title: Cannabinoid receptor 1 mediates high glucose-induced apoptosis via endoplasmic reticulum stress in primary cultured rat mesangial cells.
abstract: The endocannabinoid system in animals and humans is involved in the onset of diverse diseases, including obesity and diabetic nephropathy, which is a major end-stage renal disease characterized by high glucose (HG)-induced apoptosis of mesangial cells. Endocannabinoids induce physiological and behavioral effects by activating two specific receptors, cannabinoid receptor 1 (CB(1)R) and cannabinoid receptor 2 (CB(2)R). However, the pathophysiology of CB(1)R in diabetic nephropathy has not been elucidated. We investigated the effects of HG on CB(1)R expression and its signaling pathways in primary cultured rat mesangial cells. HG significantly increased CB(1)R mRNA and protein levels in a time-dependent manner and induced CB(1)R internalization. NF-κB and cPLA(2) were involved in the HG-induced increase in CB(1)R levels. Using a CB(1)R antagonist (AM251) and CB(1) siRNA transfection, we showed that HG-induced CB(1)R is linked to apoptosis. Specifically, HG inhibited the expression of GRP78, but induced increases in endoplasmic reticulum (ER) stress proteins, including phosphorylated (p)-protein kinase-like ER-associated kinase, p-eukaryotic initiation factor 2α, p-activating transcription factor-4, and C/EBP homologous protein. In addition, HG increased the Bax/Bcl-2 ratio and increased the amounts of cleaved poly(ADP-ribose) polymerase and caspase-3. These apoptotic effects were prevented by AM251 and by the downregulation of CB(1)R expression by small interfering RNA. We propose a mechanism by which blockade of CB(1)R attenuates HG-induced apoptosis in rat mesangial cells. Our findings suggest that blockade of CB(1)R may be a potential therapy in diabetic nephropathy.
authors.affiliation: Bio-therapy Human Resources Center, Dept. of Veterinary Physiology, College of Veterinary Medicine, Chonnam National University, Kwangju 500-757, Korea.
authors.forename: Jae Cheong
authors.initials: JC
authors.lastname: Lim
authors.forename: Seul Ki
authors.initials: SK
authors.lastname: Lim
authors.forename: Min Jung
authors.initials: MJ
authors.lastname: Park
authors.forename: Gye Yeop
authors.initials: GY
authors.lastname: Kim
authors.forename: Ho Jae
authors.initials: HJ
authors.lastname: Han
authors.forename: Soo Hyun
authors.initials: SH
authors.lastname: Park
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004396:Coloring Agents; D003600:Cytosol / Q000187:drug effects / Q000502:physiology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000502:physiology*; D000091342:Endoplasmic Reticulum Chaperone BiP; D005455:Fluorescent Antibody Technique; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D005947:Glucose / Q000494:pharmacology*; D008297:Male; D016328:NF-kappa B / Q000502:physiology; D054467:Phospholipases A2 / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000302:isolation & purification; D034741:RNA, Small Interfering; D051381:Rats; D017207:Rats, Sprague-Dawley; D043884:Receptor, Cannabinoid, CB1 / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013312:Stress, Physiological / Q000187:drug effects
chemical_list: D000199:Actins; D004396:Coloring Agents; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D016328:NF-kappa B; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D043884:Receptor, Cannabinoid, CB1; D054467:Phospholipases A2; D005947:Glucose