Éva Csongrádi

Induction of Heme Oxygenase 1 Attenuates Placental Ischemia–Induced Hypertension

Recent in vitro studies have reported that heme oxygenase 1 (HO-1) downregulates the angiostatic protein soluble fms-like tyrosine kinase 1 from placental villous explants and that the HO-1 metabolites CO and bilirubin negatively regulate endothelin 1 and reactive oxygen species. Although soluble fms-like tyrosine kinase 1, endothelin 1, and reactive oxygen species have been implicated in the pathophysiology of hypertension during preeclampsia and in response to placental ischemia in pregnant rats, it is unknown whether chronic induction of HO-1 alters the hypertensive response to placental ischemia. The present study examined the hypothesis that HO-1 induction in a rat model of placental ischemia would beneficially affect blood pressure, angiogenic balance, superoxide, and endothelin 1 production in the ischemic placenta. To achieve this goal we examined the effects of cobalt protoporphyrin, an HO-1 inducer, in the reduced uterine perfusion pressure (RUPP) placental ischemia model and in normal pregnant rats. In response to RUPP treatment, mean arterial pressure increases 29 mm Hg (136±7 versus 106±5 mm Hg), which is significantly attenuated by cobalt protoporphyrin (118±5 mm Hg). Although RUPP treatment causes placental soluble fms-like tyrosine kinase 1/vascular endothelial growth factor ratios to alter significantly to an angiostatic balance (1.00±0.10 versus 1.27±0.20), treatment with cobalt protoporphyrin causes a significant shift in the ratio to an angiogenic balance (0.68±0.10). Placental superoxide increased in RUPP (952.5±278.8 versus 243.9±70.5 relative light units/min per milligram) but was significantly attenuated by HO-1 induction (482.7±117.4 relative light units/min per milligram). Also, the preproendothelin message was significantly increased in RUPP, which was prevented by cobalt protoporphyrin. These data indicate that HO-1, or its metabolites, is a potential therapeutic for the treatment of preeclampsia.

Chronic nicotine exposure exacerbates acute renal ischemic injury

Recent epidemiological reports showed that smoking has a negative impact on renal function and elevates the renal risk not only in the renal patient but perhaps also in the healthy population. Studies suggested that nicotine, a major tobacco alkaloid, links smoking to renal dysfunction. While several studies showed that smoking/chronic nicotine exposure exacerbates the progression of chronic renal diseases, its impact on acute kidney injury is virtually unknown. Here, we studied the effects of chronic nicotine exposure on acute renal ischemic injury. We found that chronic nicotine exposure increased the extent of renal injury induced by warm ischemia-reperfusion as evidenced by morphological changes, increase in plasma creatinine level, and kidney injury molecule-1 expression. We also found that chronic nicotine exposure elevated markers of oxidative stress such as nitrotyrosine as well as malondialdehyde. Interestingly, chronic nicotine exposure alone increased oxidative stress and injury in the kidney without morphological alterations. Chronic nicotine treatment not only increased reactive oxygen species (ROS) production and injury but also exacerbated oxidative stress-induced ROS generation through NADPH oxidase and mitochondria in cultured renal proximal tubule cells. The resultant oxidative stress provoked injury through JNK-mediated activation of the activator protein (AP)-1 transcription factor in vitro. This mechanism might exist in vivo as phosphorylation of JNK and its downstream target c-jun, a component of the AP-1 transcription factor, is elevated in the ischemic kidneys exposed to chronic nicotine. Our results imply that smoking may sensitize the kidney to ischemic insults and perhaps facilitates progression of acute kidney injury to chronic kidney injury.

Increased levels of platelet activation markers are positively associated with carotid wall thickness and other atherosclerotic risk factors in obese patients

The role of platelets in the development of atherosclerosis and obesity-related prothrombotic state is still under investigation. In this cross-sectional cohort study, we measured the levels of different platelet activation markers and evaluated their relationship with carotid intima-media thickness (IMT) along with other atherosclerotic risk factors in obese patients with or without atherosclerotic co-morbidities. We enrolled 154 obese patients, including 98 with either hypertension, type 2 diabetes mellitus or dyslipidaemia, 56 without these co-morbidities and 62 age- and sex-matched healthy controls. Platelet P-selectin expression and the number of platelet-derived microparticles (PMPs) were measured by flow cytometry; soluble P-selectin levels were analysed by ELISA and Thr715Pro P-selectin polymorphism was determined by PCR-RFLP. Carotid IMT was examined by ultrasonography. The levels of platelet activation parameters were significantly elevated in all obese subjects with increased carotid IMT compared to healthy controls. There was no effect of Thr715Pro genotype on soluble P-selectin levels in obese individuals contrary to normal subjects. Significant and positive association was revealed between carotid IMT and platelet P-selectin (p<0.0001), soluble P-selectin (p=0.039) and PMP (p=0.0001) levels. After adjusting for multiple variables, independent association was found between soluble P-selectin and fibrinogen (p=0.007), PMP levels and body mass index (p<0.0001) as well as platelet P-selectin and carotid IMT (p=0.012) plus plasminogen activator inhibitor-1 (p=0.009). In conclusion, P-selectin and PMP levels showed positive associations with abnormal carotid IMT and other risk factors in obesity suggesting a critical role of enhanced platelet reactivity in atherosclerotic wall alteration.

Chronic HO-1 induction with cobalt protoporphyrin (CoPP) treatment increases oxygen consumption, activity, heat production and lowers body weight in obese melanocortin-4 receptor-deficient mice

Objective:Heme oxygenase-1 induction (HO-1) elicits chronic weight loss in several rodent models of obesity. Despite these findings, the mechanism by which HO-1 induction reduces body weight is unclear. Chronic HO-1 induction does not alter food intake, suggesting other mechanisms such as increases in metabolism and activity may be responsible for the observed reduction of body weight. In this study, we investigated the mechanism of weight loss elicited by chronic HO-1 induction in a model of genetic obesity due to melanocortin-4 receptor (MC4R) deficiency.Design:Experiments were performed on loxTB MC4R-deficient mice as well as lean controls. Mice were administered cobalt protoporphyrin (CoPP, 5 mg kg−1), an inducer of HO-1, once weekly, from 4 to 23 weeks of age. Body weights were measured weekly and fasted blood glucose and insulin, as well as food intake were determined at 18 weeks of age. Oxygen consumption (VO2), CO2 production (VCO2), activity and body heat production were measured at 20 weeks of age.Results:Chronic CoPP treatment resulted in a significant decrease in body weight from 5 weeks on in loxTB mice. Chronic CoPP treatment resulted in a significant decrease in fasted blood glucose levels, plasma insulin and a significant increase in plasma adiponectin levels in MC4R-deficient mice. Chronic CoPP treatment increased VO2 (47±4 vs 38±3 ml kg−1 per min, P<0.05) and VCO2 (44±7 vs 34±4 ml kg−1 per min, P<0.05) in treated vs non-treated, MC4R-deficient mice (n=4). Heat production (10%) and activity (18%) were also significantly (P<0.05) increased in CoPP-treated MC4R-deficient mice.Conclusion:Our results suggest that chronic HO-1 induction with CoPP induction elicits weight loss by increasing metabolism and activity by an MC4R-independent pathway.

Relationship of Serum Resistin Level to Traits of Metabolic Syndrome and Serum Paraoxonase 1 Activity in a Population with a Broad Range of Body Mass Index

UNLABELLED The relationship between resistin, one of the adipokines, and metabolic syndrome is not fully elucidated. Altered activity of the HDL-associated antioxidant enzyme paraoxonase 1 (PON1) that participates in the antioxidant defense mechanisms of HDL may have an important role in the obesity-related accelerated atherosclerosis. Inverse associations of PON1 with obesity and serum levels of leptin have been demonstrated. Our aim was to investigate the association of serum levels of resistin with (i) PON1 activity, and (ii) parameters of metabolic syndrome, including some that are additional for research. A total of 74 Caucasian subjects were recruited into the study and divided into 3 age and sex-matched groups. Group 1, 25 non-diabetic overweight/obese subjects with BMI of 28-39.9 kg/m (2); group 2, 25 non-diabetic obese patients with BMI >or=40 kg/m (2); and the control group 3, 24 healthy, normal-weight control subjects. Serum levels of resistin were correlated negatively with BMI (r=-0.27, P<0.05), waist circumference (r=-0.28, P<0.05), serum levels of leptin (r=-0.28, P<0.05), non-esterified fatty acids (NEFA) (r=-0.23, P<0.05), and HbA (1C) (r=-0.26, P<0.05), systolic BP (r=-0.28, P<0.05), and lipid peroxidation (measured by TBARS) (r=-0.40, P<0.01), and correlated positively with PON1 (r=0.24, P<0.05). No association was detected between the serum concentrations of resistin and the following investigated parameters: diastolic BP, levels of uric acid, glucose, insulin, or insulin resistance (measured by homeostasis model assessment, HOMA-IR), triglyceride, total cholesterol, LDL-C, and HDL-C. During multiple regression analyses BMI and TBARS were independent predictors of PON1, while age, gender, blood pressure, HOMA-IR, LDL-C, HDL-C, and resistin were not. CONCLUSIONS Among the study subjects, serum levels of resistin showed a positive, although not independent correlation with serum PON1, and a negative correlation with numerous parameters of the metabolic syndrome (i.e. adiposity, blood pressure, levels of leptin, free fatty acid, glycosylated hemoglobin, and lipid peroxidation). BMI and TBARS are independent predictors of PON1 activity.

Expression of Heme Oxygenase-1 in Thick Ascending Loop of Henle Attenuates Angiotensin II-Dependent Hypertension

Kidney-specific induction of heme oxygenase-1 (HO-1) attenuates the development of angiotensin II (Ang II) -dependent hypertension, but the relative contribution of vascular versus tubular induction of HO-1 is unknown. To determine the specific contribution of thick ascending loop of Henle (TALH) -derived HO-1, we generated a transgenic mouse in which the uromodulin promoter controlled expression of human HO-1. Quantitative RT-PCR and confocal microscopy confirmed successful localization of the HO-1 transgene to TALH tubule segments. Medullary HO activity, but not cortical HO activity, was significantly higher in transgenic mice than control mice. Enhanced TALH HO-1 attenuated the hypertension induced by Ang II delivered by an osmotic minipump for 10 days (139 ± 3 versus 153 ±2 mmHg in the transgenic and control mice, respectively; P<0.05). The lower blood pressure in transgenic mice associated with a 60% decrease in medullary NKCC2 transporter expression determined by Western blot. Transgenic mice also exhibited a 36% decrease in ouabain-sensitive sodium reabsorption and a significantly attenuated response to furosemide in isolated TALH segments. In summary, these results show that increased levels of HO-1 in the TALH can lower blood pressure by a mechanism that may include alterations in NKCC2-dependent sodium reabsorption.

Changes in Cerebral Blood Flow Detected by SPECT in Type 1 and Type 2 Diabetic Patients

Although macrovascular complications are typical for type 2 diabetes mellitus (T2DM), cerebral microvascular damage develops both in type 1 diabetes mellitus (T1DM) and T2DM. Color Doppler ultrasound is widely used for the examination of large- and medium-sized arteries, whereas SPECT and MRI are capable of identifying disturbances in the circulation of microvessels. Former studies using semiquantitative methods showed reduced reactivity and reserve capacity of cerebral vessels in both T1DM and T2DM patients. Our aim was to investigate whether there was any difference in the effects of the 2 types of diabetes mellitus on the global or regional cerebral blood flow, influenced by microvascular damage. Methods: In our study, the circulation and reserve capacity of cerebral arteries was examined using 99mTc-hexamethylpropylene amine oxime SPECT. A total of 17 individuals with T1DM and 43 individuals with T2DM were involved in the study. Results: Both basal and acetazolamide-challenged brain circulation were significantly lower in T2DM patients than in T1DM patients. We did not find a significant difference in the reserve capacity. However, the circulation of the frontal and occipital lobes changed differently in the 2 groups. The ratio of the circulation of the frontal and occipital lobes was significantly reduced both in basal and in acetazolamide-stimulated states in T2DM patients, independently of age (P < 0.0005 and P < 0.017), showing a greater relative decrease in the circulation of the frontal lobe in T2DM patients. Conclusion: There was a significant association between basal brain circulation and age, body mass index, and high-density lipoprotein (HDL), whereas acetazolamide-stimulated circulation showed a significant association with serum triglyceride and HDL.

Role of Carbon Monoxide in Kidney Function: Is a little Carbon Monoxide Good for the Kidney?

Carbon monoxide (CO) is an endogenously produced gas resulting from the degradation of heme by heme oxygense or from fatty acid oxidation. Heme oxygenase (HO) enzymes are constitutively expressed in the kidney (HO-2) and HO-1 is induced in the kidney in response to several physiological and pathological stimuli. While the beneficial actions of HO in the kidney have been recognized for some time, the important role of CO in mediating these effects has not been fully examined. Recent studies using CO inhalation therapy and carbon monoxide releasing molecules (CORMs) have demonstrated that increases in CO alone can be beneficial to the kidney in several forms of acute renal injury by limiting oxidative injury, decreasing cell apoptosis, and promoting cell survival pathways. Renal CO is also emerging as a major regulator of renal vascular and tubular function acting to protect the renal vasculature against excessive vasoconstriction and to promote natriuresis by limiting sodium reabsorption in tubule cells. Within this review, recent studies on the physiological actions of CO in the kidney will be explored as well as the potential therapeutic avenues that are being developed targeting CO in the kidney which may be beneficial in diseases such as acute renal failure and hypertension.

Investigation of Thr715Pro P-selectin gene polymorphism and soluble P-selectin levels in type 2 diabetes mellitus

Increased levels of soluble P-selectin (sP-selectin) have been shown in a number of different disorders, e.g. diabetes mellitus (DM) and cardiovascular disease (CVD). Several studies have attempted to demonstrate the association of the most intensively examined variant of P-selectin gene polymorphism (Thr715Pro) with sP-selectin levels in healthy subjects and in CVD, but contradictory data have been reported. To clarify the effect of Pro715 allele on the sP-selectin levels in type 2 DM, we analysed this polymorphism in diabetic patients and compared these data with sP-selectin levels. Type 2 DM patients (n = 119), 48 BMImatched non diabetic individuals - consisting mostly of overweight subjects - and 57 healthy volunteers were included in the study. TheThr715Pro polymorphism was analysed by PCR-RFLP, while sP-selectin levels were measured by ELISA. Significantly elevated sP-selectin levels were found in both DM and in overweight subjects compared to healthy controls. We confirmed previous reports that in healthy Pro715 allele carriers lower sPselectin levels could be measured; however, this difference was only significant in case of lean subjects. No significant difference was detected in sP-selectin level among DM and overweight individuals according to this genotype. However, significant difference was observed in sP-selectin levels in older DM patients compared to younger ones, but these levels were not accounted for by the Thr715Pro polymorphism. We suggest that in type 2 DM individuals, the significantly elevated sP-selectin levels are not due to the Thr715Pro P-selectin gene polymorphism.

Severe Symptomatic Hypocalcemia after Denosumab Administration in an End-Stage Renal Disease Patient on Peritoneal Dialysis with Controlled Secondary Hyperparathyroidism

We report the 1 case of severe, symptomatic hypocalcemia after denosumab (RANKL inhibitor) treatment in a peritoneal dialysis patient with secondary hyperparathyroidism and osteoporosis. A 58-year-old Caucasian female has been receiving chronic ambulatory peritoneal dialysis for four years secondary to polycystic kidney disease. Laboratory studies revealed: albumin-corrected calcium 9.0 mg/dL, phosphorus 5 mg/dL, alkaline phosphatase (ALP) 58 U/L [normal, 40-105], albumin 3.4 gm/dL [normal, 3.6-5.4] and intact parathyroid hormone (PTH) 315 pg/mL [normal, 40-72]. Marked osteoporosis was noted on the DXA scan, preventing her from renal transplantation considerations. She had failed conventional medical treatment, including per os calcium, monthly ergocalciferol (50,000 units/month), activated vitamin-D analog (doxercalciferol) and Case Study British Journal of Medicine & Medical Research, 3(4): 1398-1406, 2013 1399 renal-failure adjusted alendronate (70 mg twice a month). She was started on subcutaneous denosumab 60 mg every 6 months. After her first dose, she developed a progressive drop of calcium, phosphorus, bicarbonate and magnesium, in spite of massive escalation of doxercalciferol and calcium supplementation. Hypocalcemia nadired at 6.3 mg/dL with symptomatic tetany, requiring a brief hospitalization approximately 7 weeks after denosumab treatment. Her elevated PTH rose further transiently (647 pg/mL), along with ALP (123 U/L). Bone-mineral parameters normalized approximately 3 months after denosumab administration. The observed phenomenon resembled the phenotype of “hungry bone syndrome” observed after surgical parathyroidectomy. Conclusion: Treatment decisions based on bone densitometry results alone are not transposable between patients with or without end-stage renal disease. Denosumab may lead to critical hypocalcemia in dialysis patients and further aggravate existing secondary hyperparathyroidism.