leupeptins and ursodoxicoltaurine

The endoplasmic reticulum (ER) plays a critical role in ensuring proper folding of newly synthesized proteins. Aberrant ER stress is reported to play a causal role in cardiovascular diseases. However, the effects of ER stress on vascular smooth muscle contractility and blood pressure remain unknown. The aim of this study was to investigate whether aberrant ER stress causes abnormal vasoconstriction and consequent high blood pressure in mice.. ER stress markers, vascular smooth muscle contractility, and blood pressure were monitored in mice. Incubation of isolated aortic rings with tunicamycin or MG132, 2 structurally unrelated ER stress inducers, significantly increased both phenylephrine-induced vasoconstriction and the phosphorylation of myosin light chain (Thr18/Ser19), both of which were abrogated by pretreatment with chemical chaperones or 5-Aminoimidazole-4-carboxamide ribonucleotide and metformin, 2 potent activators for the AMP-activated protein kinase. Consistently, administration of tauroursodeoxycholic acid or 4-phenyl butyric acid, 2 structurally unrelated chemical chaperones, in AMP-activated protein kinase-α2 knockout mice lowered blood pressure and abolished abnormal vasoconstrictor response of AMP-activated protein kinase-α2 knockout mice to phenylephrine. Consistently, tunicamycin (0.01 μg/g per day) infusion markedly increased both systolic and diastolic blood pressure, both of which were ablated by coadministration of 4-phenyl butyric acid. Furthermore, 4-phenyl butyric acid or tauroursodeoxycholic acid, which suppressed angiotensin II infusion-induced ER stress markers in vivo, markedly lowered blood pressure in angiotensin II-infused mice in vivo.. We conclude that ER stress increases vascular smooth muscle contractility resulting in high blood pressure, and AMP-activated protein kinase activation mitigates high blood pressure through the suppression of ER stress in vivo.

Topics: Aminoimidazole Carboxamide; AMP-Activated Protein Kinases; Angiotensin II; Animals; Antihypertensive Agents; Blood Pressure; Cells, Cultured; Disease Models, Animal; Dose-Response Relationship, Drug; Endoplasmic Reticulum Stress; Enzyme Activation; Enzyme Activators; Humans; Hypertension; Leupeptins; Mice; Mice, Knockout; Muscle, Smooth, Vascular; Myosin Light Chains; Nitric Oxide Synthase Type III; Phenylbutyrates; Phenylephrine; Phosphorylation; Ribonucleotides; Taurochenodeoxycholic Acid; Time Factors; Tunicamycin; Vasoconstriction; Vasoconstrictor Agents

Endoplasmic reticulum (ER) stress is associated with obesity-induced insulin resistance, yet the underlying mechanisms remain to be fully elucidated. Here we show that ER stress-induced insulin receptor (IR) down-regulation may play a critical role in obesity-induced insulin resistance. The expression levels of IR are negatively associated with the ER stress marker C/EBP homologous protein (CHOP) in insulin target tissues of db/db mice and mice fed a high-fat diet. Significant IR down-regulation was also observed in fat tissue of obese human subjects and in 3T3-L1 adipocytes treated with ER stress inducers. ER stress had little effect on IR tyrosine phosphorylation per se but greatly reduced IR downstream signaling. The ER stress-induced reduction in IR cellular levels was greatly alleviated by the autophagy inhibitor 3-methyladenine but not by the proteasome inhibitor N-benzoyloxycarbonyl (Z)-Leu-Leu-leucinal (MG132). Inhibition of autophagy prevented IR degradation but did not rescue IR downstream signaling, consistent with an adaptive role of autophagy in response to ER stress-induced insulin resistance. Finally, chemical chaperone treatment protects cells from ER stress-induced IR degradation in vitro and obesity-induced down-regulation of IR and insulin action in vivo. Our results uncover a new mechanism underlying obesity-induced insulin resistance and shed light on potential targets for the prevention and treatment of obesity-induced insulin resistance and type 2 diabetes.

Topics: 3T3-L1 Cells; Adipocytes; Animals; Autophagy; Disease Models, Animal; Down-Regulation; Endoplasmic Reticulum; Humans; Insulin Resistance; Leupeptins; Mice; Mice, Inbred Strains; Obesity; Phosphorylation; Receptor, Insulin; Taurochenodeoxycholic Acid; Tyrosine