A mechanism underlying hypertensive occurrence in the metabolic syndrome: cooperative effect of oxidative stress and calcium accumulation in vascular smooth muscle cells.

Several lines of evidence indicate that reactive oxygen species (ROS) overproduction under the metabolic syndrome condition is the leading cause of cardiovascular events. Calcium is an important stimulus for vasoconstriction and plays a pivotal role in the development of hypertension. Here, we investigate whether a relationship exists between metabolic syndrome-induced mitochondrial ROS overproduction and Ang II-mediated Ca2+ release in vascular smooth muscle cells (VSMC). The effect of mitochondrial ROS on AT1 expression, and Ca2+ and IP3 generation was studied in 2 VSMC models of metabolic syndrome using fura-2/AM probes and ELISA-based assay. Ang II-mediated aortic ring contraction in SD rats fed with high-fat diet (HFD) was measured using a force transducer connected to chart recorder. In the metabolic syndrome, almost 2-fold increased mitochondrial O2 - significantly upregulated AT1 expressions by ~60%, companied by elevated Ca2+ and IP3 levels in VSMC and enhanced aortic rings contraction. All these increments were blocked by rotenone (inhibitor of mitochondrial respiratory chain complex I), ruthenium red (inhibitor of calcium uniporter), cyclosporin A (inhibitor of mitochondrial permeability pore), and N-acetylcysteine. Therefore, in the states of metabolic syndrome, ROS overproduction in mitochondrial complex I enhances Ang II-mediated vascular contraction via an AT1-dependent pathway. In addition, the import of Ca2+ from endoplasmic reticulum to mitochondria via calcium uniporter and mitochondrial permeability pore seems to serve as a mechanism to further aggravate mitochondrial damage and vascular dysfunction that may contribute to the occurrence of hypertension.

Extracellular redox state regulates catecholamine biosynthesis in PC12 cells with insulin resistance.

Extracellular cysteine (Cys)/cystine (CySS) redox potential (Eh) plays a crucial role in maintaining redox homeostasis and an alteration of redox state occurs in various physiological conditions, including diabetes, cancer, and aging. This study was designed to determine whether a variation in extracellular redox state would alter the function of insulin-resistant PC12 cells. Various redox states were established by providing different extracellular Cys/CySS Eh to insulin-resistant PC12 cells. We intensively investigated the relationship between redox state and catecholamine biosynthesis in PC12 cells, and evaluated the changes in cellular reactive oxygen species (ROS), catecholamine (CA) synthesis, tyrosine hydroxylase (TH) expressions, and the activity of rate-limiting enzyme in CA synthesis by using DCF-fluorescence, HPLC, and the real-time PCR, respectively. We also determined the protein levels of NF-E2-related factor 2 (Nrf2), a redox sensitive transcription factor, using an ELISA assay. We found that the oxidized Cys/CySS Eh (0 mV) pretreatment decreased CA, TH, and Nrf2 levels, but induced ROS overproduction. Insulin induced a significant increase in CA synthesis and ROS production, blocked by more reducing redox conditions. The paradox of CA and TH alterations between insulin and 0 mV groups may be attributed to degree of redox imbalance as evidenced by different ROS levels in 2 groups, which is further confirmed by CA alterations in different concentrations of hydrogen peroxide. Additionally, dithiole-3-thione (D3T, an inducer of Nrf2) corrected 0 mV-induced TH inhibition. In conclusion, CA biosynthesis in insulin-resistant PC12 cells could be influenced by extracellular Cys/CySS redox effects on cellular redox sensitive transcription factors.

Effect and mechanism of omega-3 polyunsaturated fatty acids on intestinal injury in rats with obstructive jaundice.

OBJECTIVE: Obstructive jaundice (OJ) is a common clinical pathological syndrome in hepatobiliary surgery. High incidence of multiple organ injuries during perioperative period and its associated mortality remains challenging in clinical practice. Omega-3 polyunsaturated fatty acids (ω-3 PUFA) is an important enteral immune nutrition. This study investigated the protective role of ω-3 PUFA in the regulation of inflammatory response in OJ. MATERIALS AND METHODS: Seventy-two rats were randomly divided into obstructive jaundice (OJ) group, obstructive jaundice + ω-3 PUFA group (OJPUFA) group, and sham group. OJ model was created by ligation of the bile duct. Abdominal thoracic catheter was placed to collect lymph. Body weight, liver function, serum and lymphatic levels of TNF-α, IL-1ß, IL-10, HMGB1, and nitric oxide (NO) were measured on day 3, day 7, and day 14 after operation. Hematoxylin staining and Alcian blue-periodic acid-Shiff (AB-PAS) staining were performed on the ileum tissue. Protein and mRNA expression of HMGB1, TLR4, and NF-κB p65 were measured at the aforementioned time points. RESULTS: The general condition, including body weight and liver function, were worse in the OJ and the OJPUFA group compared to that in the sham group. On day 14, the body weight recovery and liver function were significantly better in the OJPUFA group than those in the OJ group were (p<0.05 for all). No marked change in the serum and lymphatic levels of TNF-α, IL-1ß, IL-10, HMGB1 and NO was observed in the sham group after operation, while corresponding levels in the OJ and the OJPUFA groups were significantly higher. Compared with the OJPUFA group, serum and lymphatic levels of the above factors were consistently higher in the OJ group and were significantly higher on day 14 (p<0.05 for all). At the same time, ω-3 PUFA lowered the damage of intestinal villi and intestinal mucosal epithelium. It also improved the number and function of goblet cells in intestinal mucosal epithelium. The protein and mRNA expression of HMGB1, TLR4, and NF-κB p65 were significantly higher in the OJ group than those in the OJPUFA group (p<0.05 for all). CONCLUSIONS: ω-3 PUFA has protective effect in the management of obstructive jaundice. It can regulate the inflammatory response and reduce its damage to intestinal structure. Reducing the activation of HMGB1/TLR4/ NF-κB pathway might be a mechanism for its protective effect. We suggested that ω-3 PUFA and drugs targeted HMGB1/TLR4/NF-κB pathway might be potential treatment strategies in obstructive jaundice.

Neuroprotection against ischemic brain injury by a small peptide inhibitor of c-Jun N-terminal kinase (JNK) via nuclear and non-nuclear pathways.

Our previous studies and the others have strongly suggested that c-Jun N-terminal kinase (JNK) signaling pathway plays a critical role in ischemic brain injury. Here we reported that Tat-JNK binding domain (JBD) of JNK-interacting protein-1 (JIP-1), a smaller 11-mer peptide corresponding to residues 153-163 of murine JIP-1 conjugated to Tat peptide, perturbed the assembly of JIP-1-JNK3 complexes, thus inhibiting the activation of JNK3 induced by ischemia/reperfusion in the vulnerable hippocampal CA1 subregion. As a result, Tat-JBD diminished the increased phosphorylation of c-Jun (a nuclear substrate of JNK) and the increased expression of Fas ligand induced by ischemia/reperfusion in the vulnerable hippocampal CA1 subregion. At the same time, through inhibiting phosphorylation of Bcl-2 (a cytosolic target of JNK) and the release of Bax from Bcl-2/Bax dimers, Tat-JBD attenuated Bax translocation to mitochondria and the release of cytochrome c induced by ischemia/reperfusion. Furthermore, the activation of caspase3 and hydrolyzation of poly-ADP-ribose-polymerase induced by brain ischemia/reperfusion were also significantly suppressed by preinfusion of the peptide Tat-JBD. Importantly, Tat-JBD showed neuroprotective effects on ischemic brain damage in vivo, and administration of the peptide after ischemia also achieved the same effects as preinfusion of the peptide did. Thus, our findings imply that Tat-JBD induced neuroprotection against ischemia/reperfusion in rat hippocampal CA1 region via inhibiting nuclear and non-nuclear pathways of JNK signaling. Taken together, these results indicate that Tat-JBD peptide provides a promising therapeutic approach for ischemic brain injury.

Thyroid hormone exacerbates vasoconstriction in insulin resistance: the role of ONOO(-).

Insulin resistance has been proposed to play a pivotal role in vasoconstriction due to increased oxidative stress. Hyperthyroidism would amplify cardiovascular disease risk in diabetic patients, though thyroid hormone advance vascular relaxation and reduce vascular contraction by virtue of NO production in vascular smooth muscle cells (VSMCs). Thus, we aimed to investigate the vascular tone and its underlying mechanism in insulin resistance accompanied by hyperthyroidism. Vascular reactivity studies showed that endothelium-denuded thoracic aortic rings from rats fed with high-fat high-sucrose (HFHS) diet and L-T4 (HFHS+L-T4) exhibited a stronger contractile response to noradrenaline than HFHS rats, which was reversed by L-NAME and GSH. Furthermore, rat thoracic aortic smooth muscle cells (A10) simultaneously stimulated with high glucose insulin (high Glc/Ins) and T3 demonstrated lower NO, superoxide anion ( [Formula: see text] ) levels, and higher iNOS, nitrite ( [Formula: see text] ), peroxynitrite (ONOO(-)) levels than that treated with T3 only. Excessive ONOO(-) markedly aggravated oxidative stress. Thus, we hypothesized that the elevated concentration of ONOO(-) which is generated by NO and [Formula: see text] could be critically instrumental in the progression of vasoconstriction by increasing oxidative stress.

Neuroprotection of ethanol against ischemia/reperfusion-induced brain injury through decreasing c-Jun N-terminal kinase 3 (JNK3) activation by enhancing GABA release.

Our latest study indicated that ethanol could attenuate cerebral ischemia/reperfusion-induced brain injury through activating Ionotropic glutamate receptors Kainate Family (Gluk1)-kainate (KA) receptors and gamma-aminobutyric acid (GABA) receptors. However, the possible mechanism of the neuroprotective effects of ethanol remains unclear. In this study we report that ethanol shows neuroprotective effects against ischemic brain injury through enhancing GABA release and then decreasing c-Jun N-terminal kinase 3 (JNK3) activation. Electrophysiologic recording indicated that ethanol enhances GABA release from presynaptic neurons and the released GABA subsequently inhibits the KA receptor-mediated whole-cell currents. Moreover, our data show that ethanol can inhibit the increased assembly of the Gluk2-PSD-95-MLK3 (postsynaptic density protein-95, PSD-95 and mixed-lineage kinase 3, MLK3) module induced by cerebral ischemia and the activation of the MLK3-MKK4/7-JNK (mitogen-activated protein kinase kinase 4/7, MKK4/7) cascade. Pretreatment of the GABA(A) receptor antagonist bicuculline and antagonist of VGCC (a broad-spectrum blocker of the voltage-gated calcium channel [VGCC]) Chromic (CdCl(2)) can demolish the neuroprotective effects of ethanol. The results suggest that during ischemia-reperfusion, ethanol may activate presynaptic Gluk1-KA and facilitate Ca(2+)-dependent GABA release. The released GABA activates postsynaptic GABA(A) receptors, which suppress the ischemic depolarization and decrease the association of signaling module Gluk2-PSD-95-MLK3 induced by the activation of postsynaptic Gluk2-KA receptors. There is a raised possibility that ethanol inhibiting the JNK3 apoptotic pathway (MLK3/MKK4/7/JNK3/c-Jun/Fas-L) performs a neuroprotective function against ischemic brain injury.