However, the possible involvement of AMPK in UV- and H(2)O(2)-induced oxidative stresses that lead to skin aging or skin cancer has not been fully studied. We demonstrated for the first time that UV and H(2)O(2) induce AMPK activation (Thr(172) phosphorylation) in cultured human skin keratinocytes. UV and H(2)O(2) also phosphorylate LKB1, an upstream signal of AMPK, in an epidermal growth factor receptor-dependent manner. Using compound C, a specific inhibitor of AMPK and AMPK-specific small interfering RNA knockdown as well as AMPK activator, we found that AMPK serves as a positive regulator for p38 and p53 (Ser(15)) phosphorylation induced by UV radiation and H(2)O(2) treatment. We also observed that AMPK serves as a negative feedback signal against UV-induced mTOR (mammalian target of rapamycin) activation in a TSC2-dependent manner. Inhibiting mTOR and positively regulating p53 and p38 might contribute to the pro-apoptotic effect of AMPK on UV- or H(2)O(2)-treated cells. Furthermore, activation of AMPK also phosphorylates acetyl-CoA carboxylase or ACC, the pivotal enzyme of fatty acid synthesis, and PFK2, the key protein of glycolysis in UV-radiated cells. Collectively, we conclude that AMPK contributes to UV- and H(2)O(2)-induced apoptosis via multiple mechanisms in human skin keratinocytes and AMPK plays important roles in UV-induced signal transduction ultimately leading to skin photoaging and even skin cancer.

UV and H2O2 induce AMPK activation in cultured skin keratinocytes

AMP‐activated protein kinase or AMPK is an evolutionarily conserved sensor of cellular energy status, activated by a variety of cellular stresses that deplete ATP as well as other stresses. However, the possible involvement of AMPK in UV‐ and H2O2 ‐induced skin aging is not fully studied. We show for the first time that UV and H2O2 induce AMPK activation in cultured human skin keratinocytes (HaCaT cells). UV and H2O2 also induce LKB1, the possible upstream signal of AMPK, in an EGFR dependent manner. Using Compound C, a specific inhibitor of AMPK and AMPK specific siRNA knockdown as well as AMPK activator AICAR, we found that AMPK serves as a positive regulator for p38 and p53 (ser 15) activation induced by UV radiation or H2O2 treatment. We also observed that AMPK activation pathway serves a negative feedback signal pathway against UV‐induced mTOR activation in a TSC2 dependent manner. Inhibiting mTOR and activating p53 and p38 may mediate AMPK's pro‐apoptotic effect in UV or H2O2 treated cells. Furthermore, activation AMPK also phosphorylates acetyl‐CoA carboxylase or ACC, the pivotal enzyme of fatty acid synthesis, and PFK2, the key protein of glycolysis in UV‐radiated cells which may explain reduced adipogenesis in UV or H2O2 treated 3T3‐L1 adipocyte and skin keratinocytes. Collectively, our results demonstrate that UV and H2O2 induce EGFR/LKB1/AMPK signal pathway activation in cultured skin keratinocytes, which plays important role on UV or H2O2‐induced signal transduction and skin aging.

Compound C, an inhibitor of AMP-activated protein kinase, inhibits glycolysis in mouse longissimus dorsi postmortem

Pale, soft, and exudative (PSE) meat has been recognized for decades and causes huge economic loss to the meat industry due to its inferior quality. Although it has been well established that fast and excessive glycolysis combined with high temperature in muscle early postmortem is the cause of PSE meat, the molecular mechanisms associated with this abnormal glycolysis remain poorly defined. Our previous studies with mice and pigs suggest that AMPK regulates muscle glycolysis postmortem. To confirm further the role of AMPK in the regulation of postmortem glycolysis, we investigated the effects of intraperitoneal injection of compound C, a specific AMPK inhibitor, on AMPK activation and glycolysis in postmortem longissimus dorsi (LD) muscle of mice. Data showed that intraperitoneal injection of compound C inhibited AMPK activation in postmortem mouse LD muscle. Simultaneously, injection of compound C inhibited glycolysis and increased muscle pH corroborating of our previous observations that postmortem glycolysis is inhibited in AMPK knockout mice. This study firmly supports that AMPK regulates glycolysis in postmortem skeletal muscle and suggests that AMPK can be a target to control postmortem glycolysis, preventing incidence of PSE meat.