Endothelial NOS expression and ischemia-reperfusion in isolated working rat heart from hypoxic and hyperoxic conditions

The effect of adaptation to hypoxia on cardiac tolerance to ischemia/reperfusion

The acute myocardial infarction (AMI) and sudden cardiac death (SCD), both associated with acute cardiac ischemia, are one of the leading causes of adult death in economically developed countries. The development of new approaches for the treatment and prevention of AMI and SCD remains the highest priority for medicine. A study on the cardiovascular effects of chronic hypoxia (CH) may contribute to the development of these methods. Chronic hypoxia exerts both positive and adverse effects. The positive effects are the infarct-reducing, vasoprotective, and antiarrhythmic effects, which can lead to the improvement of cardiac contractility in reperfusion. The adverse effects are pulmonary hypertension and right ventricular hypertrophy. This review presents a comprehensive overview of how CH enhances cardiac tolerance to ischemia/reperfusion. It is an in-depth analysis of the published data on the underlying mechanisms, which can lead to future development of the cardioprotective effect of CH. A better understanding of the CH-activated protective signaling pathways may contribute to new therapeutic approaches in an increase of cardiac tolerance to ischemia/reperfusion.

Liriodendrin, ameliorates hypertension by calcium channel blockade and enhancing enos expression in wistar rats

Introduction: Hypertension is found to be the prime cause ofdeath worldwide in spite of a number of available treatmentswhich suggests that there is a need of discovering new leadmolecules that would be more effective to treat cardiovasculardisease (CVD). Liriodendrin, the lignan phytoconstituent possessespotential pharmacological effects. Literature survey suggeststhat liriodendrin could be effective in mitigating hypertensionconsidering its structural similarity with reported cardiovascularprotective drugs. Hence liriodendrin is investigated to reveal itsmechanism of actions to support its antihypertensive property.Methods: Hypertension was induced in male wistar rats withDOCA salt. Hypertensive rats were treated with liriodendrin for4 weeks. Blood pressure, heart rate, body weight, lipid profile,serum nitrite levels, vascular reactivity to various catecholamines,in-vitro calcium channel blocking assays, antioxidantassay, determination of aortic calcium level, endothelial function,expression of eNOS analysis were studied.Result: Liriodendrin was found safe orally up to 2000 mg/kg. Itshowed a significant decrease in heart rate, blood pressure andmean arterial pressure. In-vitro study on the isolated rat aorta revealedthe calcium channel blocking potential of liriodendrin. Vascularreactivity to various catecholamines was normalized. Vascularendothelium was significantly protected by the enhancedrelease of nitric oxide and eNOS expression by the western blottechnique. Oxidative stress was also significantly reduced.Conclusion: Liriodendrin was found to be beneficial in hypertensionas it produced vasorelaxation by blocking calciumchannels, enhancing nitric oxide release, and reducing oxidativestress. Thus, liriodendrin may be useful to relieve hypertensionand cardiovascular complications.

Effect of melatonin versus injectable platelet rich fibrin on critical wound healing in submandibular salivary glands of diabetic rats

Background

Diabetes mellitus (DM) has harmful effects on body organs, including submandibular salivary glands (SMGs). It impairs wound healing process that follow sialoadenectomy. Yet there is no complete cure to diabetes, the available medications tend to control the side effects of DM or manage insulin resistance. Herein we tried to investigate the possible effects of injectable platelet rich fibrin (i-PRF) and melatonin on wound healing in diabetic rats.

Material and methods

Surgical defects were created in SMGs of 30 rats after confirmation of DM induction. Then rats were randomly and equally allocated into three groups. Group I served as control group; group II received topically applied i-PRF, and group III received topically administrated melatonin. After 28 days all rats were euthanized, and SMGs were processed for histological and biochemical analysis.

Results

Both i-PRF and melatonin caused significant reduction of malondialdehyde (P < 0.0001) and caspase-3 (P < 0.001) and significant increase in vascular endothelial growth factors (P = 0.001,0.009 respectively) that increased SMGs regenerative capacity when compared to diabetic group. Melatonin showed superior results regarding the histomorphological structure of SMGs.

Conclusion

Melatonin and i-PRF can be possible candidates for improvement of wound healing events in SMGs of diabetic rats.

Effect of combined endurance-resistance training and soy extract supplementation on expression of eNOS gene in ovariectomized rats

Introduction

Menopause is an independent risk factor for cardiovascular disease (CVD). Physical exercise and soybean diets have been suggested to reduce the risk of CVD in postmenopausal women. The purpose of this study was to investigate the effects of combined resistance and endurance (RE) training and soy extract (SOY) supplementation, both known to improve endothelial function, on expression of the eNOS gene in the heart of ovariectomized (OVX) rats.

Material and methods

Fifty female Wistar rats were divided into five groups: 1) sham (SHAM); 2) ovariectomy (OVX); 3) ovariectomy with soy extract supplementation (OVX + SOY); 4) OVX with RE training (OVX + RE); 5) and ovariectomy plus RE training with soy extract supplementation (OVX + RE + SOY). RE training and soy extract supplementation were administered alone or in combination for 6 weeks. The effects of these treatments on cardiac eNOS expression were measured using real-time PCR.

Results

Ovariectomy down-regulated cardiac eNOS gene expression; however, 6 weeks of SOY treatment or RE training reversed this effect (p ≤ 0.05). The combination of SOY plus RE was greater than RE or SOY alone in reversing estrogen-deficiency-caused eNOS down-regulation (p ≤ 0.05).

Conclusions

Our data suggest that the combinatory regimen of soy extract supplementation and regular RE training may be more beneficial to cardiovascular disease risk in a menopause rat model than either exercise or soy supplementation alone.

Differential Expression of Endothelial Nitric Oxide Synthase in Coronary and Cardiac Tissue in Hypoxic Fetal Guinea Pig Hearts

OBJECTIVE

The purpose of the present study was to quantify the effect of chronic hypoxia on endothelial nitric oxide synthase (eNOS) gene and protein expression of fetal coronary artery segments and cardiac tissue of fetal guinea pig hearts.

METHODS

Time-mated pregnant guinea pigs (term = 65 days) were housed in room air (NMX, n = 6) or in a hypoxic chamber containing 10.5% O2 for 14 days (HPX14, n = 6). At near term (60 days gestation), fetuses were excised from anesthetized animals via hysterotomy and hearts were removed and weighed. Both coronary artery segments and cardiac ventricle were excised from the same hearts, frozen, and stored at -80 C until ready for study. eNOS mRNA was quantified using real-time polymerase chain reaction (PCR) based on SYBR Green I labeling (BioRad Laboratories, Hercules, CA) using eNOS primers obtained from GeneBank normalized to 18S. eNOS proteins were quantified by Western immunoblotting using eNOS antibody (1:200) and normalized to normoxic controls. eNOS cell-specific localization in the fetal guinea pig heart was performed by double immunofluorescence staining.

RESULTS

Both coronary artery endothelial cells (EC) and cardiomyocytes (CM) but not vascular smooth muscle cells of normoxic hearts exhibited positive immunostaining of eNOS protein. Chronic hypoxia significantly (P < .05) increased both eNOS mRNA and protein levels of coronary artery segments (by 210.6% and 51.4%, respectively) but decreased (P < .05) mRNA and protein of cardiac tissue (by 50.0% and 40.6%, respectively) in the same hearts.

CONCLUSIONS

Chronic fetal hypoxia, after 14 days, induces sustained changes in eNOS gene and eNOS protein expression that differ between coronary and cardiac tissue in the fetal guinea pig heart. This study suggests that while the functional roles of altered eNOS expression in hypoxic fetal hearts remain unclear, the site at which eNOS expression is altered may be important in the adaptive response of the fetal heart to hypoxia.

A Scavenger Role for Nitric Oxide in the Aged Rat Kidney

Progressive ageing is associated with an increment of biomolecules modified through oxidation as a result of the action of free radicals deriving from reactive oxygen species that attack biomolecules. During ageing many alterations of renal functions have been reported. Renal ageing is associated with a progressive decline of glomerular filtration, renal blood flow and augmented vascular resistance. The kidney is a very important source of inducible nitric oxide synthase (iNOS) in both epithelial and vascular structures. In this study we have investigated mRNA and protein iNOS expression and localization and nitric oxide (NO) production in young and aged rats. An increased expression of iNOS occurs in rat kidney during ageing. In the aged rat, an increase in the values of both iNOS-RNA and iNOS protein was observed through rtPCR and Western blot analysis. The activities of three isoforms of NOS were also seen. In the aged rat kidney the production of NO decreased, due to the reduction of the activities of the three NOS. This suggests that in the aged rat a progressive increase of superoxide anion does not imply an increase in the production of NO which functions as a scavenger molecule, causing oxidative stress with accumulation of reactive oxygen species (ROS).

Differential hypoxic tolerance is mediated by activation of heat shock response and nitric oxide pathway

The fall in ambient oxygen pressure in high-altitude milieu elicits a wide range of physiological responses in the myocardium, which may differ from individual to individual. This condition, known as hypobaric hypoxia, invokes the cardioprotective heat shock response. The present study focuses on the role played by this ubiquitous response in mediating a differential tolerance to acute hypoxic stress. Sprague Dawley rats were exposed to simulated hypoxia equivalent to 223 mmHg pressure, screened on the basis of time taken for onset of a characteristic hyperventilatory response, and categorized as susceptible (<10 min), normal (10-25 min), or tolerant (>25 min). The tolerant animals displayed a significant upregulation of heat shock protein (Hsp)70/HSPA, evident through immunohistochemical staining of the cardiac tissue. The increased expression of transcription factor heat shock factor-1 led to the downstream activation of other chaperones, including Hsp90/HSPC, Hsp60/HSPD1, and Hsp27/HSPB1. The higher induction of HSPs in tolerant animals contributed to higher nitric oxide synthesis mediated by both endothelial nitric oxide synthase and inducible nitric oxide synthase activation. Conversely, susceptible animals showed significantly higher expression of the proinflammatory markers tumor necrosis factor alpha and nuclear factor kappa-light-chain enhancer of activated B cells in the myocardium. Evaluation of circulatory stress markers identified increased levels of reactive oxygen species, corticosterone and endothelin-1 in the susceptible animals highlighting their vulnerability to hypoxic stress. The heat shock response, through the action of chaperones and enhanced NO generation thus contributes substantially to the ability to sustain survival under acute sub lethal hypoxia.

Myocardial infarction induces early increased remote ADAM8 expression of rat hearts after cardiac arrest

BACKGROUND

A disintegrin and metalloproteinase-8 (ADAM8) is a potential surrogate of inflammation which has recently been associated with myocardial infarction. We evaluated in a rat cardiac transplantation model whether ischemia-reperfusion injury alone (IRI) or with early regional myocardial infarction (MI) would suffice to induce inflammatory myocardial remodeling and ADAM8 expression.

MATERIAL AND METHODS

Isogenic heterotopic cardiac transplantation after cardiac arrest was performed to 48 Fischer 344 rats to induce ischemia-reperfusion injury (IRI), of which 27 rats also underwent ligation of the left anterior coronary artery (LAD) of the heart to yield MI. Histology was performed at 0.5, 24 and 48 h after transplantation. ADAM8 was evaluated by qRT-PCR after graft harvesting.

RESULTS

After 0.5 and 48 h respectively, edematous intramyocardial artery nuclei and periadventitial inflammation were more prominent in MI after transplantation, as compared with IRI alone and Controls (57.0 vs 40.0 and 5.0; 1.9 vs 1.1 and 0.9, point score units, p < 0.05, respectively). The expression of ADAM-8 was increased in MI as compared with Controls (1.9 vs 1.0, 1.9 fold increase) at 48 h. In grafts with MI, ADAM8 was localized using immunohistochemistry to the vicinity of the area corresponding to the developing infarction as well as in intramyocardial arteries remote to the infarction area.

CONCLUSIONS

Remote histopathological changes of ischemic cardiac grafts are associated with increased expression of ADAM8 thus emphasizing a global myocardial impact of MI.

Upregulation of cardiac NO/NOS system during short-term hypoxia and the subsequent reoxygenation period

Hypoxia/reoxygenation (H/R) reportedly influences nitric oxide (NO) production and NO synthase (NOS) expression in the heart. Nonetheless, a number of works have shown controversial results regarding the changes that the cardiac NO/NOS system undergoes under such situations. Therefore, this study aims to clarify the behaviour of this system in the hypoxic heart by investigating seven different reoxygenation times. Wistar rats were submitted to H/R (hypoxia for 30 min; reoxygenation of 0, 2, 12, 24, 48, 72 h, and 5 days) in a novel approach to address the events provoked by assaults under such circumstances. Endothelial and inducible NOS (eNOS and iNOS) mRNA and protein expression, as well as enzymatic activity and enzyme location were determined. NO levels were indirectly quantified as nitrate/nitrite, and other S-nitroso compounds (NOx), which would act as NO-storage molecules. The results showed a significant increase in eNOS mRNA, protein and activity, as well as in NOx levels immediately after hypoxia, while iNOS protein and activity were induced throughout the reoxygenation period. These findings indicate that, not only short-term hypoxia, but also the subsequent reoxygenation period upregulate cardiac NO/NOS system until at least 5 days after the hypoxic stimulus, implying major involvement of this system in the changes occurring in the heart in response to H/R.

Changes of plasma asymmetric dimethylarginine levels after coronary artery bypass grafting

OBJECTIVES

We investigated whether coronary artery bypass grafting affects plasma asymmetric dimethylarginine (ADMA) concentrations and whether precardioplegic hyperoxia influences ADMA release from the heart.

DESIGN

Twenty two patients were randomized into control (n = 11) and hyperoxia (n = 11, ventilated with >96% oxygen before cardiopulmonary bypass) groups. Arterial and coronary sinus blood was sampled before cardioplegia and during early reperfusion. Arterial samples were drawn 60 min after declamping of the aorta, and on the first postoperative day.

RESULTS

Baseline arterial values of ADMA were not different between groups (0.59+/-0.18 micro mol/l control, 0.63+/-0.13 micro mol/l hyperoxia group). Negligible release of ADMA into coronary sinus was detected 20 min after cardioplegia. A significant decrease of arterial ADMA was observed by the first postoperative morning (0.42+/-0.16 micro mol/l in control, and 0.38+/-0.07 in hyperoxia group, p < 0.01 compared to baseline).

CONCLUSIONS

CABG with cardioplegia is associated with decrease of ADMA by the first postoperative morning. Reperfusion of cardioplegic heart did not result in significant release of ADMA. Pretreatment with hyperoxia had no influence on myocardial release and arterial levels of ADMA.

Chronic hypoxia increases inducible NOS-derived nitric oxide in fetal guinea pig hearts

Intrauterine hypoxia impacts fetal growth and organ function. Inducible nitric oxide synthase (iNOS) and neuronal NOS (nNOS) expression was measured to assess the response of fetal hearts to hypoxic (HPX) stress. Pregnant guinea pigs were housed in a hypoxic chamber (10.5% O2 for 14 d, n = 17) or room air [normoxic (NMX), n = 17]. Hearts of anesthetized near-term fetuses were removed. mRNA [hypoxia-inducible factor, (HIF)-1alpha, 1beta, 2alpha, 3alpha, iNOS, and nNOS] and protein levels (HIF-1alpha, iNOS, and nNOS) of fetal cardiac left ventricles were quantified by real time polymerase chain reaction (PCR) and Western analysis, respectively. Cardiac nitrite/nitrate levels were measured in the presence/absence of L-N6-(1-iminoethyl)-lysine (L-NIL), an iNOS inhibitor, administered to pregnant sows. Hypoxia significantly increased fetal cardiac HIF-1alpha and -2alpha mRNA, HIF-1alpha protein but not HIF-3alpha or -1beta mRNA levels. Hypoxia increased both iNOS mRNA (by 5x) and protein (by 23%) levels but had no effect on nNOS levels. Nitrite/nitrate levels were increased in HPX hearts by 2.5x and decreased with L-NIL by 67 +/- 14%. Thus, up-regulation of iNOS-derived nitric oxide (NO) generation is an important mechanism by which fetal hearts respond to chronic hypoxic stress.

Prenatal hypoxia induces increased cardiac contractility on a background of decreased capillary density

Background

Chronic hypoxia in utero (CHU) is one of the most common insults to fetal development and may be associated with poor cardiac recovery from ischaemia-reperfusion injury, yet the effects on normal cardiac mechanical performance are poorly understood.

Methods

Pregnant female wistar rats were exposed to hypoxia (12% oxygen, balance nitrogen) for days 10–20 of pregnancy. Pups were born into normal room air and weaned normally. At 10 weeks of age, hearts were excised under anaesthesia and underwent retrograde 'Langendorff' perfusion. Mechanical performance was measured at constant filling pressure (100 cm H₂O) with intraventricular balloon. Left ventricular free wall was dissected away and capillary density estimated following alkaline phosphatase staining. Expression of SERCA2a and Nitric Oxide Synthases (NOS) proteins were estimated by immunoblotting.

Results

CHU significantly increased body mass (P < 0.001) compared with age-matched control rats but was without effect on relative cardiac mass. For incremental increases in left ventricular balloon volume, diastolic pressure was preserved. However, systolic pressure was significantly greater following CHU for balloon volume = 50 μl (P < 0.01) and up to 200 μl (P < 0.05). For higher balloon volumes systolic pressure was not significantly different from control. Developed pressures were correspondingly increased relative to controls for balloon volumes up to 250 μl (P < 0.05). Left ventricular free wall capillary density was significantly decreased in both epicardium (18%; P < 0.05) and endocardium (11%; P < 0.05) despite preserved coronary flow. Western blot analysis revealed no change to the expression of SERCA2a or nNOS but immuno-detectable eNOS protein was significantly decreased (P < 0.001) in cardiac tissue following chronic hypoxia in utero.

Conclusion

These data offer potential mechanisms for poor recovery following ischaemia, including decreased coronary flow reserve and impaired angiogenesis with subsequent detrimental effects of post-natal cardiac performance.

Vascular endothelial growth factor expression (VEGF) in salivary glands of diabetic rats

This study is aimed at evaluating vascular endothelial growth factor (VEGF) expression in the salivary glands of diabetic rats. Our study was carried out on 1 group of male Wistar rats and 1 group of male Bio Breeding Wistar (BB/W) pre-diabetic rats. The first group (control) was composed of 11 rats (4 months old), and the other (test) of 11 rats (4 months old) which showed diabetes at day 85 of life. This kind of diabetes can be compared to human diabetes mellitus type 1. The submandibular glands were removed and processed for immunohistochemical analysis of VEGF. Diabetes increased salivary gland VEGF expression in the rats. The tissues analyzed (vascular endothelium, ductal endothelium, mucinous glands) always expressed VEGF, thus demonstrating that not only vascular endothelial cells, but also the other elements evaluated, have a role in the neoangiogenesis process. In both control and diabetic rats, the VEGF expression was constantly negative only in serous acini; thus demonstrating that serous acini are not involved in the neoangiogenetic processes. The vascular growth is a fundamental part of normal salivary gland development, therefore we speculate that strategies aimed at preservation or promotion of salivary gland VEGF expression may mitigate or attenuate diabetic-induced gland microvascular injury.

The hypoxia-inducible factor HIF-1 promotes intramyocardial expression of VEGF in infants with congenital cardiac defects

OBJECTIVES

The response to hypoxia is primarily mediated by the transcription factor hypoxia-inducible factor-1 (HIF-1) which leads to the induction of a variety of adaptive gene products including vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS). This study was designed to test the hypothesis that HIF-1 and its target genes would be upregulated in the ventricular myocardium of infants with cyanotic congenital cardiac defects.

METHODS

14 infants with cyanotic (n = 7) or acyanotic cardiac defects (n = 7) were investigated. Samples from the right ventricular myocardium taken immediately after aortic clamping were studied for protein expression and DNA-binding activity.

RESULTS

Protein levels of HIF-1alpha were significantly elevated in patients with cyanotic compared to acyanotic congenital heart disease and inversely correlated with the degree of hypoxemia. This response was accompanied by significantly enhanced HIF-1 DNA binding activity. Furthermore, protein levels of VEGF and eNOS were significantly higher in the myocardium of cyanotic than of acyanotic infants. To test the potential involvement of upstream regulatory pathways, activation of MAP kinases was determined. Intramyocardial levels of phosphorylated p38 MAP kinase, but not of ERK1/2 were significantly higher in infants with cyanotic compared to those with acyanotic congenital heart disease and inversely correlated to hypoxemia.

CONCLUSIONS

These findings show that chronic hypoxemia is associated with the induction and stabilization of the transcription factor HIF-1 as well as its target genes VEGF and eNOS in the myocardium of infants with cyanotic cardiac defects. Thus, stabilization of HIF-1 and induction of the adaptive hypoxia response could particularly participate in myocardial remodeling in children with congenital cardiac defects and chronic hypoxemia.

Nocturnal oxygen therapy prevents progress of congestive heart failure with central sleep apnea

BACKGROUND

Sleep disordered breathing has been reported to be associated with congestive heart failure (CHF). Nocturnal oxygen has been shown to abolish apnea. The aim of this study is to examine whether nocturnal oxygen reduces sympathetic nerve activity, and prevents progress of CHF.

METHODS

93 patients with left ventricular ejection fractions < 60%, were examined with overnight saturation monitoring for an oxygen desaturation index. Subjects with oxygen desaturation of 4% > or = 4/h were examined with polysomnography. Apnea-hypopnea index (AHI) was calculated as the total number of episodes of apnea and hypopnea per hour of sleep. We started nocturnal oxygen for the patients with AHI > or = 20. Urinary and plasma catecholamines concentrations, serum brain natriuretic peptide, human atrial natriuretic peptide, and endothelial nitric oxide synthase levels were measured before and after starting oxygen.

RESULTS

Compared among the three groups, CHF with central sleep apnea (CHF-CSA) group had significantly higher 24-h urinary adrenaline (CHF-CSA: 4.411+/-2.940 micromol/day, CHF with obstructive sleep apnea (CHF-OSA): 2.686+/-1.084 micromol/day, CHF without apnea (CHF-N): 3.178+/-1.778 micromol/day, P<0.05). Oxygen therapy significantly decreased AHI and 4 serum BNP levels (from 91.75+/-80.35 pg/ml to 52.75+/-45.70 pg/ml, mean change=33.85 pg/ml, P=0.0208). Serum eNOS levels were lower in CHF-CSA group and CHF-OSA group than in CHF-N group (CHF-CSA: 15.89+/-10.75 pg/ml, CHF-OSA: 7.46+/-3.91 pg/ml, CHF-N: 27.33+/-14.83 pg/ml, P<0.05).

CONCLUSIONS

Nocturnal oxygen may prevent progress of CHF with central sleep apnea.

Modulation of MCP-1 and iNOS by 50-Hz sinusoidal electromagnetic field

The purpose of this study was to investigate whether overnight exposure to 1 mT-50 Hz extremely low-frequency sinusoidal electromagnetic field (EMF) affects the expression and production of inducible nitric oxide synthase (iNOS) and monocyte chemotactic protein-1 (MCP-1) in human monocytes. RT-PCR and Western blot analysis demonstrate that EMF exposure affects the expression of iNOS and MCP-1 in cultured human mononuclear cells at the mRNA level and protein synthesis. Interestingly, the effects of EMF exposure clearly differed with respect to the potentiation and inhibition of iNOS and MCP-1 expression. Whereas iNOS was down-regulated both at the mRNA level and at the protein level, MCP-1 was up-regulated. These results provide helpful information regarding the EMF-mediated modulation of the inflammatory response in vivo. However, additional studies are necessary to demonstrate that EMF acts as a nonpharmacological inhibitor of NO and inducer of MCP-1 in some diseases where the balance of MCP-1 and NO may be important.

Chronic hypoxia decreases endothelial nitric oxide synthase protein expression in fetal guinea pig hearts

OBJECTIVES

The underlying cellular mechanisms mediating hypoxia-induced adaptations in the fetus are poorly understood. We tested the hypothesis that hypoxia up-regulates endothelial nitric oxide synthase (NOS3, type III) protein expression in fetal hearts similar to that observed in adult hearts as a cardioprotective adaptation. This study investigates the effect of chronic hypoxia on NOS3 protein expression in hearts and carotid arteries of fetal guinea pigs exposed to normoxia or intrauterine hypoxia.

METHODS

Time-mated pregnant guinea pigs (term = 65 days) were housed in either normoxic room air (NMX) or exposed to 12% O(2) (hypoxia; HPX) for 14 or 28 days of duration. At near term ( approximately 60 days of gestation), pregnant mothers were anesthetized and fetal guinea pig hearts and carotid arteries were excised from NMX and HPX animals and frozen until ready for study. In addition, hearts were also excised from anesthetized adult nonpregnant female guinea pigs exposed to either NMX or HPX for 14 days. NOS3 protein was extracted from all tissues and quantified using Western blot analysis. Fetal heart samples were also prepared for localization of NOS3 protein using immunohistochemistry.

RESULTS

Chronic hypoxia increased both maternal and fetal hematocrit after 28 days of duration. HPX decreased NOS3 protein levels in fetal guinea pig hearts by 29% after 28 days compared to NMX controls. In contrast, HPX increased both NOS3 protein levels in adult hearts by 62% and fetal carotid arteries by fourfold after 14 days of exposure compared to their respective NMX controls. Positive immunostaining of NOS3 protein of fetal hearts was localized in both cardiomyocytes and endothelial cells.

CONCLUSION

Contrary to our hypothesis, the hypoxia-induced decrease in fetal guinea pig heart NOS3 protein contrasts to the protein levels measured in either adult hearts or fetal carotid arteries. These results suggest that the NOS protein expression is altered differently by hypoxia in fetal and adult hearts and in a peripheral fetal artery exposed to the same level of hypoxia. Thus, the functional role of NO in the fetal heart during hypoxia may differ from that of the adult.

MCP-1 and MIP-2 expression and production in BB diabetic rat: effect of chronic hypoxia

Type 1 (insulin-dependent) diabetes mellitus is an autoimmune disease characterized by the failure to synthesize or secrete insulin, and diabetics are likely to suffer complications that include kidney and heart disease, as well as loss of sight, angiopathy, tissue hypoxia, reduction in organ blood flow, impaired wound healing, respiratory infections, arteriosclerosis, etc., thus diabetes very closely resembles a state of chronic hypoxia. It is now well recognized that hypoxia is an important environmental stimulus capable of modulating the expression of many genes involved in energy metabolism. The diabetic metabolic stress resulting from impaired energy metabolism, which produce altered production of inflammatory mediators, may increase the risk of oxidative injury. The aim was to investigate whether production of MIP-2 and MCP-1 are implicated in the pathogenesis of diabetes, and if the regulatory effects of these chemokines are affected by hypoxia. Two groups of rats, diabetic and non-diabetic, were kept in normoxic room air conditions or subjected to chronic hypoxia. Expression and production of chemokines were measured by RT-PCR and ELISA assay. In diabetic rats, we found a marked increase of MCP-1 when compared with non-diabetic rats (783.5+/- 49 versus 461.9 +/- 27), while no significant differences were detected for MIP-2 levels. Hypoxia selectively modulated chemokines production, since MCP-1 expression and production was up-regulated in the diabetic groups (783.5+/- 49 versus 461.9+/- 27), but down-regulated MIP-2 expression and production (87.8+/- 23 versus 522.1+/- 72). Our data point to MCP-1 and MIP-2 as important components in the pathophysiology of diabetes, and hypoxia is an important and potent environmental stimulus capable of modulating the expression and production of these chemokines.

Cardioprotective effects of nitroparacetamol and paracetamol in acute phase of myocardial infarction in experimental rats

We aimed to determine whether nitroparacetamol (NO-paracetamol) and paracetamol exhibit cardioprotective effects. Myocardial infarction (MI) was induced in rats, and drug treatment was started 1 wk before surgery. Mortality rate and infarct size at 2 days after MI were compared. Treatment groups included vehicle (saline), paracetamol (5 mg x kg(-1) x day(-1)) and NO-paracetamol (15 mg x kg(-1) x day(-1)). Mortality rates for vehicle (n = 80), paracetamol (n = 79), and NO-paracetamol (n = 76) groups were 37.5%, 21.5%, and 26.3%, respectively. Infarct size for the vehicle group was 44.8% (+/-6.1%) of the left ventricle (LV). For the paracetamol and NO-paracetamol groups, infarct size was 31.3% (+/-5.6%) and 30.7% (+/-8.1%) of the LV, respectively. Both paracetamol- and NO-paracetamol-treated groups showed increased activities of catalase and SOD compared with the vehicle group. They could attenuate endothelial, inducible, and neuronal nitric oxide synthase and cyclooxygenase-1 and -2 gene expression after MI. The observation indicates the potential clinical significance of the cardioprotective effects of these drugs.

Inhibition of iNOS with 1400W improves contractile function and alters nos gene and protein expression in reperfused skeletal muscle

This study examined the effects of 1400W, an inhibitor of inducible nitric oxide (iNOS), on contractile function and iNOS expression in reperfused skeletal muscle. The right extensor digitorum longus (EDL) muscle of 104 rats underwent a sham operation or 3-h ischemia followed by 3-h or 24-h reperfusion (I/R). Rats received 3 mg/kg 1400W, 10 mg/kg 1400W, or water subcutaneously. Results showed that EDL contractile function in both 1400W-treated groups significantly outperformed the controls at 24-h but not at 3-h reperfusion. Although iNOS expression increased in all three I/R groups during reperfusion, a significantly smaller increase was found in 1400W-treated muscles after 3-h reperfusion, and more dramatically so after 24-h reperfusion. Our results indicate that inhibition of iNOS preserved the contractile function in reperfused skeletal muscle, perhaps via downregulating iNOS expression. Protection by 1400W at 24-h reperfusion suggests that the role of iNOS in exaggerating reperfusion injury is more prominent in the later stages of injury.

Nitric oxide synthase in healthy and inflamed human dental pulp

Nitric oxide synthase (NOS) plays a significant role in the pathogenesis of pulpitis. In this study, we hypothesized the existence of endothelial (eNOS) and inducible (iNOS) enzyme isoforms in human dental pulp. Extracted third molar pulps were divided into groups based on clinical diagnosis: healthy, hyperemic, and irreversible pulpitis. We have localized the eNOS and iNOS by immunohistochemistry and have tested their mRNA expression by RT-PCR and protein levels by Western blots. eNOS is present in the endothelial cells and odontoblasts of the healthy pulp, but an elevation of eNOS mRNA and protein levels with a concomitant dilation of vessels was characteristic under pathological conditions. Healthy pulp tissue failed to exhibit any iNOS; however, acute inflammation enhanced the mRNA and protein levels of iNOS, mainly in the leukocytes. There are differences in localization and expression between eNOS and iNOS in healthy and inflamed dental pulp.

Left ventricular wall stress as a direct correlate of cardiomyocyte apoptosis in patients with severe dilated cardiomyopathy

BACKGROUND

Apoptosis has been implicated as a possible mechanism in the development of heart failure (HF), but the mechanisms involved remain unclear. In patients with severe dilated cardiomyopathy, we evaluated cardiomyocyte apoptosis in relation to the transmural distribution of Bax and Bcl-2 proteins (2 molecules inhibiting or promoting apoptosis, respectively) and left ventricular wall stresses.

METHODS

We studied the presence and distribution of cardiomyocyte apoptosis in 90 tissue samples obtained from 8 patients who were undergoing left ventricular reduction with the Batista (ventricular remodeling) operation. Apoptosis was assessed in tissue samples taken from the entire left ventricular thickness (subdivided in subepicardial, midmyocardial, and subendocardial sections) with the terminal deoxynucleotidyl transferase mediated dUTP-biotin nick-end labeling (TUNEL) technique and DNA agarose gel electrophoresis. The expression of Bcl-2 and Bax proteins were determined with both Western analysis and immunohistochemistry.

RESULTS

TUNEL-positive cells (apoptotic index) were 2.3% +/- 1.4%. Apoptotic cells were predominantly distributed in the subendocardium, where higher levels of Bax protein were detected. The ratio of Bax to Bcl-2 proteins (Bax/Bcl-2) was similar in the midmyocardium or subepicardium, but increased in the subendocardium, where it was directly related to systolic wall stress (y = 0.009x - 0.629; r2 = 0.85, P <.001). The apoptotic index was also directly related to systolic and end-diastolic stresses calculated from hemodynamic and echocardiographic data (r2 = 0.77, P <.001 and r2 = 0.40, P <.01, respectively).

CONCLUSIONS

In patients with dilated cardiomyopathy, in whom cardiomyocyte apoptosis is an important cause of cell loss, apoptosis is more extensively localized in the subendocardium and strictly related to ventricular wall stresses and the Bax/Bcl-2 ratio.

Effect of chronic hypoxia on inducible nitric oxide synthase expression in rat myocardial tissue

The purpose of our study was to evaluate the effect of chronic exposure to low cellular oxygen tension (90% N2 and 10% O2 for 14 days) in inducing apoptosis and activation of transcription and translation of inducible nitric oxide (NO) synthase (iNOS) in rat hearts tissue. Rats were divided into four groups: normoxic, hypoxic, rats maintained in normoxic condition for 7 days and subjected to hypoxic conditions for another 7 days, and rats maintained in hypoxic condition for 7 days and subjected to normoxic conditions for another 7 days. At the 7th and 14th days, five rats from each group were sacrificed. Immunohistochemical and Western blot analysis were performed on myocardial tissue to reveal the presence of iNOS. Expression of iNOS was determined by RT-PCR. Apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and by detection of internucleosomal DNA fragmentation by electrophoresis. Electrophoretic analysis of DNA showed oligonucleosomal fragmentation in the hypoxic groups, but no ladder was observed in the other groups. This data was confirmed through end labeling with streptavidin-biotin (biotin d-UTP). iNOS expression was evaluated through immunohistochemical techniques (Ab anti-iNOS) and Western blotting, and the results were quantified with a computerized imaging analysis. The expression of iNOS protein was greater in the hypoxic groups; in the normoxic groups, only a nonspecific background was detected. This data was supported with results obtained through RT-PCR, which showed the specific transcription of mRNA for iNOS in the same experimental conditions. In addition, the iNOS activity was also evaluated and was found to be more active in the hypoxic groups (0.1 +/- 0.01 vs 0.02 +/- 0.003). The present study shows that exposure to low oxygen tension is capable of inducing programmed cell death and activating iNOS.

Chronic and intermittent hypoxia induce different degrees of myocardial tolerance to hypoxia-induced dysfunction

Chronic hypoxia (CH) is believed to induce myocardial protection, but this is in contrast with clinical evidence. Here, we test the hypothesis that repeated brief reoxygenation episodes during prolonged CH improve myocardial tolerance to hypoxia-induced dysfunction. Male 5-week-old Sprague-Dawley rats (n = 7-9/group) were exposed for 2 weeks to CH (F(I)O(2) = 0.10), intermittent hypoxia (IH, same as CH, but 1 hr/day exposure to room air), or normoxia (N, F(I)O(2) = 0.21). Hearts were isolated, Langendorff perfused for 30 min with hypoxic medium (Krebs-Henseleit, PO(2) = 67 mmHg), and exposed to hyperoxia (PO(2) = 670 mm Hg). CH hearts displayed higher end-diastolic pressure, lower rate x pressure product, and higher vascular resistance than IH. During hypoxic perfusion, anaerobic mechanisms recruitment was similar in CH and IH hearts, but less than in N. Thus, despite differing only for 1 hr daily exposure to room air, CH and IH induced different responses in animal homeostasis, markers of oxidative stress, and myocardial tolerance to reoxygenation. We conclude that the protection in animals exposed to CH appears conferred by the hypoxic preconditioning due to the reoxygenation rather than by hypoxia per se.

Overexpression of cytochrome P450 CYP2J2 protects against hypoxia-reoxygenation injury in cultured bovine aortic endothelial cells

CYP2J2 is abundant in human heart and its arachidonic acid metabolites, the epoxyeicosatrienoic acids (EETs), have potent vasodilatory, antiinflammatory and cardioprotective properties. This study was designed to examine the role of CYP2J2 in hypoxia-reoxygenation-induced injury in cultured bovine aortic endothelial cells (BAECs). Early passage BAECs were exposed to 24-h hypoxia followed by 4-h reoxygenation (HR). HR resulted in cell injury, as indicated by significant increases in lactate dehydrogenase (LDH) release and trypan blue stained cells (p < 0.01) and was associated with a decrease in CYP2J2 protein expression. Transfection of BAECs with the CYP2J2 cDNA resulted in increased CYP2J2 expression and arachidonic acid epoxygenase activity, compared with cells transfected with an irrelevant green fluorescent protein (GFP) cDNA. HR induced significant injury in GFP-transfected BAECs, as indicated by increases in LDH release and trypan blue-stained cells (p < 0.01); however, the HR-induced injury was markedly attenuated in CYP2J2-transfected cells (p < 0.01). HR increased cellular 8-iso-prostaglandin F(2alpha) (p < 0.05), and decreased eNOS expression, L-arginine uptake and conversion, and nitrite production (p < 0.01) in GFP-transfected BAECs. CYP2J2 transfection attenuated the HR-induced increase in 8-iso-prostaglandin F(2alpha) (p < 0.05) and decreased the amount of extracellular superoxide detected by cytochrome c reduction under normoxic conditions (p < 0.05) but did not significantly affect HR-induced decreases in eNOS expression, L-arginine uptake and conversion, and nitrite production. Treatment of BAECs with synthetic EETs and/or epoxide hydrolase inhibitors also showed protective effects against HR injury (p < 0.05). These observations suggest: (1) HR results in endothelial injury and decreased CYP2J2 expression; (2) transfection with the CYP2J2 cDNA protects against HR injury; and (3) the cytoprotective effects of CYP2J2 may be mediated, at least in part, by antioxidant effects.