Moderate exercise attenuates caspase-3 activity, oxidative stress, and inhibits progression of diabetic renal disease in db/db mice

Diabetic nephropathy, the leading cause of end-stage renal disease, is characterized by a proapoptotic and prooxidative environment. The mechanisms by which lifestyle interventions, such as exercise, benefit diabetic nephropathy are unknown. We hypothesized that exercise inhibits early diabetic nephropathy via attenuation of the mitochondrial apoptotic pathway and oxidative damage. Type 2 diabetic db/db and normoglycemic wild-type mice were exercised for an hour everyday at a moderate intensity for 7 wk, following which renal function, morphology, apoptotic signaling, and oxidative stress were evaluated. Exercise reduced body weight, albuminuria, and pathological glomerular expansion in db/db mice independent of hyperglycemic status. Changes in renal morphology were also related to reduced caspase-3 (main effector caspase in renal apoptosis), caspase-8 (main initiator caspase of the "extrinsic" pathway) activities, and TNF-alpha expression. A role for the mitochondrial apoptotic pathway was unlikely as both caspase-9 activity (initiator caspase of this pathway) and expression of regulatory proteins such as Bax and Bcl-2 were unchanged. Kidneys from db/db mice also produced higher levels of superoxides and had greater oxidative damage concurrent with downregulation of superoxide dismutase (SOD) 1 and 3. Interestingly, although exercise also increased superoxides, there was also upregulation of multiple SODs that likely inhibited lipid (hydroperoxides) and protein (carbonyls and nitrotyrosine) oxidation in db/db kidneys. In conclusion, exercise can inhibit progression of early diabetic nephropathy independent of hyperglycemia. Reductions in caspase-3 and caspase-8 activities, with parallel improvements in SOD expression and reduced oxidative damage, could underlie the beneficial effects of exercise in diabetic kidney disease.

Long-term effect of enhanced external counterpulsation on endothelial function in the patients with intractable angina

BACKGROUND

Enhanced external counterpulsation (EECP) is a noninvasive, pneumatic technique that provides favourable effects in patients with coronary artery disease. The objective of this study was to describe the long-term effect of EECP on endothelial function in patients with ischaemic cardiomyopathy.

METHOD

The study was performed in 15 patients with ischaemic cardiomyopathy. All subjects were treated with EECP 1-h per day, 5 days a week, over 7 weeks (totally 35h). Endothelium-dependent and -independent relaxation was assessed by flow-mediated dilation (FMD) and nitroglycerine-mediated dilatation (NMD). In each patient, FMD and NMD measurements were performed before, at midcourse (day 17th) and after completion of EECP course (day 35th). In addition, FMD index was assessed 1 month after completion of EECP therapy.

RESULTS

Results showed that EECP was associated with a significant improvement in FMD index after 35 hours of EECP (10.95+/-4.1% vs. 7.40+/-4.9% for baseline, p<0.05). NMD index didn't significantly alter during the EECP therapy. Also, 1 month after completion of EECP, FMD index returned to baseline (7.51+/-4.4% vs. 7.40+/-4.9%, respectively, p<0.05). EECP acutely improved endothelial function in ischaemic cardiomyopathic patients. However, after 1 month completion of treatment, endothelium-dependent vasorelaxation returned to baseline.

CONCLUSION

It seems that improvement of endothelial function is not the main mechanism of long-term EECP treatment and other mechanisms should be considered.

Oestrogen promotes coronary angiogenesis even under normoxic conditions

Angiogenic therapy is one of the new treatments of ischaemic heart disease. Oestrogen has angiogenic properties under hypoxic condition, and if oestrogen also induces angiogenesis under normoxic condition, it could be used in combination with other angiogenic therapies in the treatment of ischaemic heart disease. In this study, we evaluated the angiogenic effect of high-dose oestrogen treatment in normoxic rat heart tissue. Fifty-two ovariectomized rats were randomized in oestrogen-treated and control groups. 17beta-oestradiol (1 mg/week) and normal saline (1 mg/week) were administered intramuscularly in the treatment and control groups for 2 months. After that, coronary capillary density and coronary vessel permeability were measured. The serum vascular endothelial growth factor (VEGF) level was also measured before and after the treatment. The results indicate that coronary capillary density (number of capillary per square millimetre) and coronary vessel permeability (fluorescence intensity) were significantly higher in the oestrogen-treated group than in the control group (628 +/- 26 per mm(2) versus 540 +/- 26 per mm(2); P < 0.05 and 207 +/- 10 versus 147 +/- 19 per gram tissue; P < 0.05). Oestrogen treatment increased serum VEGF level in the oestrogen-treated group compared to the control group (52 +/- 3 versus 33 +/- 6 pg/ml; P < 0.05), but interestingly VEGF was also increased in the control group after placebo treatment. It seems that high-dose oestrogen administration has angiogenic properties even in normoxic conditions. These angiogenic properties may result from oestrogen's direct effect on VEGF or other mechanisms, such as endothelial progenitor cell mobilization. Because of the broad effect of oestrogen on angiogenic growth factors and endothelial cells, more studies are required to clarify angiogenic properties of high-dose oestrogen.

Exercise restores coronary vascular function independent of myogenic tone or hyperglycemic status in db/db mice

Regulation of coronary function in diabetic hearts is an important component in preventing ischemic cardiac events but remains poorly studied. Exercise is recommended in the management of diabetes, but its effects on diabetic coronary function are relatively unknown. We investigated coronary artery myogenic tone and endothelial function, essential elements in maintaining vascular fluid dynamics in the myocardium. We hypothesized that exercise reduces pressure-induced myogenic constriction of coronary arteries while improving endothelial function in db/db mice, a model of type 2 diabetes. We used pressurized mouse coronary arteries isolated from hearts of control and db/db mice that were sedentary or exercised for 1 h/day on a motorized exercise-wheel system (set at 5.2 m/day, 5 days/wk). Exercise caused a approximately 10% weight loss in db/db mice and decreased whole body oxidative stress, as measured by plasma 8-isoprostane levels, but failed to improve hyperglycemia or plasma insulin levels. Exercise did not alter myogenic regulation of arterial diameter stimulated by increased transmural pressure, nor did it alter smooth muscle responses to U-46619 (a thromboxane agonist) or sodium nitroprusside (an endothelium-independent dilator). Moderate levels of exercise restored ACh-simulated, endothelium-dependent coronary artery vasodilation in db/db mice and increased expression of Mn SOD and decreased nitrotyrosine levels in hearts of db/db mice. We conclude that the vascular benefits of moderate levels of exercise were independent of changes in myogenic tone or hyperglycemic status and primarily involved increased nitric oxide bioavailability in the coronary microcirculation.

Exercise restores endothelial function independently of weight loss or hyperglycaemic status in db/db mice

AIMS/HYPOTHESIS

Exercise ameliorates oxidative stress-mediated diabetic vascular endothelial dysfunction through poorly defined mechanisms. We hypothesised that, in addition to improving metabolic parameters, upregulation of antioxidants such as superoxide dismutase (SOD) mediates exercise-induced reductions of oxidative stress and increased nitric oxide (NO) bioavailability, and also restores vasodilatation.

METHODS

Type 2 diabetic db/db and normoglycaemic wild-type mice were exercised at moderate intensity for 1 h a day for 7 weeks, leading to a 10% body weight loss. Sedentary animals or those undergoing a low-intensity exercise regimen causing non-significant weight loss were also used. We examined aortic endothelial cell function, NO bioavailability and various biomarkers of oxidative stress.

RESULTS

Moderate-intensity exercise lowered body weight, increased mitochondrial manganese SOD (MnSOD) and both total and phosphorylated (Ser1177) endothelial nitric oxide synthase (eNOS) protein production; it also reduced whole-body (plasma 8-isoprostane) and tissue oxidative stress (nitrotyrosine immunostaining or protein carbonyl levels in the aorta). Low-intensity exercise did not alter body weight; however, it upregulated cytosolic Cu/Zn-SOD instead of MnSOD, and still demonstrated all the above benefits in the db/db aorta. Importantly, both exercise protocols improved endothelial-dependent vasodilatation and NO bioavailability without altering hyperglycaemic status in db/db mice.

CONCLUSIONS/INTERPRETATION

Exercise reverses diabetic vascular endothelial dysfunction independently of improvements in body weight or hyperglycaemia. Our data suggest that upregulation of eNOS and specific SOD isoforms could play important roles in improving NO bioavailability, as well as in reversing endothelial dysfunction in type 2 diabetes patients through lifestyle modifications in the management of diabetes.

Vascular endothelial function in health and diseases

The vascular endothelium constitutes approximately 1% of body mass (1kg) and has a surface area of approximately 5000m(2). The endothelium is a multifunctional endocrine organ strategically placed between the vessel wall and the circulating blood, and has a key role in vascular homeostasis. The endothelium is both a target for and mediator of cardiovascular disease. The endothelium releases several relaxing and constricting factors, which can affect vascular homeostasis. Endothelial dysfunction, whether caused by physical injury or cellular damage, leads to compensatory responses that alter the normal homeostatic properties of the endothelium. In this review, we summarized some physiological aspects of endothelial function and then we discussed endothelial dysfunction during some pathological conditions.

Effect of exercise on augmented aortic vasoconstriction in the db/db mouse model of type-II diabetes

We evaluated the effects of exercise on the vascular constrictor responses to alpha-adrenergic stimulation in the db/db mice. Twenty male db/db and their age-matched wild-type (WT) mice were exercised (1 hour/day, five days a week). Mice were anesthetized 7 weeks later, thoracic aortae were mounted in wire myograph and constrictor responses to phenylephrine (PE, 1 nM-10 microM) were obtained. Citrate synthase activity measured in the thigh adductor muscle was significantly increased in db/db mice that were exercise trained. Maximal force generated by PE was markedly greater in db/db aortae and exercise did not attenuate this augmented contractile response. Vessels were incubated with inhibitors of nitric oxide synthase (L-NAME, 200 microM), endothelin receptors (bosentan, 10 microM), protein kinase C (PKC) (calphostin C, 5 microM), cyclooxygenase (indomethacin, 10 microM) or Rho-kinase (Y-27632, 0.1 microM). Only calphostin-C normalized the augmented PE-induced constriction in db/db and db/db- exercised mice to that observed in WT (p<0.05). Cumulative additions of indolactam, a PKC activator, induced significantly greater constrictor responses in aortic rings of db/db mice compared to WT and exercise did not affect this response. Our data suggest that the augmented vasoconstriction observed in the aorta of db/db mice is likely due to increased PKC activity and that exercise do not ameliorate this increased PKC-mediated vasoconstriction.

Effects modification of iron hematoxylin on neuron staining

Iron weigert staining methods is used as nuclear staining. In present study we introduce a modification iron weigert hematoxylin for staining neuron without astrocytes. Whole brain of adult wistar rats (12-13 week old) were removed, immersed in formaldehyde fixative and embedded in paraffin. Sections, 5-7 microm (from brain cortex, hippocampus, cerebellum) divided to three groups: one for staining by Hematoxyllin and eosin, second for staining by cresyl fast violet (that specially performed for Nisl substances in neuron) and last for staining by modification iron hematoxyllin methods, but different in quantity and quality. In new method general and specific architecture of neuron, nucleus and nuclear envelope was clearly visible reactions of neuron were predominant. Astrocyte did not respond to staining methods. Also spines (axon) of purkinje cells clearly visible. Modification iron weigert hematoxylin can be replacement to cost and time consuming chemical staining method for staining neurons.

The pharmacology of particulate matter air pollution-induced cardiovascular dysfunction

Since the London fog of 1952, in which more than 4000 people were killed in 4 days, the combined efforts of scientists from several disciplines, including those from the environmental health, clinical and biomedical disciplines, have raised serious concerns about the impact of air pollutants on human health. These environmental pollutants are rapidly being recognized as important and independent risk factors for several diseases such as asthma, chronic obstructive pulmonary disease, lung cancer, atherosclerosis, ischemic heart disease and stroke. Although the relative effects of particulate matter air pollution (aerodynamic diameter <10 microm, or PM(10)) are greater for respiratory than for cardiovascular deaths, the number of deaths attributable to PM(10) is much larger for cardiovascular than for respiratory reasons due to the higher prevalence of cardiovascular disease in the general population. This review summarizes current understanding of the mechanisms underlying the associations between PM(10) exposure and cardiovascular morbidity and mortality.

The effect of hypertension on serum nitric oxide and vascular endothelial growth factor concentrations. A study in DOCA-Salt hypertensive ovariectomized rats

CardioVascular Disease (CVD) accounts for considerable mortality and morbidity in developed countries. Most of the common forms of CVD, such as hypertension, are caused by functional and structural changes in endothelial function. This study was designed to study the effect of hypertension on serum Nitric Oxide (NO) and Vascular Endothelial Growth Factor (VEGF) concentrations in DOCA-Salt hypertensive ovariectomized rats. Thirty female rats were ovariectomized. Blood samples were taken and the animals were divided into hypertensive and control groups. Hypertension was induced by DOCA-Salt method. DOCA was injected 30 mg/kg of body weight subcutaneously, twice a week with NaCl 1% instead of tap water for drinking throughout the experiment. The control group received normal saline injection with usual drinking water. Results showed that serum NO concentration in DOCA-Salt hypertensive rats was lower than the control group (18.35 +/- 5.31, 45.01 +/- 12.54 micromol/l, respectively) (p < 0.05). Also, the mean serum VEGF concentration was raised after induced hypertension (120.55 +/- 8.11 vs. 88.58 +/- 2.24 pg/ml) (p < 0.05). In conclusion, reduced serum NO and increased serum VEGF concentrations in hypertensive animals support the concept of endothelial dysfunction in hypertensive subjects.

Serum level of vascular endothelial growth factor is increased by estrogen replacement therapy in normotensive and DOCA–Salt hypertensive ovariectomized rats

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of death in developed countries. Previous studies have shown that hormone replacement therapy reduces the risk of CVD in postmenopausal women, however, the mechanism remains unclear. This study was designed to evaluate the effect of estrogen on serum vascular endothelial growth factor (VEGF) concentration in normotensive and hypertensive ovariectomized rats.

METHODS

Forty-eight female rats were ovariectomized and randomly divided into 6 groups. Hypertension was induced by DOCA-Salt method. DOCA was injected 30 mg/kg of body weight subcutaneously, twice a week with NaCl 1% instead of tap water for drinking throughout the experiment. Estradiol valerate (Es) was injected 2 mg/week i.m. The groups were as follows: (i) DOCA (4 weeks) and DOCA+Es (6 weeks); (ii) DOCA (10 weeks); (iii) Normal saline (N/S) (4 weeks) and Es (6 weeks); (iv) N/S 10 weeks; (v) DOCA (4 weeks), and (vi) N/S (4 weeks). Serum VEGF concentration was measured in groups 1 to 4.

RESULTS

Results showed that in normotensive animals that received estrogen treatment, serum VEGF concentration was significantly higher than those not receiving estrogen (269+/-41 vs. 106+/-36 pg/ml) (P<0.05). In hypertensive group, serum VEGF level was also increased after estrogen therapy compare to those not receiving estrogen (326+/-55 vs. 121+/-28 pg/ml (P<0.05).

CONCLUSION

It is possible that the increase in serum VEGF concentration after estrogen therapy may contribute to the cardiovascular effects of estrogen in normotensive and hypertensive conditions.

Coronary vascular and aortic endothelial permeability during estrogen therapy: a study in DOCA-salt hypertensive ovariectomized rats

Cardiovascular disease (CVD) is a major source of morbidity and mortality in the Western World. Premenopausal and estrogen-treated postmenopausal women have a lower incidence of CVD. It has been suggested that circulating endogenous estrogens are probably responsible for this protection. This study investigated the hypothesis that the reduction of endothelial permeability is responsible for cardioprotective effects of estrogen in hypertensive animals. Fourty-four rats were ovariectomized and divided into five groups: groups 1, 2 and 4 received DOCA-salt and groups 3 and 5 received normal saline (N/S) injection for four weeks. Then, in groups 4 and 5 the blood pressure was measured. Group 1 received estradiol valerate and in groups 2 and 3 continued with DOCA-salt and N/S injection for six weeks, respectively. Endothelial permeability was measured by Evans Blue extraction method. There was no significant difference in endothelial permeability in coronary circulation in estrogen-treated group and controls (12.97+/-2.32 vs. 9.96+/-1.01, respectively). Also, aortic endothelial permeability in DOCA-salt hypertensive rats did not change significantly after estrogen treatment (28.34+/-3.65 vs. 41.60+/-5.98). This study showed that the cardioprotective effects of estrogen in DOCA-salt hypertensive animals are not mediated by a reduction of endothelial permeability.

The effect of estrogen on serum nitric oxide concentrations in normotensive and DOCA Salt hypertensive ovariectomized rats

BACKGROUND

Cardiovascular disease (CVD) is less prevalent in premenopausal women and women receiving estrogen replacement therapy (ERT) than in postmenopausal women or men. It proposed that the cardiovascular effects of estrogen are mediated, at least in part, through the ability of estrogen to increase nitric oxide (NO) synthesis. This study investigated the effect of estrogen on serum NO concentrations in normotensive and deoxycorticostrone acetate (DOCA) Salt hypertensive ovariectomized rats.

METHODS

Forty-eight female rats were ovariectomized and randomly divided into six groups. Hypertension was induced by DOCA Salt method. DOCA was injected 30 mg/kg of body weight subcutaneously, twice a week with NaCl 1% instead of tap water for drinking throughout the treatment period. Estradiol valerate (Es) was injected i.m. once a week. The groups were as follows: (2) DOCA (4 weeks) and DOCA+Es (6 weeks), (22) DOCA (10 weeks), (222) normal saline (N/S) (4 weeks)+Es (6 weeks), (2V) N/S (10 weeks), (V) DOCA (4 weeks), and (V2) N/S (4 weeks). Serum NO concentrations were measured in groups 1, 3 and 4 before and after treatment. Other groups were used as control.

RESULTS

Results showed that in normotensive animals, serum NO concentrations were increased after estrogen treatment significantly (90.20 +/- 18.67 vs. 19.11 +/- 1.78 micromol/l) (p < 0.05). Also, estrogen increased serum NO concentrations in DOCA Salt hypertensive rats (73.54 +/- 22.55 vs. 36.94 +/- 10.73 micromol/l) (p = 0.06).

CONCLUSION

Estrogen can increase serum NO concentrations in normotensive and DOCA Salt hypertensive animals and it may be important in cardiovascular effects of estrogen.

Coronary vascular and aortic endothelial permeability during estrogen therapy: a study in DOCA-salt hypertensive ovariectomized rats

Cardiovascular disease (CVD) is a major source of morbidity and mortality in the Western World. Premenopausal and estrogen-treated postmenopausal women have a lower incidence of CVD. It has been suggested that circulating endogenous estrogens are probably responsible for this protection. This study investigated the hypothesis that the reduction of endothelial permeability is responsible for cardioprotective effects of estrogen in hypertensive animals. Fourty-four rats were ovariectomized and divided into five groups: groups 1, 2 and 4 received DOCA-salt and groups 3 and 5 received normal saline (N/S) injection for four weeks. Then, in groups 4 and 5 the blood pressure was measured. Group 1 received estradiol valerate and in groups 2 and 3 continued with DOCA-salt and N/S injection for six weeks, respectively. Endothelial permeability was measured by Evans Blue extraction method. There was no significant difference in endothelial permeability in coronary circulation in estrogen-treated group and controls (12.97+/-2.32 vs. 9.96+/-1.01, respectively). Also, aortic endothelial permeability in DOCA-salt hypertensive rats did not change significantly after estrogen treatment (28.34+/-3.65 vs. 41.60+/-5.98). This study showed that the cardioprotective effects of estrogen in DOCA-salt hypertensive animals are not mediated by a reduction of endothelial permeability.