Metformin protects against diclofenac-induced toxicity in primary rat
hepatocytes by preserving mitochondrial integrity via a pathway
involving EPAC
Abstract
Background and Purpose: We have previously shown that the antidiabetic
drug metformin protects hepatocytes against toxicity by various
stressors. Chronic or excessive consumption of diclofenac (DF), a
pain-relieving drug, leads to drug-induced liver injury via a mechanism
involving mitochondrial damage and ultimately apoptotic death of
hepatocytes. However, whether metformin protects against DF-induced
toxicity is unknown. Recently, we have shown that cAMP elevation is
protective against DF-induced apoptotic death in hepatocytes, a
protective effect primarily involving the downstream cAMP effector EPAC
and preservation of mitochondrial function. This study aimed to
investigate whether metformin protects against DF-induced toxicity via
cAMP-EPACs. Experimental Approach: Primary rat hepatocytes were exposed
to 400 µmol/L DF. CE3F4 or ESI-O5 were used as EPAC-1 or 2 inhibitors,
respectively. Apoptosis was measured by caspase-3 activity and necrosis
by Sytox green staining. Seahorse X96 assay was used to determine
mitochondrial function. Mitochondrial reactive oxygen species (ROS)
production was measured using MitoSox, mitochondrial MnSOD expression by
immunostaining and mitochondrial morphology (fusion and fission ratio)
by 3D refractive index imaging. Key Results: Metformin (1 mmol/L) was
protective against DF-induced apoptosis in hepatocytes. This protective
effect was EPAC-dependent (mainly EPAC-2). Metformin restored
mitochondrial morphology in an EPAC-independent manner. DF-induced
mitochondrial dysfunction demonstrated by decreased oxygen consumption
rate, increased ROS production, and a reduced MnSOD level were all
reversed by metformin in an EPAC-dependent manner. Conclusion and
Implications: Metformin protects hepatocytes against DF-induced toxicity
via cAMP-dependent EPAC-2. Data available on request from the authors.