Gene deletion of the kinin receptor B1 attenuates cardiac inflammation and fibrosis during the development of experimental diabetic cardiomyopathy

OBJECTIVE

Diabetic cardiomyopathy is associated with increased mortality in patients with diabetes. The underlying pathology of this disease is still under discussion. We studied the role of the kinin B1 receptor on the development of experimental diabetic cardiomyopathy.

RESEARCH DESIGN AND METHODS

We utilized B1 receptor knockout mice and investigated cardiac inflammation, fibrosis, and oxidative stress after induction of streptozotocin (STZ)-induced diabetes. Furthermore, the left ventricular function was measured by pressure-volume loops after 8 weeks of diabetes.

RESULTS

B1 receptor knockout mice showed an attenuation of diabetic cardiomyopathy with improved systolic and diastolic function in comparison with diabetic control mice. This was associated with a decreased activation state of the mitogen-activated protein kinase p38, less oxidative stress, as well as normalized cardiac inflammation, shown by fewer invading cells and no increase in matrix metalloproteinase-9 as well as the chemokine CXCL-5. Furthermore, the profibrotic connective tissue growth factor was normalized, leading to a reduction in cardiac fibrosis despite severe hyperglycemia in mice lacking the B1 receptor.

CONCLUSIONS

These findings suggest that the B1 receptor is detrimental in diabetic cardiomyopathy in that it mediates inflammatory and fibrotic processes. These insights might have useful implications on future studies utilizing B1 receptor antagonists for treatment of human diabetic cardiomyopathy.

Doxorubicin cardiomyopathy-induced inflammation and apoptosis are attenuated by gene deletion of the kinin B1 receptor

Clinical use of the anthracycline doxorubicin (DOX) is limited by its cardiotoxic effects, which are attributed to the induction of apoptosis. To elucidate the possible role of the kinin B1 receptor (B1R) during the development of DOX cardiomyopathy, we studied B1R knockout mice (B1R(-/-)) by investigating cardiac inflammation and apoptosis after induction of DOX-induced cardiomyopathy. DOX control mice showed cardiac dysfunction measured by pressure-volume loops in vivo. This was associated with a reduced activation state of AKT, as well as an increased bax/bcl2 ratio in Western blots, indicating cardiac apoptosis. Furthermore, mRNA levels of the proinflammatory cytokine interleukin 6 were increased in the cardiac tissue. In DOX B1R(-/-) mice, cardiac dysfunction was improved compared to DOX control mice, which was associated with normalization of the bax/bcl-2 ratio and interleukin 6, as well as AKT activation state. These findings suggest that B1R is detrimental in DOX cardiomyopathy in that it mediates the inflammatory response and apoptosis. These insights might have useful implications for future studies utilizing B1R antagonists for treatment of human DOX cardiomyopathy.

Toll-like receptor-4 modulates survival by induction of left ventricular remodeling after myocardial infarction in mice

Left ventricular (LV) remodeling is known to contribute to morbidity and mortality after myocardial infarction (MI). Because LV remodeling is strongly associated with an inflammatory response, we investigated whether or not TLR-4 influences LV remodeling and survival in a mice model of MI. Six days after MI induction, TLR4 knockout (KO)-MI mice showed improved LV function 32 and reduced LV remodeling as indexed by reduced levels of atrial natriuretic factor and total collagen as well as by a reduced heart weight to body weight ratio when compared with WT-MI mice. This was associated with a reduction of protein levels of the intracellular TLR4 adapter protein MyD88 and enhanced protein expression of the anti-hypertrophic JNK in KO-MI mice when compared with wild-type (WT)-MI mice. In contrast, protein activation of the pro-hypertrophic kinases protein kinase Cdelta and p42/44 were not regulated in KO-MI mice when compared with WT-MI mice. Improved LV function, reduced cardiac remodeling, and suppressed intracellular TLR4 signaling in KO-MI mice were associated with significantly improved survival compared with WT-MI mice (62 vs 23%; p < 0.0001). TLR4 deficiency led to improved survival after MI mediated by attenuated left ventricular remodeling.

Low-dose treatment with atorvastatin leads to anti-oxidative and anti-inflammatory effects in diabetes mellitus

We investigated whether atorvastatin, given in a dose to low to influence the lipid profile, has any effect on oxidative stress, inflammation and endothelial function under streptozotocin-induced diabetic conditions. Diabetes mellitus was induced in male Sprague Dawley rats by a single injection of streptozotocin. Rats were treated chronically with atorvastatin (50 mg/kg/day; p.o.) or vehicle until day 48 and compared with controls. NAD(P)H activity, protein expression nuclear factor-kappaBp65 (NF-kappaBp65) and phosphorylation of the extracellular signal-regulated kinase (ERK1/2) were assessed in the quadriceps muscle. Protein and mRNA levels of intracellular and vascular adhesion molecules (ICAM-1, VCAM-1) and cytokines were measured by Taqman or immunohistochemistry staining, respectively. Endothelial function was investigated in vivo using the autoperfused hind limb model. Diabetic groups displayed similar severe hyperglycemia. Untreated diabetic rats showed enhanced NAD(P)H activity, activation of the ERK1/2/NF-kappaBp65-pathway, enhanced expression of cytokines and cellular adhesion molecules and impaired vascular function. Low-dose therapy by atorvastatin did not alter the lipid profile but led to a reduction of NAD(P)H activity (-28%, P<0.05) associated with reduced protein expression of NF-kappaBp65 (-53%, P<0.05) and phosphorylation of its regulator mitogen-activated protein kinase (MAPK) ERK1/2 in diabetic rats. Also inflammatory markers were reduced after atorvastatin treatment indexed by reduced mRNA expression of VCAM-1 (-24%), tumor necrosis factor alpha (-59%) and interleukin 1beta (-50%) and reduced ICAM-1 (-81%) and VCAM-1 (-74%) positive staining. These beneficial effects were associated with improved endothelium-dependent vasodilatation (maximal vasodilatation: +101%; P<0.05). Lipid-independent anti-oxidative and anti-inflammatory effects of low-dose atorvastatin involving the ERK1/2/NF-kappaB-pathway are sufficient to improve endothelial function under experimental diabetic conditions.

Chronic inhibition of p38MAPK improves cardiac and endothelial function in experimental diabetes mellitus

To investigate the influence of p38 mitogen activated kinase (p38MAPK) on the development of diabetic cardiac and endothelial dysfunction, we assessed left ventricular and vascular function as well as inflammatory markers in diabetic rats after chronic pharmacological inhibition of p38MAPK. Diabetes mellitus was induced in rats by a single injection of streptozotocin. Rats were treated with the p38MAPK inhibitor SB 239063 (40 mg/kg/day, p.o.) or vehicle. 48 days after diabetes mellitus-induction, left ventricular function and vascular function were assessed in vivo by TIP-catheter and the autoperfused hindlimb, respectively. Cell adhesion molecules staining was quantified immunohistochemically in the heart and quadriceps muscle, respectively, as well as cardiac phosphorylation of p38MAPK by Western blot analysis. Treated and untreated diabetic groups displayed similar severe hyperglycemia. Left ventricular and endothelial function were impaired in the untreated diabetic group compared to controls (dp/dtmax: -40%, dp/dtmin: +49%, maximal vasodilatation: -57%; P < 0.05) associated with significantly increased cardiac (3-fold) and peripheral cell adhesion molecules staining, respectively. Treatment of diabetic rats with SB 239063 led to a significant reduction of diabetes-induced enhancement of p38MAPK phosphorylation associated with improved left ventricular function (dp/dtmax: +39%, dp/dtmin: +47%; P < 0.05) and peripheral endothelial function (maximal vasodilatation: +71%; P < 0.05) under diabetic conditions. This was associated with reduced cardiac and peripheral inflammation indexed by reduced adhesion molecules content. Pharmacological inhibition of p38MAPK is sufficient to mitigate the development of diabetic cardiac and endothelial dysfunction despite of hyperglycemia. Our data suggest that the anti-inflammatory properties due to p38MAPK inhibition contribute to these beneficial cardiovascular effects.

Inhibition of p38 mitogen-activated protein kinase attenuates left ventricular dysfunction by mediating pro-inflammatory cardiac cytokine levels in a mouse model of diabetes mellitus

AIMS/HYPOTHESIS

We investigated the effect of SB 203580, a pharmacological inhibitor of p38 mitogen-activated protein kinase (MAPK), on cardiac inflammation, cardiac fibrosis, and left ventricular function using an animal model of diabetic cardiomyopathy.

MATERIALS AND METHODS

Diabetes mellitus was induced by streptozotocin (50 mg/kg i.p. for 5 days) in 20 C57/BL6J mice. Diabetic mice were treated daily with the p38 MAPK inhibitor SB 203580 (1 mg/kg daily, n=10) or with placebo (n=10) and were compared to non-diabetic controls. Left ventricular function was measured by pressure-volume loops after 8 weeks of diabetes mellitus. The parameters for systolic function were the end systolic pressure-volume relationship (ESPVR) and the left ventricular end systolic pressure. The parameters for diastolic function were the left ventricular end diastolic pressure and the end diastolic pressure-volume relationship (EDPVR). Cardiac tissue was analysed by ELISA for the protein content of the cytokines TNF-alpha, IL6, IL1-beta, and TGF-beta1. Phosphorylation of MAPK p38 was analysed by western blot, and the total cardiac collagen content was analysed by Sirius red staining.

RESULTS

Left ventricular dysfunction was documented by impaired ESPVR and EDPVR. Cardiac cytokine levels and cardiac fibrosis were increased in diabetic animals compared to controls. Treatment with the p38 inhibitor normalised cardiac cytokine levels and improved systolic function, but did not change cardiac fibrosis and diastolic dysfunction compared to placebo.

CONCLUSIONS/INTERPRETATION

Pharmacological inhibition of p38 MAPK prevents cardiac inflammation and attenuates left ventricular dysfunction in diabetic cardiomyopathy.

[Effect of various combinations of DL-alpha-tocopherol and acetylsalicylic acid on adjuvant arthritis in the rat]

The influence of per os application of different combinations of DL-alpha-tocopherol (TOC) and acetylsalicylic acid (ASS) on adjuvant-induced arthritis was tested in male Wistar rats (body weight 227 +/- 18 g; 8 groups, n = 8). One group (control) was without adjuvans arthritis and received no treatment, another group was also not treated in spite of adjuvans arthritis. Further, six groups of adjuvans arthritis were treated with the following combinations: ASS/TOC (mg/kg BW/d each) 250/-, 250/250, 167/250, 83/250, 167/167 and 167/83. During the course of the experiment (21 d), body weights, food intake, and the swelling of injected and noninjected paws, and (at the end of the test period) relative weight of spleen and the albumin-globulin-ratio in plasma were recorded. With the ASS/TOC combination of 250 mg/kg BW each, the highest antiinflammatory effect could be reached, as compared with all treated groups. The reduction of acetylsalicylic acid does by one-third to 167 mg/kg BW in combination with 250 mg DL-alpha-tocopherol/kg BW seem to have the same antiphlogistic effect as acetylsalicylic acid alone at 250 mg/kg BW. This positive effect could be confirmed by the partially normalized relative spleen weight and albumin-globulin-ratio. The results allow the conclusion: --main antiphologistic effect of the combination is due to acetylsalicylic acid; --when combined with 250 mg DL-alpha-tocopherol/kg BW acetylsalicylic acid dosage can be reduced by one-third to 167 mg/kg BW and still have the same effect as ASS alone (250 mg/kg BW); --further reductions of ASS and/or DL-alpha-tocopherol dosage minimize the antiinflammatory effect.

[Effect of vitamin E on experimental inflammation in rats]

Besides other mediators like prostaglandins, kinins and histamine, oxygen radicals potentiate inflammations. Vitamin E as natural antioxidant could scavenge radicals produced during an inflammation and therefore reduce the inflammatory response. In experiments with male Wistar rats maintained on a diet deficient in or supplemented with vitamin E for 6 weeks the influence of the administration of DL-alpha-tocopherol on the inflammation of the right hind paw was tested. The irritation produced by injection of Freund's complete adjuvants was observed for 21 days. Measuring the thickness of the paw and the activity of acid phosphatase in the paw tissue there was no difference in the intensity of inflammation among the control and the vitamin-E-deficient diet groups. The supplementation with a pharmacological dose of tocopherol (324 mg DL-alpha-tocopherol/100 g food) had no effect on the inflammation of animals with different vitamin E supplements. Differences in the antioxidant status (contents of tocopherol and malondialdehyde in several organs, activity of creatine kinase in plasma) among the groups were mainly linked to the various tocopherol supplies. The irritation increased the lipid peroxidation in liver mitochondria and the activity of creatine kinase in the plasma. The data show no influence of vitamin E on this kind of inflammation.