Interaction between tumor necrosis factor-alpha and leptin-induced inhibition of cardiac contractile function in isolated ventricular myocytes

Adipokines and the cardiovascular system: mechanisms mediating health and disease

This review focuses on the role of adipokines in the maintenance of a healthy cardiovascular system, and the mechanisms by which these factors mediate the development of cardiovascular disease in obesity. Adipocytes are the major cell type comprising the adipose tissue. These cells secrete numerous factors, termed adipokines, into the blood, including adiponectin, leptin, resistin, chemerin, omentin, vaspin, and visfatin. Adipose tissue is a highly vascularised endocrine organ, and different adipose depots have distinct adipokine secretion profiles, which are altered with obesity. The ability of many adipokines to stimulate angiogenesis is crucial for adipose tissue expansion; however, excessive blood vessel growth is deleterious. As well, some adipokines induce inflammation, which promotes cardiovascular disease progression. We discuss how these 7 aforementioned adipokines act upon the various cardiovascular cell types (endothelial progenitor cells, endothelial cells, vascular smooth muscle cells, pericytes, cardiomyocytes, and cardiac fibroblasts), the direct effects of these actions, and their overall impact on the cardiovascular system. These were chosen, as these adipokines are secreted predominantly from adipocytes and have known effects on cardiovascular cells.

Aging linked to type 2 diabetes increases oxidative stress and chronic inflammation

Oxidative stress (OxS) and inflammation are physiopathological mechanisms related to diabetes and aging. We evaluated the additive effect of diabetes and aging on OxS and inflammation in a cross-sectional comparative study of 228 subjects: (1) 56 healthy adults (mean age, 47 ± 7 years); (2) 60 diabetic adults (mean age, 52 ± 6 years); (3) 40 healthy elderly adults (mean age, 67 ± 7 years); and (4) 72 diabetic elderly adults (mean age, 68 ± 7 years). We measured levels of glycosylated hemoglobin (HbA1c), plasma lipid peroxides, superoxide dismutase, glutathione peroxidase, total antioxidants, and tumor necrosis factor-alpha (TNF-α). The results indicate that diabetes is a risk factor for subjects with high serum levels of TNF-α (odds ratio [OR] = 12.1; 95% confidence interval [95% CI], 5.0-28; p < 0.001); this correlation becomes stronger when it is also associated with aging (OR = 14; 95% CI, 3.7-53.7; p < 0.05). Likewise, we observed that diabetes is an independent risk factor for OxS (OR = 2.1; 95% CI, 1.2-3.8; p < 0.05), and a stronger factor in older patients (OR = 3.1; 95% CI, 1.3-7.5; p < 0.05). Our findings suggest that aging, in concert with diabetes, exerts an additive effect on OxS and inflammation.

Mechanisms of TNFalpha-induced cardiac dysfunction in cholestatic bile duct-ligated mice: interaction between TNFalpha and endocannabinoids

BACKGROUND & AIMS

Chronic liver disease is associated with endotoxemia, oxidative stress, increased endocannabinoids and decreased cardiac responsiveness. Endocannabinoids activate the tumor necrosis factor-alpha (TNFalpha)-nuclear factor kappaB (NFkappaB) pathway. However, how they interact with each other remains obscure. We therefore aimed to clarify the relationship between the TNFalpha-NFkappaB pathway and endocannabinoids in the pathogenesis of cardiodepression of cholestatic bile duct ligated (BDL) mice.

METHODS

BDL mice with TNFalpha knockout (TNFalpha-/-) and infusion of anti-TNFalpha antibody were used. Cardiac mRNA and protein expression of NFkappaBp65, c-Jun-N-terminal kinases (JNK), p38 mitogen-activated protein kinase (p38MAPK), extracelullar-signal- regulated kinase (ERK), inducible nitric oxide synthase (iNOS), Copper/Zinc and Magnesium-superoxide dismutase (Cu/ Zn- and Mn-SOD), cardiac anandamide, 2-arachidonoylglycerol (2-AG), nitric oxide (NOx) and glutathione, and plasma TNFalpha were measured. The effects of TNFalpha, cannabinoid receptor (CB1) antagonist AM251 and the endocannabinoid reuptake inhibitor UCM707, on the contractility of isolated cardiomyocytes, were assessed.

RESULTS

In BDL mice, cardiac mRNA and protein expression of NFkappaBp65, p38MAPK, iNOS, NOx, anandamide, and plasma TNFa were increased, whereas glutathione, Cu/Zn-SOD, and Mn-SOD were decreased. Cardiac contractility was blunted in BDL mice. Anti-TNFa treatment in BDL mice decreased cardiac anandamide and NOx, reduced expression of NFkappaBp65, p38MAPK, and iNOS, enhanced expression of Cu/Zn-SOD and Mn-SOD, increased reductive glutathione and restored cardiomyocyte contractility. TNFa-depressed contractility was worsened by UCM707, whereas AM251 improved contractility.

CONCLUSIONS

Increased TNFalpha, acting via NFkappaB-iNOS and p38MAPK signaling pathways, plays an important role in the pathogenesis of cardiodepression in BDL mice. TNFalpha also suppressed contractility by increasing oxidative stress and endocannabinoid activity.

Leptin signaling and obesity: cardiovascular consequences

Leptin, among the best known hormone markers for obesity, exerts pleiotropic actions on multiple organ systems. In this review, we summarize major leptin signaling pathways, namely Janus-activated kinase/signal transducers and activators of transcription and mitogen-activated protein kinase, including possible mechanisms of leptin resistance in obesity. The effects of leptin on the cardiovascular system are discussed in detail, including its contributions to hypertension, atherosclerosis, depressed myocardial contractile function, fatty acid metabolism, hypertrophic remodeling, and reduction of ischemic/reperfusion injury. The overall goal is to summarize current understanding of how altered leptin signaling in obesity contributes to obesity-related cardiovascular disease.

Allograft inflammatory factor-1 and its immune regulation

The allograft inflammatory factor-1 (AIF-1) is a 17 kDa interferon-gamma (IFN-gamma) inducible Ca(2+)-binding EF-hand protein that is encoded within the HLA class III genomic region. Three proteins including ionized Ca(2+)-binding adaptor 1, microglia response factor-1, and daintain are identical with AIF-1. The expression of AIF-1 was mostly limited to the monocyte/macrophage lineage, and augmented by cytokines such as IFN-gamma. It was assumed that AIF-1 was a novel molecule involved in inflammatory responses, allograft rejection, as well as the activation and function of macrophages. However, it has been reported that AIF-1 is also expressed in macrophages and microglial cells in autoimmune diseases such as experimental autoimmune encephalomyelitis, neuritis and uveitis models, suggesting that AIF-1 may play a pivotal role in autoimmunity. In the present manuscript, the genomic and functional characteristics of AIF-1 family proteins as well as their immune regulatory effects are reviewed.

Improvement of chronic heart failure by dexamethasone is not associated with downregulation of leptin in rats

AIM

To demonstrate the hypothesis that dexamethasone (Dex) could improve chronic heart failure (CHF) by inhibiting the downstream signaling transduction of leptin but had no influence on the upregulation of leptin and its receptor in myocardium.

METHODS

CHF was induced by left coronary artery ligation for 6 weeks. CHF rats were treated with Dex 50 mg.kg/d. Hemodynamics, histology, reactive oxygen species (ROS)-related parameters, and leptin concentrations in serum were measured. The mRNA expression of matrix metalloproteinases (MMP)2/9, tissue inhibitor of metalloproteinases (TIMP)1/2, tumor necrosis factor (TNF)-alpha, and OB-Rb were measured by RT-PCR.

RESULTS

In the CHF rats, hemodynamic functions were deteriorated, which was accompanied with myocardium remodeling and histological changes. CHF rats showed hyperleptinemia and excessive ROS in the serum, and the upregulation of MMP-2/9, TNF-alpha, and leptin receptor mRNA and downregulation of TIMP-1/2 mRNA in the myocardium compared with the sham operation group. Dex treatment significantly ameliorated CHF in association with the reversion of the abnormalities of MMP-2/9, TIMP-1/2, TNF-alpha, and ROS. But Dex had no influence on the hyperleptinemia and the upregulated leptin and its receptor in the myocardium during CHF.

CONCLUSION

Dex improves CHF by inhibiting TNF-alpha, MMP-2, MMP-9, and ROS. Dex had no effects on upregulated leptin and its receptor expression and hyperleptinemia induced by CHF.