The high glucose-induced stimulation of B1R and B2R expression via CB1R activation is involved in rat podocyte apoptosis

Abstract: Aims: We examined renal kallikrein–kinin system (KKS) apoptosis and its related signaling pathway in rat podocytes. In addition, we studied the relationship of cannabinoid receptor 1 (CB1R) with high glucose and BK receptors. Main methods: Cell viability was determined by an MTT assay and apoptosis by DNA fragmentation assay, while gene expression was investigated by RT-PCR. Protein expression was analyzed by Western blot analysis. A chemical inhibitor or siRNA transfection was used to inhibit B1R, B2R, and CB1R signaling. Key findings: High glucose (25mM) treatment decreased cell viability and increased DNA fragmentation. High glucose-induced DNA fragmentation and PARP and caspase-3 activations were blocked by both [des-Arg10]-HOE 140 (a B1R antagonist) and HOE 140 (a B2R antagonist). High glucose also increased Akt phosphorylation, ER stress-related protein expression, and NF-κB/I-κB phosphorylation in podocytes, which was blocked by both [des-Arg10]-HOE 140 and HOE 140. In addition, B1R and B2R siRNA transfections prevented high glucose-induced Akt and NF-κB activations in rat podocytes. Moreover, AM251 (a CB1R antagonist) treatment and CB1R siRNA transfection blocked the high glucose-induced stimulation of BK receptor expression, Akt activation, and NF-κB activation. Significance: Our study suggests that hyperglycemia induces apoptosis via the stimulation of B1R and B2R expression through CB1R activation in rat podocytes in vitro, which is associated with the development of diabetic nephropathy. [Copyright &y& Elsevier]