Glucose concentration in culture medium affects mRNA expression of TRPV1 and CB1 receptors and changes capsaicin toxicity in PC12 cells

Objective (s):Hyperglycemia is widely recognized as the underlying cause for some debilitating conditions in diabetic patients. The role of cannabinoid CB1 and vanilloid TRPV1 receptors and their endogenous agonists, endovanilloids, in diabetic neuropathy is shown in many studies. Here we have used PC12 cell line to investigate the possible influence of glucose concentration in culture medium on cytoprotective or toxic effects of a CB1 [WIN55 212-2 (WIN)], or TRPV1 [Capsaicin (CAS)] agonist. Cell viability was tested using the MTT assay. We have also measured TRPV1 and CB1 transcripts by real time reverse transcription-polymerase chain reaction while cells were grown in low (5.5 mM) and high (50 mM) glucose concentrations. Real time PCR results indicated that high glucose medium increased (P<0.01) TRPV1 mRNA and decreased (P <0.001) that of CB1. Cell culture tests show that hyperglycemic cells are more vulnerable (Dose × Medium, F (3,63)=41.5, P<0.001) to the toxic effects of capsaicin compared to those grown in low glucose medium. These findings propose that hyperglycemic conditions may result in neuronal cell death because of inducing a counterbalance between cytotoxic TRPV1 and cytoprotective CB1 receptors.