High glucose enhances inducible nitric oxide synthase expression. Role of protein kinase C-betaII

Leucoglycemic index predicts post-operative vasopressor-inotropic requirement after adult cardiac surgery (LEUCOGLYPTICS): A retrospective single-center study

Background and Aims

Cardiac surgery often necessitates considerable post-operative vasoactive-inotropic support. Given an encouraging literature on the prognostic potential of leucoglycemic index (LGI) [serum glucose (mg/dl) × total leucocytes count (cells/mm3)/1000], we aimed to evaluate whether intensive care unit (ICU)-admission LGI can predict post-operative vasopressor-inotropic requirements following cardiac surgery on cardio-pulmonary bypass (CPB).

Material and Methods

The data of patients undergoing cardiac surgery at our tertiary care center between January 2015 and December 2020 was retrospectively reviewed. The vasopressor-inotropic requirement was estimated using the VIS (vasoactive-inotropic score) values over the first post-operative 72 hrs. Subsequently, VISi (indexed VIS) was computed as maxVIS[0-24hrs] + maxVIS[24-48hrs] +2 × maxVIS[48-72hrs]/10), and the study participants were divided into h-VISi (VISi ≥3) and l-VISi (VISi <3).

Results

Out of 2138 patients, 479 (22.40%) patients categorized as h-VISi. On univariate analysis: LGI, age, European System for Cardiac Operative Risk Evaluation score (EuroSCORE II), left-ventricle ejection fraction, prior congestive heart failure (CHF), chronic renal failure, angiotensin-converting enzyme inhibitors, combined surgeries, CPB and aortic cross-clamp (ACC) duration, blood transfusion, and immediate post-operative glucose were significant h-VISi predictors. Subsequent to multi-variate analysis, the predictive performance of LGI (OR: 1.09; 95% CI: 1.03-1.14; P = 0.002) prior CHF (OR: 2.35; 95% CI: 1.44-3.82; P = 0.001), CPB time (OR: 1.08; 95% CI: 1.02-1.14; P = 0.019), ACC time (OR: 1.03; 95% CI: 1.02-1.04; P = 0.008), and EuroSCORE II (OR: 1.14; 95% CI: 1.06-1.21; P < 0.001) remained significant. With 1484.75 emerging as the h-VISi predictive cut-off, patients with LGI ≥ 1484.75 also had a higher incidence of vasoplegia, low-cardiac output syndrome, new-onset atrial fibrillation, acute kidney injury, and mortality. LGI additionally exhibited a significant positive correlation with duration of mechanical ventilation and ICU stay (R = 0.495 and 0.564, P value < 0.001).

Conclusion

An elevated LGI of greater than 1484.75 independently predicted a VISindex ≥3 following adult cardiac surgery on CPB.

Metformin Induces Oxidative Stress-Mediated Apoptosis without the Blockade of Glycolysis in H4IIE Hepatocellular Carcinoma Cells

Metformin, a widely prescribed anti-diabetic drug, also exerts anti-cancer effects in different types of cancers. Although a number of molecular mechanisms have been suggested, the metabolic features underlying metformin's anti-cancer activity is not fully understood enough. Because cancer cells have been known to prefer inefficient aerobic glycolysis to support their proliferation, it is important to clarify by which metformin affects metabolism to suppress the proliferation of cancer cells. Here, we report the metabolic changes induced by metformin and its relevance to the induction of apoptosis in H4II rat hepatocellular carcinoma cells. H4IIE cells were treated with metformin and other reagents in culture media with various nutritional compositions. Glutamine as well as pyruvate enhanced the viability of H4IIE cells in glucose-deprived conditions. Protective effects of glucose and pyruvate were comparable at same concentrations (5 mM). Metformin induced apoptosis irrespective of any nutritional conditions. Glucose consumption and lactate production were stimulated by metformin. Inhibition of glycolysis by 2-deoxyglucose suppressed the metformin-induced lactate production but additively enhanced metformin's pro-apoptotic effect. These results indicate that metformin does not interfere but accelerate glycolysis. Unexpectedly, the production of reactive oxygen species (ROS) was markedly stimulated by metformin. A potent antioxidant, N-acetylcysteine (NAC) suppressed all pro-apoptotic changes as well as ROS generation induced by metformin. Taken together, metformin does not interfere with glycolysis but promotes apoptosis by enhancing oxidative stress.

Double antioxidant activities of rosiglitazone against high glucose-induced oxidative stress in hepatocyte

Chronic hyperglycemia is the hallmark of diabetes and its complication. High glucose-induced excessive reactive oxygen species (ROS) production has been considered to play an important role in the development of diabetes. However, the influence of high glucose on the liver remains to be clarified. Rosiglitazone (RSG) is a member of thiazolidinediones (TDZs) family, which is the ligand of the of nuclear transcription factor peroxisome proliferator-activated receptor-γ (PPARγ), being used clinically for the treatment of type 2 diabetic patients through their insulin-sensitizing effect. In the present study, we investigated the cytotoxicity of high glucose in QZG hepatocytes and evaluated the protective effect of RSG. The results showed that high glucose significantly reduced cell viability through generation of ROS via activation of PKC, which was inhibited by RSG. On the one hand, RSG notably inhibited the activation of PKC induced by high glucose independent of PPARγ, leading to the decrease of ROS generation. On the other hand, RSG notably increased the expression of key antioxidant transcription factor Nrf2 and antioxidant enzyme HO-1 in a PPARγ-dependent manner, leading to the elimination of excessive ROS. In addition, RSG also inhibited the decrease of COX-2 expression induced by high glucose through activating PPARγ. Furthermore, the activation of Akt and MAPKs was involved in the effect of RSG on Nrf2, HO-1 and COX-2. In summary, our study supports the hypothesis that RSG protect hepatocytes from high glucose-induced toxicity through PPARγ-dependent and PPARγ-independent pathways.

Vascular hyporesponsiveness to vasopressors in septic shock: from bench to bedside

PURPOSE

To delineate some of the characteristics of septic vascular hypotension, to assess the most commonly cited and reported underlying mechanisms of vascular hyporesponsiveness to vasoconstrictors in sepsis, and to briefly outline current therapeutic strategies and possible future approaches.

METHODS

Source data were obtained from a PubMed search of the medical literature with the following MeSH terms: Muscle, smooth, vascular/physiopathology; hypotension/etiology; shock/physiopathology; vasodilation/physiology; shock/therapy; vasoconstrictor agents.

RESULTS

Nitric oxide (NO) and peroxynitrite are crucial components implicated in vasoplegia and vascular hyporeactivity. Vascular ATP-sensitive and calcium-activated potassium channels are activated during shock and participate in hypotension. In addition, shock state is characterized by inappropriately low plasma glucocorticoid and vasopressin concentrations, a dysfunction and desensitization of alpha-receptors, and an inactivation of catecholamines by oxidation. Numerous other mechanisms have been individualized in animal models, the great majority of which involve NO: MEK1/2-ERK1/2 pathway, H(2)S, hyperglycemia, and cytoskeleton dysregulation associated with decreased actin expression.

CONCLUSIONS

Many therapeutic approaches have proven their efficiency in animal models, especially therapies directed against one particular compound, but have otherwise failed when used in human shock. Nevertheless, high doses of catecholamines, vasopressin and terlipressin, hydrocortisone, activated protein C, and non-specific shock treatment have demonstrated a partial efficiency in reversing sepsis-induced hypotension.

Selective inhibition of protein kinase C beta(2) attenuates inducible nitric oxide synthase-mediated cardiovascular abnormalities in streptozotocin-induced diabetic rats

OBJECTIVE

Impaired cardiovascular function in diabetes is partially attributed to pathological overexpression of inducible nitric oxide synthase (iNOS) in cardiovascular tissues. We examined whether the hyperglycemia-induced increased expression of iNOS is protein kinase C-beta(2) (PKCbeta(2)) dependent and whether selective inhibition of PKCbeta reduces iNOS expression and corrects abnormal hemodynamic function in streptozotocin (STZ)-induced diabetic rats.

RESEARCH DESIGN AND METHODS

Cardiomyocytes and aortic vascular smooth muscle cells (VSMC) from nondiabetic rats were cultured in low (5.5 mmol/l) or high (25 mmol/l) glucose or mannitol (19.5 mmol/l mannitol + 5.5 mmol/l glucose) conditions in the presence of a selective PKCbeta inhibitor, LY333531 (20 nmol/l). Further, the in vivo effects of PKCbeta inhibition on iNOS-mediated cardiovascular abnormalities were tested in STZ-induced diabetic rats.

RESULTS

Exposure of cardiomyocytes to high glucose activated PKCbeta(2) and increased iNOS expression that was prevented by LY333531. Similarly, treatment of VSMC with LY333531 prevented high glucose-induced activation of nuclear factor kappaB, extracellular signal-related kinase, and iNOS overexpression. Suppression of PKCbeta(2) expression by small interference RNA decreased high-glucose-induced nuclear factor kappaB and extracellular signal-related kinase activation and iNOS expression in VSMC. Administration of LY333531 (1 mg/kg/day) decreased iNOS expression and formation of peroxynitrite in the heart and superior mesenteric arteries and corrected the cardiovascular abnormalities in STZ-induced diabetic rats, an action that was also observed with a selective iNOS inhibitor, L-NIL.

CONCLUSIONS

Collectively, these results suggest that inhibition of PKCbeta(2) may be a useful approach for correcting abnormal hemodynamics in diabetes by preventing iNOS mediated nitrosative stress.

Aging-associated dysfunction of Akt/protein kinase B: S-nitrosylation and acetaminophen intervention

Background

Aged skeletal muscle is characterized by an increased incidence of metabolic and functional disorders, which if allowed to proceed unchecked can lead to increased morbidity and mortality. The mechanism(s) underlying the development of these disorders in aging skeletal muscle are not well understood. Protein kinase B (Akt/PKB) is an important regulator of cellular metabolism and survival, but it is unclear if aged muscle exhibits alterations in Akt function. Here we report a novel dysfunction of Akt in aging muscle, which may relate to S-nitrosylation and can be prevented by acetaminophen intervention.

Principal Findings

Compared to 6- and 27-month rats, the phosphorylation of Akt (Ser473 and Thr308) was higher in soleus muscles of very aged rats (33-months). Paradoxically, these increases in Akt phosphorylation were associated with diminished mammalian target of rapamycin (mTOR) phosphorylation, along with decreased levels of insulin receptor beta (IR-β), phosphoinositide 3-kinase (PI3K), phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and phosphorylation of phosphoinositide-dependent kinase-1 (PDK1) (Ser241). In vitro Akt kinase measurements and ex vivo muscle incubation experiments demonstrated age-related impairments of Akt kinase activity, which were associated with increases in Akt S-nitrosylation and inducible nitric oxide synthase (iNOS). Impairments in Akt function occurred parallel to increases in myocyte apoptosis and decreases in myocyte size and the expression of myosin and actin. These age-related disorders were attenuated by treating aged (27-month) animals with acetaminophen (30 mg/kg body weight/day) for 6-months.

Conclusions

These data demonstrate that Akt dysfunction and increased S-nitrosylation of Akt may contribute to age-associated disorders in skeletal muscle and that acetaminophen may be efficacious for the treatment of age-related muscle dysfunction.

Role of protein kinase C β2 activation in TNF-α-induced human vascular endothelial cell apoptosis

The circulatory inflammatory cytokine tumor necrosis factor alpha (TNF-α) is increased in pathologic conditions that initiate or exacerbate vascular endothelial injury, such as diabetes. Protein kinase C (PKC) has been shown to play a critical role in TNF-α-induced human endothelial cell apoptosis. However, the relative roles played by specific isoforms of PKC in TNF-α-induced human endothelial cell apoptosis have not been addressed. We investigated the effects of a selective PKCβ2 inhibitor (CGP53353) on TNF-α-induced apoptosis in human vascular endothelial cells (cell line ECV304) and on the production of reactive oxygen species and nitric oxide, and compared its effects with rottlerin, a reagent that has been shown to reduce PKCδ protein levels. Cultured human vascular endothelial cells (ECV304) were treated for 24 h with one of 4 regimes: 40 ng/mL TNF-α alone (TNF-α), TNF-α with 10 µmol/L rottlerin (T+rottlerin), TNF-α with 1 µmol/L CGP53353 (T+CGP), or untreated (control). Cell viability was measured by MTT assay, and cell apoptosis was assessed by flow cytometry. TNF-α-induced endothelial cell apoptosis was associated with dramatic increases in production of intracellular hydrogen peroxide (approximately 20 times greater than control) and superoxide (approximately 16 times greater than control), as measured by dichlorofluorescein and dihydroethidium fluorescent staining, respectively. This increase was accompanied by reduced activity of superoxide dismutase and glutathione peroxidase and, subsequently, an increase in the lipid peroxidation product malondialdehyde. CGP53353, but not rottlerin, abolished or attenuated all these changes. We conclude that PKCβ2 plays a major role in TNF-α-induced human vascular endothelial cell apoptosis.

Epidemic inflammation: pondering obesity

Over the past two decades, inflammation has been recognized as a major driver in the pathogenesis of several common diseases, including atherosclerosis, diabetes, cancer, and asthma. Over the same period, there has been a steep rise in the incidence of obesity, a major risk factor for these disorders. Inflammation of adipose tissue is now recognized to accompany obesity and contribute to its sequelae. Thus, whereas obesity is primarily a disorder of energy balance, it may be helpful to consider it also as a form of epidemic inflammation that predisposes to other forms of epidemic inflammation. It is a fundamental biologic challenge to understand how a positive energy balance and inflammation are linked. This work reviews evidence that reactive oxygen and nitrogen intermediates (ROI and RNI) help drive chronic inflammation in the obese. This is proposed to be a maladaptive instance of our evolved dependence on ROI and RNI for both homeostatic signaling and host defense. ROI and RNI are well suited for these seemingly contradictory dual functions by their metabolic origin, high diffusibility in water and lipid, atomic specificity, and large number of molecular targets. When we eat so much and work so little that we repeatedly generate reactive compounds at levels normally reserved for emergencies, we treat our own cells like invading microbes.

Increased induction of inducible nitric oxide synthase expression in aortae of type 2 diabetes rats

The aim of this study was to determine whether the pathway of inducible NO synthase (iNOS) in blood vessels is changed by type 2 diabetes. Lipopolysaccharide (LPS)-induced nitric oxide (NO) production and expression of iNOS and effects of LPS on phenylephrine-induced contractile force were compared in aortae isolated from Goto-Kakizaki (G-K) diabetes rats and aortae isolated from control Wistar rats. Both LPS-stimulated nitrite generation and iNOS expression levels were significantly higher in aortae from G-K rats than in those from control rats. Phenylephrine-induced contractile force in the presence of LPS was significantly lower in aortae from G-K rats than in those from control rats, while contractile force in the absence of LPS was comparable in the diabetic and control groups. On the other hand, incubation of aortae in high glucose-containing medium did not affect the LPS-stimulated nitrite accumulation and iNOS expression and the phenylephrine-induced contractile force, regardless of the presence of LPS. These results suggest that LPS-induced NO production through the iNOS pathway is increased and subsequent attenuation of contractile force by excess NO is enhanced in arteries of rats with type 2 diabetes.