Melatonin reduces renal interstitial inflammation and improves hypertension in spontaneously hypertensive rats

Orchestrated feedback regulation between melatonin and sex hormones involving GPER1-PKA-CREB signaling in the placenta

Maintaining placental endocrine homeostasis is crucial for a successful pregnancy. Pre-eclampsia (PE), a gestational complication, is a leading cause of maternal and perinatal morbidity and mortality. Aberrant elevation of testosterone (T0 ) synthesis, reduced estradiol (E2 ), and melatonin productions have been identified in preeclamptic placentas. However, the precise contribution of disrupted homeostasis among these hormones to the occurrence of PE remains unknown. In this study, we established a strong correlation between suppressed melatonin production and decreased E2 as well as elevated T0 synthesis in PE placentas. Administration of the T0 analog testosterone propionate (TP; 2 mg/kg/day) to pregnant mice from E7.5 onwards resulted in PE-like symptoms, along with elevated T0 production and reduced E2 and melatonin production. Notably, supplementation with melatonin (10 mg/kg/day) in TP-treated mice had detrimental effects on fetal and placental development and compromised hormone synthesis. Importantly, E2 , but not T0 , actively enhanced melatonin synthetase AANAT expression and melatonin production in primary human trophoblast (PHT) cells through GPER1-PKA-CREB signaling pathway. On the other hand, melatonin suppressed the level of estrogen synthetase aromatase while promoting the expressions of androgen synthetic enzymes including 17β-HSD3 and 3β-HSD1 in PHT cells. These findings reveal an orchestrated feedback mechanism that maintains homeostasis of placental sex hormones and melatonin. It is implied that abnormal elevation of T0 synthesis likely serves as the primary cause of placental endocrine disturbances associated with PE. The suppression of melatonin may represent an adaptive strategy to correct the imbalance in sex hormone levels within preeclamptic placentas. The findings of this study offer novel evidence that identifies potential targets for the development of innovative therapeutic strategies for PE.

Renal functional and structural alterations induced by intramuscular injection of Bothrops leucurus venom

Acute kidney injury (AKI) is the main cause of death from Bothrops snakebite. Although many studies have investigated the nephrotoxicity induced by other Bothrops species, no study has assessed the renal alterations induced by intramuscular (i.m.) injection of Bothrops leucurus venom. In this study, we evaluated the nephrotoxicity induced by B. leucurus venom by analyzing renal function and histology. Wistar rats were submitted to i. m. injection of B. leucurus venom or saline and divided into two groups: Control group (C), rats submitted to i. m. injections of saline, and B. leucurus group (Bl), rats submitted to i. m. injections of B. leucurus venom (1 mg/kg). After venom or saline injection, serum and urine were collected to measure creatinine, albumin, sodium, and potassium levels. The glomerular filtration rate (GFR), urinary flow urinary, creatinine/serum creatinine ratio, and albuminuria-urinary creatinine ratio were determined. All rats were euthanized 72 h following the injections, and the kidneys were removed for histology and immunohistochemical studies. B. leucurus experimental envenoming was accompanied by an increase of 236% in serum creatine kinase activity in the Bl group. The weights of the right and left kidneys were, respectively, 26 and 22% higher in rats of the Bl group than in control rats. Regarding renal function, the Bl group showed a decrease of 37% in GFR compared to control group. The rats of the Bl group also presented increased cortical (8.20 ± 1.35) and medullar (6.17 ± 2.00) tubulointerstitial lesion area when compared to control group (0.02 ± 0.00) (1.20 ± 0.73), respectively. The number of macrophages was also higher in the renal cortex (6.66 ± 0.06) and medulla (1.22 ± 0.10) of rats from the Bl group when compared to control rats (1.04 ± 0.55), (0.65 ± 0.10), respectively. Our results indicate that B. leucurus venom promoted significant histological and functional renal alterations following intramuscular inoculation, which simulates the majority of snakebites observed in the clinical practice.

New insights into the mechanisms of diabetic kidney disease: Role of circadian rhythm and Bmal1

It is common for diabetic kidney disease (DKD) to be complicated by abnormal blood glucose, blood lipids, and blood pressure rhythms. Thus, it is essential to examine diagnostic and treatment plans from the perspective of circadian disruption. This brief review discusses the clinical relevance of circadian rhythms in DKD and how the core clock gene encoding brain and muscle arnt-like protein 1 (BMAL1) functions owing to the importance of circadian rhythm disruption processes, including the excretion of urinary protein and irregular blood pressure, which occur in DKD. Exploring Bmal1 and its potential mechanisms and signaling pathways in DKD following contact with Sirt1 and NF-κB is novel and important. Finally, potential pharmacological and behavioral intervention strategies for DKD circadian rhythm disturbance are outlined. This review aids in unveiling novel, potential molecular targets for DKD based on circadian rhythms.

A new immune disease: systemic hypertension

Systemic hypertension is the most common medical comorbidity affecting the adult population globally, with multiple associated outcomes including cerebrovascular diseases, cardiovascular diseases, vascular calcification, chronic kidney disease, metabolic syndrome and mortality. Despite advancements in the therapeutic field approximately one in every five adult patients with hypertension is classified as having treatment-resistant hypertension, indicating the need for studies to provide better understanding of the underlying pathophysiology and the need for more therapeutic targets. Recent pre-clinical studies have demonstrated the role of the innate and adaptive immune system including various cell types and cytokines in the pathophysiology of hypertension. Moreover, pre-clinical studies have indicated the potential beneficial effects of immunosuppressant medications in the control of hypertension. Nevertheless, it is unclear whether such pathophysiological mechanisms and therapeutic alternatives are applicable to human subjects, while this area of research is undoubtedly a rapidly growing field.

Hypotensive effects of melatonin in rats: Focus on the model, measurement, application, and main mechanisms

The hypotensive effects of melatonin are based on a negative correlation between melatonin levels and blood pressure in humans. However, there is a positive correlation in nocturnal animals that are often used as experimental models in cardiovascular research, and the hypotensive effects and mechanism of melatonin action are often investigated in rats and mice. In rats, the hypotensive effects of melatonin have been studied in normotensive and spontaneously or experimentally induced hypertensive strains. In experimental animals, blood pressure is often measured indirectly during the light (passive) phase of the day by tail-cuff plethysmography, which has limitations regarding data quality and animal well-being compared to telemetry. Melatonin is administered to rats in drinking water, subcutaneously, intraperitoneally, or microinjected into specific brain areas at different times. Experimental data show that the hypotensive effects of melatonin depend on the experimental animal model, blood pressure measurement technique, and the route, time and duration of melatonin administration. The hypotensive effects of melatonin may be mediated through specific membrane G-coupled receptors located in the heart and arteries. Due to melatonin's lipophilic nature, its potential hypotensive effects can interfere with various regulatory mechanisms, such as nitric oxide and reactive oxygen species production and activation of the autonomic nervous and circadian systems. Based on the research conducted on rats, the cardiovascular effects of melatonin are modulatory, delayed, and indirect.

AHR canonical pathway: in vivo findings to support novel antihypertensive strategies

Essential hypertension (HTN) is a disease where genetic and environmental factors interact to produce a high prevalent set of almost indistinguishable phenotypes. The weak definition of what is under the umbrella of HTN is a consequence of the lack of knowledge on the players involved in environment-gene interaction and their impact on blood pressure (BP) and mechanisms. The disclosure of these mechanisms that sense and (mal)adapt to toxic-environmental stimuli might at least determine some phenotypes of essential HTN and will have important therapeutic implications. In the present manuscript, we looked closer to the environmental sensor aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor involved in cardiovascular physiology, but better known by its involvement in biotransformation of xenobiotics through its canonical pathway. This review aims to disclose the contribution of the AHR-canonical pathway to HTN. For better mirror the complexity of the mechanisms involved in BP regulation, we privileged evidence from in vivo studies. Here we ascertained the level of available evidence and a comprehensive characterization of the AHR-related phenotype of HTN. We reviewed clinical and rodent studies on AHR-HTN genetic association and on AHR ligands and their impact on BP. We concluded that AHR is a druggable mechanistic linker of environmental exposure to HTN. We conclude that is worth to investigate the canonical pathway of AHR and the expression/polymorphisms of its related genes and/or other biomarkers (e.g. tryptophan-related ligands), in order to identify patients that may benefit from an AHR-centered antihypertensive treatment.

Increased endothelial nitric oxide production after low level lead exposure in rats involves activation of angiotensin II receptors and PI3K/Akt pathway

BACKGROUND

Lead induces endothelial dysfunction and hypertension in humans and animals. Seven-day exposure to a low dose in rats reduces vasocontractile responses and increases nitric oxide (NO) bioavailability. We hypothesized that this occurs by angiotensin II receptors (AT1/AT2) activation.

MATERIALS AND RESULTS

Wistar rats were exposed to lead acetate (1 st dose 4 μg/100 g, subsequent dose 0.05 μg/100 g/day i.m., 7 days) or saline (control group). Lead acetate exposure reduced the phenylephrine vascular response. Pre-incubations with NO synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) or phosphatidylinositol 3-kinase (PI3K) inhibitor (wortmannin) increased the contractile response in aortas from lead-treated rats. Pre-incubation with AT2 antagonist (PD123319) restored normal vascular contraction, and both PD123319 or AT1 antagonist (losartan) impeded the potentiated effects of L-NAME and wortmannin. Reinforcing those findings, increased NO bioavailability was blunted by AT1 and AT2 antagonists without summative effect when co-incubated. Finally, to test whether activation of AT1 could upregulate AT2 to increase NO bioavailability rats were simultaneously exposed to lead acetate and treated with losartan (15 mg/kg/day, orally given). Losartan prevented changes on vascular reactivity and endothelial modulation in lead-exposed group. Moreover, incubation with PD123319 had no more effects in aortic from losartan-treated rats.

CONCLUSION

Our results suggest that low-dose lead acetate exposure induces an increase of NO involving mainly AT2 receptor activation and the PI3K/Protein Kinase B (PI3K/Akt) pathway. Additionally, we suggest that AT1 activation plays a role in AT2 upregulation, probably as a protective mechanism. Altogether, these effects might contribute to preserving endothelial function against the harmful effects by lead in the vascular system.

Sweet dreams: therapeutic insights, targeting imaging and physiologic evidence linking sleep, melatonin and diabetic nephropathy

Melatonin is the main biochronologic molecular mediator of circadian rhythm and sleep. It is also a powerful antioxidant and has roles in other physiologic pathways. Melatonin deficiency is associated with metabolic derangements including glucose and cholesterol dysregulation, hypertension, disordered sleep and even cancer, likely due to altered immunity. Diabetic nephropathy (DN) is a key microvascular complication of both type 1 and 2 diabetes. DN is the end result of a complex combination of metabolic, haemodynamic, oxidative and inflammatory factors. Interestingly, these same factors have been linked to melatonin deficiency. This report will collate in a clinician-oriented fashion the mechanistic link between melatonin deficiency and factors contributing to DN.

Influence of exercise training on diabetic kidney disease: A brief physiological approach

IMPACT STATEMENT

Diabetic kidney disease (DKD) is associated with increased mortality in diabetic patients and has a negative impact on public health. The identification of potential therapies that help the management of DKD can contribute to the improvement of health and quality of life of patients. Thus, this paper is timely and relevant because, in addition to presenting a concise review of the pathogenesis and major pathophysiological mechanisms of DKD, it addresses the most recent findings on the impact of exercise training on this disease. Thus, since non-pharmacological interventions have gained increasing attention in the fight against chronic diseases, this paper appears as an important tool to increase knowledge and stimulate innovative research on the impact of exercise on kidney disease.

Trade-off expression of melatonin receptor subtypes (Mel1a and Mel1b) and androgen receptor in lung of a tropical bird, Perdicula asiatica

The role of circulatory steroid hormone along with melatonin in lung of any seasonally breeding bird has never been explored so far. This could be interesting because steroid hormones are immunosuppressive while melatonin is immunostimulatory in nature. In our present study, we report the effect of exogenous melatonin and testosterone on expression of melatonin receptor subtypes (Mel_1a and Mel_1b ) and androgen receptor in lung of a tropical bird Perdicula asiatica. Birds were collected from vicinity of Varanasi and acclimatized in laboratory with sufficient food and water. The birds were treated with melatonin and testosterone at dose of 25 µg/100 g B.wt./day and 1 mg/100 g B.wt./day, respectively, for 28 days. At the end of the experiment, the birds were sacrificed and lung tissue and blood sample were collected for immunohistochemistry, Western blot analysis and hormonal assay. Testosterone treatment increased circulatory testosterone and upregulated expression of androgen receptors whereas downregulated expression of melatonin receptor subtypes Mel_1a and Mel_1b . Melatonin administration increased peripheral melatonin and upregulated expression of melatonin receptor subtypes Mel_1a and Mel_1b while downregulated androgen receptor. Thus, our results suggest that a trade-off relationship between melatonin and testosterone exists in regulation of their receptors in lung of Perdicula asiatica.

Repeat exposure to polyinosinic:polycytidylic acid induces TLR3 expression via JAK-STAT signaling and synergistically potentiates NFκB-RelA signaling in ARPE-19 cells

Dry age-related macular degeneration (AMD), accounting for approximately 90% of AMD cases, is characterized by photoreceptor death, retinal pigment epithelium (RPE) dysfunction and, ultimately, geographic atrophy - the localized death of RPE leading to loss of the center of the visual field. The pathological etiology of AMD is multifactorial, but innate immune signaling and inflammation are involved in early stages of the disease. Although numerous single-nucleotide polymorphisms in innate immune genes are associated with dry AMD, no single gene appears to cause dry AMD. Here, we hypothesized that activation of TLR3 potentiates expression of TLR3 itself and the NFκB-p65 (RelA) subunit as part of pro-inflammatory RPE signaling. Furthermore, we hypothesized that TLR3 activation can 'prime' cells to future RelA stimulation, leading to enhanced, persistent RelA expression and signaling following a second TLR3 activation. We used the human RPE-derived cell line ARPE-19 as a model system for RPE signaling and measured NFκB expression and activity in response to TLR3 stimulation with its ligand, polyinosinic:polycytidylic acid (pI:C). Activation of TLR3 with pI:C led to increased TLR3 and RelA expression that was sustained for at least 24 h. Cells exposed for a second time to pI:C after an initial pI:C exposure displayed elevated RelA expression and RelA nuclear translocation above the level generated by individual primary or secondary exposures alone. Such an elevated response could also not be generated by a single application of higher concentrations of the agonist pI:C. Additionally, we determined the mechanism for TLR3 mediated TLR3 and RelA expression by using inhibitors of canonical TLR3-TBK1-IKKε and JAK-STAT signaling pathways. These data suggest that initial exposure of ARPE-19 cells to pI:C upregulates TLR3 and RelA signaling, leading to potentiated and persistent RelA signaling potentially generated by a positive feedback loop that may cause exacerbated inflammation in AMD. Furthermore, inhibition of JAK-STAT signaling may be a possible therapeutic treatment to prevent induction of TLR3 expression subsequent to pI:C exposure. Our results identify possible therapeutic targets to reduce the TLR3 positive feedback loop and subsequent overproduction of pro-inflammatory cytokines in RPE cells.

The pivotal role of melatonin in ameliorating chronic kidney disease by suppression of the renin-angiotensin system in the kidney

Melatonin is a hormone produced by the pineal gland, predominantly at night, and plays a pivotal role in regulating the circadian rhythm as well as a variety of biological functions, including anti-inflammation, anti-oxidation, inhibition of sympathetic nerve activity, and preservation of endothelial cell function. The intrarenal renin-angiotensin system (RAS) is one of the most important contributors in the pathophysiology of chronic kidney disease (CKD) and hypertension, independent of the circulating RAS, due to sodium reabsorption and inflammation and fibrosis in the kidney. However, the relationship between melatonin secretion and intrarenal RAS activation has remained unknown. It has been recently shown that impaired nighttime melatonin secretion is associated with nighttime urinary angiotensinogen excretion, a surrogate marker of intrarenal RAS activation and renal damage in patients with CKD. Moreover, it has also been indicated that melatonin administered exogenously exercises antioxidant effects that ameliorate intrarenal RAS activation and renal injury in chronic progressive CKD animal models. As a result, the new roles of melatonin in suppressing RAS in the kidney via amelioration of reactive oxygen species have been clarified. Therefore, we review the relationship between melatonin and intrarenal RAS activation and indicate the possibility of a new strategy to suppress CKD, which is a risk factor for cardiovascular and end-stage renal diseases.

Anti-Inflammatory Effects of Melatonin in Obesity and Hypertension

PURPOSE OF REVIEW

Here, we review the known relations between hypertension and obesity to inflammation and postulate the endogenous protective effect of melatonin and its potential as a therapeutic agent. We will describe the multiple effects of melatonin on blood pressure, adiposity, body weight, and focus on mitochondrial-related anti-inflammatory and antioxidant protective effects.

RECENT FINDINGS

Hypertension and obesity are usually associated with systemic and tissular inflammation. The progressive affection of target-organs involves multiple mediators of inflammation, most of them redundant, which make anti-inflammatory strategies ineffective. Melatonin reduces blood pressure, body weight, and inflammation. The mechanisms of action of this ancient molecule of protection involve multiple levels of action, from subcellular to intercellular. Mitochondria is a key inflammatory element in vascular and adipose tissue and a potential pharmacological target. Melatonin protects against mitochondrial dysfunction. Melatonin reduces blood pressure and adipose tissue dysfunction by multiple anti-inflammatory/antioxidant actions and provides potent protection against mitochondria-mediated injury in hypertension and obesity. This inexpensive and multitarget molecule has great therapeutic potential against both epidemic diseases.

Histomorphological changes in the pancreas and kidney and histopathological changes in the liver in male Wistar rats on antiretroviral therapy and melatonin treatment

Combination antiretroviral therapy (cART) has shown to cause inflammation, cellular injury and oxidative stress, whereas melatonin has been successful in reducing these effects. The aim of the study was to determine potential morphometric changes caused by cART in combination with melatonin supplementation in human immunodeficiency virus (HIV)-free rats. Tissue samples (N = 40) of the pancreas, liver and kidney from a control (C/ART-/M-), cART group (C/ART + ), melatonin (C/M + ) and experimental group (ART+/M + ) were collected and stained with haematoxylin and eosin (H&E) and evaluated for histopathology. The pancreata were labelled with anti-insulin and anti-glucagon to determine α- and β-cell regions. Kidneys were stained with periodic acid Schiff (PAS) to measure the area, perimeter, diameter and radius of renal corpuscles, glomeruli and proximal convoluted tubules (PCTs). Blood tests were conducted to determine hepatotoxicity. No significant changes in histopathology were seen. Melatonin stimulated pancreatic islet abundance, as the number of islets per mm² was significantly higher in the C/M+ than in the C/ART-/M- and ART+/M+. Parameters of the renal corpuscle, glomeruli, renal space and PCTs were significantly lower in the C/ART+ compared to the other groups, thus cART may have caused tubular dysfunction or cellular damage. A significant increase in serum haemoglobin was observed in the C/ART+ compared to the C/ART-, which showed cART increases serum haemoglobin in the absence of immune deficiency. Serum lipids were significantly decreased in the C/M+ compared to the C/ART-, possibly due to the effect of melatonin on the decrease of lipolysis, decreasing effect on cholesterol absorption and stimulation of lipoprotein lipase (LPL) activity. In conclusion, we have demonstrated that melatonin stimulated α-cell production, increased the number of pancreatic islets and caused a decrease in total lipids, whereas cART increased serum haemoglobin and decreased various parameters of the nephron in an HIV-free rat model, suggestive of tubular dysfunction.

Idiopathic pulmonary fibrosis (IPF) signaling pathways and protective roles of melatonin

Idiopathic pulmonary fibrosis (IPF) is characterized by the progressive loss of lung function due to tissue scarring. A variety of pro-inflammatory and pro-fibrogenic factors including interleukin‑17A, transforming growth factor β, Wnt/β‑catenin, vascular endothelial growth factor, platelet-derived growth factor, fibroblast growth factors, endotelin‑1, renin angiotensin system and impaired caveolin‑1 function are involved in the IPF pathogenesis. Current therapies for IPF have some limitations and this highlights the need for effective therapeutic agents to treat this fatal disease. Melatonin and its metabolites are broad-spectrum antioxidants that not only remove reactive oxygen and nitrogen species by radical scavenging but also up-regulate the expression and activity of endogenous antioxidants. Via these actions, melatonin and its metabolites modulate a variety of molecular pathways in different pathophysiological conditions. Herein, we review the signaling pathways involved in the pathophysiology of IPF and the potentially protective effects of melatonin on these pathways.

Previous Exercise Training Reduces Markers of Renal Oxidative Stress and Inflammation in Streptozotocin-Induced Diabetic Female Rats

The aim of this study is to evaluate the effects of regular moderate exercise training initiated previously or after induction of diabetes mellitus on renal oxidative stress and inflammation in STZ-induced diabetic female rats. For this purpose, Wistar rats were divided into five groups: sedentary control (SC), trained control (TC), sedentary diabetic (SD), trained diabetic (TD), and previously trained diabetic (PTD). Only the PTD group was submitted to treadmill running for 4 weeks previously to DM induction with streptozotocin (40 mg/kg, i.v). After confirming diabetes, the PTD, TD, and TC groups were submitted to eight weeks of exercise training. At the end of the training protocol, we evaluated the following: glycosuria, body weight gain, plasma, renal and urinary levels of nitric oxide and thiobarbituric acid reactive substances, renal glutathione, and immunolocalization of lymphocytes, macrophages, and nuclear factor-kappa B (NF-κB/p65) in the renal cortex. The results showed that exercise training reduced glycosuria, renal TBARS levels, and the number of immune cells in the renal tissue of the TD and PTD groups. Of note, only previous exercise increased weight gain and urinary/renal NO levels and reduced NF-κB (p65) immunostaining in the renal cortex of the PTD group. In conclusion, our study shows that exercise training, especially when initiated previously to diabetes induction, promotes protective effects in diabetic kidney by reduction of renal oxidative stress and inflammation markers in female Wistar rats.

Melatonin ameliorates intrarenal renin-angiotensin system in a 5/6 nephrectomy rat model

BACKGROUND

Activation of the intrarenal renin-angiotensin system (RAS) plays a critical role in the pathophysiology of chronic kidney disease (CKD) and hypertension. It has been reported that reactive oxygen species (ROS) are important components of intrarenal RAS activation. Melatonin is recognized as a powerful antioxidant, and we recently reported that impaired nighttime melatonin secretion correlates negatively with urinary angiotensinogen excretion, the surrogate marker of intrarenal RAS activity in patients with CKD. However, whether melatonin supplementation ameliorates the augmentation of intrarenal RAS in CKD has remained unknown. We aimed to clarify whether exogenous melatonin ameliorates intrarenal RAS activation via the reduction of ROS production.

METHODS

5/6 Nephrectomized (Nx) rats were used as a chronic progressive CKD model and compared with sham-operated control rats. The Nx rats were divided into untreated Nx rats and melatonin-treated Nx rats. The levels of intrarenal RAS, ROS components, and renal injury were evaluated after 4 weeks of treatment.

RESULTS

Compared with the control rats, the untreated Nx rats exhibited significant increases in intrarenal angiotensinogen, angiotensin II (AngII) type 1 receptors, and AngII, accompanied by elevated blood pressure, higher oxidative stress (8-hydroxy-2'-deoxyguanosine), lower antioxidant (superoxide dismutase) activity, and increased markers of interstitial fibrosis (α-smooth muscle actin, Snail, and type I collagen) in the remnant kidneys. Treatment with melatonin significantly reversed these abnormalities.

CONCLUSION

Antioxidant treatment with melatonin was shown to ameliorate intrarenal RAS activation and renal injury in a 5/6 Nx rat model.

Salt, Hypertension, and Immunity

The link between inappropriate salt retention in the kidney and hypertension is well recognized. However, growing evidence suggests that the immune system can play surprising roles in sodium homeostasis, such that the study of inflammatory cells and their secreted effectors has provided important insights into salt sensitivity. As part of the innate immune system, myeloid cells have diverse roles in blood pressure regulation, ranging from prohypertensive actions in the kidney, vasculature, and brain, to effects in the skin that attenuate blood pressure elevation. In parallel, T lymphocyte subsets, as key constituents of the adaptive immune compartment, have variable effects on renal sodium handling and the hypertensive response, accruing from the functions of the cytokines that they produce. Conversely, salt can directly modulate the phenotypes of myeloid and T cells, illustrating bidirectional regulatory mechanisms through which sodium and the immune system coordinately impact blood pressure. This review details the complex interplay between myeloid cells, T cells, and salt in the pathogenesis of essential hypertension.

BCL6 attenuates renal inflammation via negative regulation of NLRP3 transcription

Renal inflammation contributes to the pathogeneses of hypertension. This study was designed to determine whether B-cell lymphoma 6 (BCL6) attenuates renal NLRP3 inflammasome activation and inflammation and its underlying mechanism. Male spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were used in the present study. Angiotensin (Ang) II or lipopolysaccharides (LPS) was used to induce inflammation in HK-2 cells, a human renal tubular epithelial (RTE) cell line. NLRP3 inflammasome was activated and BCL6 was downregulated in the kidneys of SHR. Either Ang II or LPS suppressed BCL6 expression in HK-2 cells. BCL6 overexpression in HK-2 cells attenuated Ang II-induced NLRP3 upregulation, inflammation and cell injury. The inhibitory effects of BCL6 overexpression on NLRP3 expression and inflammation were also observed in LPS-treated HK-2 cells. BCL6 inhibited the NLRP3 transcription via binding to the NLRP3 promoter. BCL6 knockdown with shRNA increased NLRP3 and mature IL-1β expression levels in both PBS- or Ang II-treated HK-2 cells but had no significant effects on ASC, pro-caspase-1 and pro-IL-1β expression levels. BCL6 overexpression caused by recombinant lentivirus expressing BCL6 reduced blood pressure in SHR. BCL6 overexpression prevented the upregulation of NLRP3 and mature IL-1β expression levels in the renal cortex of SHR. The results indicate that BCL6 attenuates Ang II- or LPS-induced inflammation in HK-2 cells via negative regulation of NLRP3 transcription. BCL6 overexpression in SHR reduced blood pressure, NLRP3 expression and inflammation in the renal cortex of SHR.

Role of the Immune System in Hypertension

High blood pressure is present in more than one billion adults worldwide and is the most important modifiable risk factor of death resulting from cardiovascular disease. While many factors contribute to the pathogenesis of hypertension, a role of the immune system has been firmly established by a large number of investigations from many laboratories around the world. Immunosuppressive drugs and inhibition of individual cytokines prevent or ameliorate experimental hypertension, and studies in genetically-modified mouse strains have demonstrated that lymphocytes are necessary participants in the development of hypertension and in hypertensive organ injury. Furthermore, immune reactivity may be the driving force of hypertension in autoimmune diseases. Infiltration of immune cells, oxidative stress, and stimulation of the intrarenal angiotensin system are induced by activation of the innate and adaptive immunity. High blood pressure results from the combined effects of inflammation-induced impairment in the pressure natriuresis relationship, dysfunctional vascular relaxation, and overactivity of the sympathetic nervous system. Imbalances between proinflammatory effector responses and anti-inflammatory responses of regulatory T cells to a large extent determine the severity of inflammation. Experimental and human studies have uncovered autoantigens (isoketal-modified proteins and heat shock protein 70) of potential clinical relevance. Further investigations on the immune reactivity in hypertension may result in the identification of new strategies for the treatment of the disease.

Melatonin: Protection against age-related cardiac pathology

Aging is a complex and progressive process that involves physiological and metabolic deterioration in every organ and system. Cardiovascular diseases are one of the most common causes of mortality and morbidity among elderly subjects worldwide. Most age-related cardiovascular disorders can be influenced by modifiable behaviours such as a healthy diet rich in fruit and vegetables, avoidance of smoking, increased physical activity and reduced stress. The role of diet in prevention of various disorders is a well-established factor, which has an even more important role in the geriatric population. Melatonin, an indoleamine with multiple actions including antioxidant properties, has been identified in a very large number of plant species, including edible plant products and medical herbs. Among products where melatonin has been identified include wine, olive oil, tomato, beer, and others. Interestingly, consumed melatonin in plant foods or melatonin supplementation may promote health benefits by virtue of its multiple properties and it may counteract pathological conditions also related to cardiovascular disorders, carcinogenesis, neurological diseases and aging. In the present review, we summarized melatonin effects against age-related cardiac alterations and abnormalities with a special focus on heart ischemia/reperfusion (IR) injury and myocardial infarction.

Can melatonin prevent or improve metabolic side effects during antipsychotic treatments?

In the last two decades, second-generation antipsychotics (SGAs) were more frequently used than typical antipsychotics for treating both psychotic and nonpsychotic psychiatric disorders in both children and adolescents, because of their lower risk of adverse neurological effects, that is, extrapyramidal symptoms. Recent studies have pointed out their effect on weight gain and increased visceral adiposity as they induce metabolic syndrome. Patients receiving SGAs often need to be treated with other substances to counteract metabolic side effects. In this paper, we point out the possible protective effect of add-on melatonin treatment in preventing, mitigating, or even reversing SGAs metabolic effects, improving quality of life and providing safer long-term treatments in pediatric patients. Melatonin is an endogenous indolamine secreted during darkness by the pineal gland; it plays a key role in regulating the circadian rhythm, generated by the suprachiasmatic nuclei (SCN) of the hypothalamus, and has many other biological functions, including chronobiotic, antioxidant and neuroprotective properties, anti-inflammatory and free radical scavenging effects, and diminishing oxidative injury and fat distribution. It has been hypothesized that SGAs cause adverse metabolic effects that may be restored by nightly administration of melatonin because of its influence on autonomic and hormonal outputs. Interestingly, atypical anti-psychotics (AAPs) can cause several sleep disorders, and circadian misalignment can influence hormones involved in the metabolic regulation, such as insulin, leptin, and ghrelin; furthermore, a relationship between obesity and sleep curtailment has been demonstrated, as well as sleep deprivation in rats has been associated with hyperphagia. Metabolic effects of melatonin, both central and peripheral, direct and indirect, target most metabolic disorders reported during and after SGA treatment in children, adolescents, and adults. Further systematic studies on psychiatric patients are needed to explore the effect of add-on melatonin on metabolic side effects of SGAs, independent of energy intake, diet, and exercise.

Does the Interdependence between Oxidative Stress and Inflammation Explain the Antioxidant Paradox?

Oxidative stress has been implicated in many chronic diseases. However, antioxidant trials are so far largely unsuccessful as a preventive or curative measure. Chronic low-grade inflammatory process, on the other hand, plays a central role in the pathogenesis of a number of chronic diseases. Oxidative stress and inflammation are closely related pathophysiological processes, one of which can be easily induced by another. Thus, both processes are simultaneously found in many pathological conditions. Therefore, the failure of antioxidant trials might result from failure to select appropriate agents that specifically target both inflammation and oxidative stress or failure to use both antioxidants and anti-inflammatory agents simultaneously or use of nonselective agents that block some of the oxidative and/or inflammatory pathways but exaggerate the others. To examine whether the interdependence between oxidative stress and inflammation can explain the antioxidant paradox we discussed in the present review the basic aspects of oxidative stress and inflammation and their relationship and dependence.

Melatonin prevents kidney injury in a high salt diet-induced hypertension model by decreasing oxidative stress

Melatonin, a potent antioxidant molecule, plays a role in blood pressure regulation. We hypothesized that melatonin may generate a protective effect in a high salt diet (HSD) rodent model mediated by decreasing renal oxidative stress. Dahl salt-sensitive rats were divided into three groups according to diet: normal chow (control); HSD; HSD with melatonin [30/mg/kg/day]) placed in their water (HSD + Mel) over an 8-wk period. Blood pressure was measured by the tail cuff method. Kidney injury was evaluated by 24 H urine protein excretion. Glomerular injury index (GII) (fibrotic glomeruli/100 glomeruli) was evaluated from a Masson's trichrome-stained section. Kidney oxidative stress was determined by superoxide production via dihydroethidium staining. Expression of oxidative stress-related genes was measured by reverse transcriptase-qPCR. Melatonin had no effect on blood pressure increase induced by HSD and attenuated proteinuria induced by HSD (HSD--50.7 ± 12, HSD + Mel--22.3 ± 4.3, controls--6.5 ± 1.0 gram protein/gram creatinine, P < 0.001). HSD-induced glomerular damage was significantly diminished by melatonin (GII in HSD--24 ± 6, HSD + Mel--3.6 ± 0.8, controls--0.8 ± 0.5, P < 0.05). Superoxide production was significantly higher in kidneys of HSD fed rats than the controls (99 ± 9 versus 60 ± 7 relative fluorescent units (RFU)/μm(2), respectively, P < 0.05). Melatonin also decreased superoxide production (74 ± 5 RFU/μm(2), P < 0.05). The expression of kidney inducible nitric oxide synthase and p67(phox) mRNA was significantly higher in HSD than in the controls and HSD + Mel rats. Treatment with melatonin eliminated the deleterious effect of HSD in the kidneys of Dahl salt-sensitive rats. The beneficial effect of melatonin is not mediated by lowering blood pressure but by a direct antioxidative effect.

Melatonin attenuates hypertension-induced renal injury partially through inhibiting oxidative stress in rats

The aim of the present study was to investigate the protective effects of melatonin (MLT) on hypertension-induced renal injury and identify its mechanism of action. Twenty-four healthy male Wistar rats were divided into a sham control group (n=8), which was subjected to sham operation and received vehicle treatment (physiological saline intraperitoneally at 0.1 ml/100 g), a vehicle group (n=8), which was subjected to occlusion of the left renal artery and vehicle treatment, and the MLT group (n=8), which was subjected to occlusion of the left renal artery and treated with MLT (10 mg/kg/day). Pathological features of the renal tissues were determined using hematoxylin and eosin staining and Masson staining. Urine protein, serum creatinine (Scr), superoxide dismutase (SOD) and malondialdehyde (MDA) were determined. Immunohistochemical analysis was performed to determine the expression of heme oxygenase-1 (HO-1), intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS). Furthermore, reverse transcription polymerase chain reaction was conducted to determine the mRNA expression of HO-1, ICAM-1, eNOS and iNOS. A marked decrease in blood pressure was noticed in the MLT group at week 4 compared with that of the vehicle group (P<0.01). Furthermore, MLT treatment attenuated the infiltration of inflammatory cells and oedema/atrophy of renal tubules. MLT attenuated hypertension-induced increases in urine protein excretion, serum creatinine and MDA as well as decreases in SOD activity in renal tissues. Furthermore, MLT attenuated hypertension-induced increases in iNOS and ICAM-1 as well as decreases in eNOS and HO-1 expression at the mRNA and protein level. In conclusion, the results of the present study indicated that MLT had protective roles in hypertension-induced renal injury. Its mechanism of action is, at least in part, associated with the inhibition of oxidative stress.

Cofilin1 is involved in hypertension-induced renal damage via the regulation of NF-κB in renal tubular epithelial cells

BACKGROUND

Inflammation mediated by nuclear factor-κB (NF-κB) plays a critical role in the pathogenesis of hypertensive nephropathy (HN). Cytoskeletal remodelling is necessary for the activation of NF-κB. An actin-binding protein, cofilin-1 promotes dynamic alterations to the cytoskeleton by severing actin filaments. However, whether cofilin1 modulates NF-κB activity via cytoskeletal remodelling in the setting of hypertensive renal damage and what mechanisms underlie this phenomenon, remain unknown.

METHODS

Twenty-one-week old spontaneously hypertensive rats (SHRs) were treated with an antioxidant (100 or 250 mg kg(-1) day(-1)), grape seed proanthocyanidins extract (GSPE), for 22 weeks. Twenty-four-hour urinary protein, serum creatinine and urea nitrogen levels were measured. Haematoxylin and eosin (HE) staining was performed, and the expression levels of renal cortex cofilin1, monocyte chemotactic protein 1 (MCP1), interleukin-1β (IL1β) and NF-κB were evaluated via either Western blotting or immunohistochemistry. In vitro, human proximal renal tubular epithelial cells (HK-2 cells) were pre-incubated either with or without GSPE and subsequently treated with angiotensinII (AngII). Furthermore, a lentiviral shRNA-vector was utilized to knockdown cofilin1 expression in the HK-2 cells, which were stimulated with AngII. Actin filaments, NF-κB activity and several downstream inflammatory factors, including MCP1 and IL-1β, were investigated.

RESULTS

In addition to elevated blood pressure and 24 h urinary protein levels, NF-κB activity and the expression levels of MCP1 and IL-1β were significantly increased, resulting in tubulointerstitial inflammatory infiltration in SHRs. The phosphorylation (inactivation) of cofilin1 was increased in the kidneys of the SHRs. In vitro, AngII stimulation resulted in the phosphorylation of cofilin1, the formation of actin stress fibres and nuclear translocation of NF-κB p65 in the HK2 cells. Both GSPE pretreatment and the shRNA knockdown of cofilin1 inhibited Rel/p65 nuclear translocation, as well as the expression of both MCP-1 and IL-1β in the AngII-induced HK2 cells.

CONCLUSION

These results demonstrate that cofilin1 is involved in hypertensive nephropathy by modulating the nuclear translocation of NF-κB and the expression of its downstream inflammatory factors in renal tubular epithelial cells.

Prevention of nephrotoxicity induced by cyclosporine-A: role of antioxidants

Cyclosporine A (CsA) is a powerful immunosuppressive drug used to prevent allograft rejection after organ transplantation as well as in human and veterinary medicine. Unfortunately, its use is hampered by its nephrotoxic effects. The mechanisms of CsA-induced hypertension and nephrotoxicity are not clear, but several studies suggest the possible involvement of free radicals. In this review we have summarized the effect of some antioxidants that we have used in the recent years, in combination with CsA, to better understand the exact mechanism of action of CsA and to try to open new perspectives in the treatment of CsA nephrotoxicity.

Chronic NF-κB blockade improves renal angiotensin II type 1 receptor functions and reduces blood pressure in Zucker diabetic rats

Background

Both angiotensin II type 1 receptor (AT₁R) and nuclear factor-kappa B (NF-κB) play significant roles in the pathogenesis of hypertension and type 2 diabetes. However, the role of NF-κB in perpetuating renal AT₁ receptors dysfunction remains unclear. The aim of the present study to determine whether blockade of NF-κB, could reverse the exaggerated renal AT₁R function, reduce inflammatory state and oxidative stress, lower blood pressure in Zucker diabetic fatty (ZDF) rats.

Methods

Pyrrolidine dithiocarbamate (PDTC), a NF-κB inhibitor (150 mg/kg in drinking water)or vehicle was administered orally to 12-weeks-old ZDF rats and their respective control lean Zucker (LZ) rats for 4 weeks. Blood pressure was measured weekly by tail-cuff method. AT₁R functions were determined by measuring diuretic and natriuretic responses to AT₁R antagonist (candesartan; 10 μg/kg/min iv). The mRNA and protein levels of NF-κB, oxidative stress maker and AT₁R were determined using quantitative real-time PCR and Western blotting, respectively. The NF-κB-DNA binding activity in renal cortex was measured by Electrophoretic mobility shift assay (EMSA).

Results

As compared with LZ rats, ZDF rats had higher blood pressure, impaired natriuresis and diuresis, accompanied with higher levels of oxidative stress and inflammation. Furthermore, AT₁R expression was higher in renal cortex from ZDF rats; candesartan induced natriresis and diuresis, which was augmented in ZDF rats. Treatment with PDTC lowered blood pressure and improved diuretic and natriuretic effects in ZDF rats; meanwhile, the increased oxidative stress and inflammation were reduced; the increased AT₁R expression and augmented candesartan-mediated natriuresis and diuresis were recoverd in ZDF rats. Our further study investigated the mechanisms of PDTC on AT₁R receptor expression. It resulted that PDTC inhibited NF-κB translocation from cytosol to nucleus, inhibited binding of NF-κB with AT₁R promoter, therefore, reduced AT₁R expression and function.

Conclusions

Our present study indicates blockade of NF-κB, via inhibition of binding of NF-κB with AT₁R promoter, reduces renal AT₁R expression and function, improves oxidative stress and inflammatory/anti-inflammatory balance, therefore, lowers blood pressure and recovers renal function in ZDF rats.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-015-0239-7) contains supplementary material, which is available to authorized users.

Cardioprotective effects of melatonin against myocardial injuries induced by chronic intermittent hypoxia in rats

Obstructive sleep apnea (OSA) associated with chronic intermittent hypoxia (CIH) increases the morbidity and mortality of ischemic heart disease in patients. Yet, there is a paucity of preventive measures targeting the pathogenesis of CIH-induced myocardial injury. We examined the cardioprotective effect of melatonin against the inflammation, fibrosis and the deteriorated sarcoplasmic reticulum (SR) Ca(2+) homeostasis, and ischemia/reperfusion (I/R)-induced injury exacerbated by CIH. Adult male Sprague Dawley rats that had received a daily injection of melatonin (10 mg/kg) or vehicle were exposed to CIH treatment mimicking a severe OSA condition for 4 wk. Systolic pressure, heart weights, and malondialdehyde were significantly increased in hypoxic rats but not in the melatonin-treated group, when compared with the normoxic control. Levels of the expression of inflammatory cytokines (TNF-α, IL-6, and COX-2) and fibrotic markers (PC1 and TGF-β) were significantly elevated in the hypoxic group but were normalized by melatonin. Additionally, infarct size of isolated hearts with regional I/R was substantial in the hypoxic group treated with vehicle but not in the melatonin-treated group. Moreover, melatonin treatment mitigated the SR-Ca(2+) homeostasis in the cardiomyocyte during I/R with (i) Ca(2+) overloading, (ii) decreased SR-Ca(2+) content, (iii) lowered expression and activity of Ca(2+) -handling proteins (SERCA2a and NCX1),and (iv) decreased expressions of CAMKII and phosphorylated eNOS(ser1177). Furthermore, melatonin ameliorated the level of expression of antioxidant enzymes (CAT and MnSOD) and NADPH oxidase (p22 and NOX2). Results support a prophylactic usage of melatonin in OSA patients, which protects against CIH-induced myocardial inflammation and fibrosis with impaired SR-Ca(2+) handling and exacerbated I/R injury.

Role of progesterone in melatonin-mediated protection against acute kidney injury

BACKGROUND

Melatonin is released by pineal gland and maintains circadian rhythm in the body. It has been reported as renoprotective agent because of its antioxidant property. Recently, a cross talk between progesterone and melatonin has been observed in various preclinical studies. The present study investigated the involvement of progesterone receptors in melatonin-mediated protection against ischemia reperfusion induced acute kidney injury (AKI) in rats.

MATERIALS AND METHODS

The rats were subjected to bilateral renal ischemia for 40 min followed by reperfusion for 24 h to induce AKI. The AKI was assessed by measuring creatinine clearance, serum urea, uric acid level, potassium level, fractional excretion of sodium, lactate dehydrogenase activity, and microproteinuria. The oxidative stress in renal tissues was assessed by quantification of myeloperoxidase activity, thiobarbituric acid reactive substances, superoxide anion generation, reduced glutathione level, and catalase activity. The hematoxylin-eosin staining was carried out to observe histopathologic changes in renal tissues. The melatonin (4 and 10 mg/kg, intraperitoneally) and progesterone receptor antagonist mifepristone (5 mg/kg, intraperitoneally) were used in the present study.

RESULTS

The renal ischemia reperfusion induced AKI as indicated by significant change in serum, urinary, and tissue parameters that was ameliorated by prior treatment with melatonin. No significant difference in serum progesterone level was observed between various groups used in the present study. The prior administration of mifepristone abolished melatonin-mediated protection against AKI.

CONCLUSIONS

It is concluded that melatonin treatment affords protection against ischemia reperfusion induced AKI. Moreover, progesterone receptors are essentially involved in mediating protective role of melatonin against AKI in rats.

Urine 6-sulfatoxymelatonin levels are inversely associated with arterial stiffness in post-menopausal women

OBJECT

The secretion of melatonin, a pleiotropic hormone mainly synthesized by the pineal gland, typically decreases with age and may be associated with the development of aging-related pathologic conditions such as cardiovascular disease. Atherosclerosis is an aging-related disease, the pathogenesis of which involves chronic inflammation and increased oxidative stress. Since melatonin has both anti-oxidant and anti-inflammatory properties, it may be associated with atherosclerosis. Therefore, we investigated the relationship between urine concentrations of 6-sulfatoxymelatonin (aMT6s) and arterial stiffness in post-menopausal women.

METHODS

A total of 66 post-menopausal women participated in the study. Melatonin secretion was estimated by measuring aMT6s levels in first morning urine samples. The cardio-ankle vascular index (CAVI) was used as an indicator of arterial stiffness.

RESULTS

Estimated mean CAVI decreased gradually with increasing aMT6s quartiles. The multivariate logistic regression analysis showed that the fourth aMT6s quartile was associated with a high CAVI with an adjusted odds ratio of 0.03 (95% confidence interval, 0.01-0.47).

CONCLUSION

Our study revealed an inverse relationship between urine aMT6s and arterial stiffness as determined by CAVI. Although it is impossible to determine causality, our results suggest that melatonin may have a beneficial role in the pathogenesis of atherosclerosis. Further prospective studies are required to establish the clinical significance of our study.

Genetics of melatonin receptor type 2 is associated with left ventricular function in hypertensive patients treated according to guidelines

BACKGROUND

Melatonin exerts multiple biological effects with potential impact on human diseases. This is underscored by genetic studies that demonstrated associations between melatonin receptor type 2 gene (MTNR1B) polymorphisms and characteristics of type 2 diabetes. We set out to test the hypothesis whether genetic variants at MTNR1B are also relevant for other disease phenotypes within the cardiovascular continuum. We thus investigated single nucleotide polymorphisms (SNPs) of MTNR1B in relation to blood pressure (BP) and cardiac parameters in hypertensive patients.

METHODS

Patients (n=605, mean age 56.2±9.4years, 82.3% male) with arterial hypertension and cardiac ejection fraction (EF) ≥40% were studied. Cardiac parameters were assessed by echocardiography.

RESULTS

The cohort comprised subjects with coronary heart disease (73.1%) and myocardial infarction (48.1%) with a mean EF of 63.7±8.9%. Analysis of SNPs rs10830962, rs4753426, rs12804291, rs10830963, and rs3781638 revealed two haplotypes 1 and 2 with frequencies of 0.402 and 0.277, respectively. Carriers with haplotype 1 (CTCCC) showed compared to non-carriers a higher mean 24-hour systolic BP (difference BP: 2.4mmHg, 95% confidence interval (CI): 0.3 to 4.5mmHg, p=0.023). Haplotype 2 (GCCGA) was significantly related to EF with an absolute increase of 1.8% (CI: 0.45 to 3.14%) in carriers versus non-carriers (p=0.009).

CONCLUSION

Genetics of MTNR1B point to impact of the melatonin signalling pathway for BP and left ventricular function. This may support the importance of the melatonin system as a potential therapeutic target.

Impaired pressure natriuresis is associated with interstitial inflammation in salt-sensitive hypertension

PURPOSE OF REVIEW

Impairment of the pressure natriuresis relationship is a central event in the pathogenesis of hypertension. Renal tubulointerstitial inflammation results in salt-sensitive hypertension and, until recently, the changes in pressure natriuresis induced by renal inflammation received little attention.

RECENT FINDINGS

Oxidative stress and increased intrarenal angiotensin II activity, in association with rarefaction and loss of peritubular vascular network, may be involved in the inflammation-induced blunting of the natriuresis resulting from increments in renal perfusion pressure.

SUMMARY

Here, we review the mechanisms for the impairment in pressure natriuresis resulting from renal tubulointerstitial inflammation in reference to the normal physiologic mechanisms involved in this response.

Indapamide lowers blood pressure by increasing production of epoxyeicosatrienoic acids in the kidney

Diuretics are widely used in the treatment of hypertension, although the precise mechanisms remain unknown. Epoxyeicosatrienoic acids (EETs), cytochrome P450 (P450) epoxygenase metabolites of arachidonic acid, play critical roles in regulation of blood pressure. The present study was carried out to investigate whether EETs participate in the antihypertensive effect of thiazide diuretics [hydrochlorothiazide (HCTZ)] and thiazide-like diuretics (indapamide). Male spontaneously hypertensive rats (SHRs) were treated with indapamide or HCTZ for 8 weeks. Systolic blood pressure, measured via tail-cuff plethysmography and confirmed via intra-arterial measurements, was significantly decreased in indapamide- and HCTZ-treated SHRs compared with saline-treated SHRs. Indapamide increased kidney CYP2C23 expression, decreased soluble epoxide hydrolase expression, increased urinary and renovascular 11,12- and 14,15-EETs, and decreased production of 11,12- and 14,15-dihydroxyeicosatrienoic acids in SHRs. No effect on expression of CYP4A1 or CYP2J3, or on 20-hydroxyeicosatetraenoic acid production, was observed, suggesting indapamide specifically targets CYP2C23-derived EETs. Treatment of SHRs with HCTZ did not affect the levels of P450s or their metabolites. Increased cAMP activity and protein kinase A expression were observed in the renal microvessels of indapamide-treated SHRs. Indapamide ameliorated oxidative stress and inflammation in renal cortices by down-regulating the expression of p47phox, nuclear factor-κB, transforming growth factor-β1, and phosphorylated mitogen-activated protein kinase. Furthermore, the p47phox-lowering effect of indapamide in angiotensin II-treated rat mesangial cells was partially blocked by the presence of N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MS-PPOH) or CYP2C23 small interfering RNA. Together, these results indicate that the hypotensive effects of indapamide are mediated, at least in part, by the P450 epoxygenase system in SHRs, and provide novel insights into the blood pressure-lowering mechanisms of diuretics.

Melamine activates NFκB/COX-2/PGE2 pathway and increases NADPH oxidase-dependent ROS production in macrophages and human embryonic kidney cells

Melamine is a wildly used compound in manufactures of plastics and resins. A variety of toxic effects from melamine, including nephrolithiasis, chronic kidney inflammation, and bladder carcinoma, have been mentioned. Oxidative stress is considered to be an important pathogenic mechanism of kidney disease which may develop from an increasing free radical production through inflammation. The aim of this study is to investigate melamine-induced oxidative stress and inflammation in macrophage-like cell line RAW 264.7 and human embryonic kidney cell line HEK293. Results indicated melamine activated nuclear factor (NF)-κB through increasing IκB-α degradation and NF-κB p65/p50 DNA-binding activity. In addition, melamine significantly increased COX-2 expression and prostaglandin E2 (PGE2) production. Moreover, melamine activated NADPH oxidase (NOX), including NOX1, NOX2 and NOX4, accompanied with an increase in reactive oxygen species (ROS) production. Furthermore, melamine-induced ROS production could be attenuated by apocynin, a NOX inhibitor. In conclusion, our findings suggest melamine increased inflammation and oxidative stress via activation of NF-κB/COX-2 and NOX/ROS pathway, and first revealed the critical role of NOX in melamine-induced ROS production, suggesting the potential of NOX inhibitor against melamine toxicity.

Immune reactivity to heat shock protein 70 expressed in the kidney is cause of salt-sensitive hypertension

Hypertension affects one-third of the adult population of the world. The causes of hypertension are incompletely understood, but relative impairment of sodium excretion is central to its pathogenesis. Immune cell infiltration in the kidney is a constant finding in hypertension that in association with local angiotensin and oxidants causes a defect in sodium excretion. However, it is unclear if the T cell influx into the kidney responds to nonspecific chemokine cues or is due to antigen-driven immune attraction. We found that T cells in experimentally induced salt-driven hypertension present a CD4 clonal response to heat shock protein 70 (HSP70) that is overexpressed in the kidney. We used a highly preserved amino acid sequence within the HSP molecule to induce immune tolerance associated with the generation of IL-10 producing regulatory T cells. Immune tolerant rats to HSP70 developed minimal renal inflammation and were protected from the development of salt-sensitive hypertension. Adoptive transfer of T lymphocytes isolated from spleen of tolerized rats also reversed hypertension. HSP70 gene delivery to the renal vein of the kidneys of rats sensitized to HSP70 caused an increment in blood pressure in response to a high-salt diet. The HSP70 peptide used in this work induces a strong proliferative response in peripheral blood lymphocytes of patients with essential hypertension. These studies provide evidence that autoimmunity plays a role in salt-sensitive hypertension and identifies HSP70 expressed in the kidney as one key antigen. These findings raise the possibility of novel approaches to the treatment of this condition.

Effects of melatonin on partial unilateral ureteral obstruction induced oxidative injury in rat kidney

AIM

This experimental study was designed to produce ischemia-reperfusion injury in rat kidney by performing partial unilateral ureteral obstruction (PUUO) and investigated the effects of melatonin on the levels of oxidative injury parameters.

MATERIALS AND METHODS

Twenty-four adult male rats were randomly divided into three groups as follows; control group (Group 1); only nephrectomy and blood (5 ml) drawn from vena cava inferior, PUUO group (Group 2); PUUO (10 days)+ipsilateral nephrectomy after recovery of PUUO+blood from vena cava inferior VCI, melatonin treated group (Group 3); PUUO (10 days)+melatonin (1/2 hr before release, 50 mg/kg, ip)+ipsilateral nephrectomy after recovery of PUUO+blood from VCI. The left ureter was embedded into the psoas muscle to create PUUO. After 10 days, PUUO was recovered and ipsilateral nephrectomies were performed for biochemical analysis of superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), glutathione peroxidase (GSH-Px), and protein carbonyl (PC) in the tissues and blood was drawn from inferior vena cava to study the same parameters in systemic circulation. The results were compared statistically.

RESULTS

The blood levels of MDA, NO, and PC were increased in the PUUO group in comparison to the sham-operated group (P<0.05). Melatonin treatment reduced MDA, NO, and PC levels in blood after PUUO recovery, but statistically significance consisted only for MDA and NO (P<0.05). The antioxidant enzyme activities (SOD, GSH-Px) were increased in the PUUO group (P<0.05). Melatonin treatment reduced SOD and GSH-Px activities in comparison with the sham-operated control group (P<0.05). Similarly, renal tissue levels of MDA, NO, and PC were increased in the PUUO group in comparison with the sham-operated group (P<0.05). Melatonin treatment ameliorated MDA, NO, and PC levels in renal tissue after PUUO recovery only MDA was statistically significant (P<0.05). Antioxidant enzyme activities (SOD, CAT, and GSH-Px) were increased in the PUUO group. Melatonin treatment caused reduction in SOD, CAT, and GSH-Px activities in comparison to the sham-operated control group (P<0.05).

CONCLUSION

The results of this study showed that experimentally induced PUUO caused oxidative stress in rat kidney and melatonin treatment reduced oxidative stress and therefore may have a preventive effect on PUUO induced oxidative kidney damage in rats.

Melatonin in cardiovascular disease

This editorial refers to "Cardiovascular effects of melatonin receptor agonists". The hormone melatonin is synthesized primarily in the pineal gland, retina, several peripheral tissues and organs. In the circulation, the concentration of melatonin follows a circadian rhythm, with high levels at night providing timing cues to target tissues endowed with melatonin receptors. Based on the data available, the last 18 years indicate that melatonin influences multiple factors of the cardiovascular function. Multiple evidences reveal that the rhythmicity of melatonin has a crucial role in a variety of cardiovascular pathophysiological processes including anti-inflammatory, antioxidant, anti-hypertensive and possibly as an antilipidemic function. Melatonin receptors receive and transduce melatonin's message to influence daily and seasonal rhythms of physiology. The melatonin message is translated through the interaction between the melatonin receptors (MT1 and MT2) and its coupling to G proteins, which are potential therapeutic targets in disorders ranging from insomnia, circadian sleep disorders, depression and cardiovascular diseases. Based on the data available, melatonin seems to have cardioprotective properties via its direct free radical scavenger activity. Melatonin efficiently interacts with several reactive oxygen species (receptor-independent actions). Collectively, these protective actions of melatonin may have potential clinical applicability for individuals with cardiovascular disease.

P2X7 deficiency attenuates hypertension and renal injury in deoxycorticosterone acetate-salt hypertension

The P2X(7) receptor is a ligand-gated ion channel, and genetic variations in the P2X(7) gene significantly affect blood pressure. P2X(7) receptor expression is associated with renal injury and inflammatory diseases. Uninephrectomized wild-type (WT) and P2X(7)-deficient (P2X(7) KO) mice were subcutaneously implanted with deoxycorticosterone acetate (DOCA) pellets and fed an 8% salt diet for 18 days. Their blood pressure was assessed by a telemetry system. The mice were placed in metabolic cages, and urine was collected for 24 h to assess renal function. After 18 days of DOCA-salt treatment, P2X(7) mRNA and protein expression increased in WT mice. Blood pressure in P2X(7) KO mice was less than that of WT mice (mean systolic blood pressure 133 ± 3 vs. 150 ± 2 mmHg). On day 18, urinary albumin excretion was lower in P2X(7) KO mice than in WT mice (0.11 ± 0.07 vs. 0.28 ± 0.07 mg/day). Creatinine clearance was higher in P2X(7) KO mice than in WT mice (551.53 ± 65.23 vs. 390.85 ± 32.81 μl·min(-1)·g renal weight(-1)). Moreover, renal interstitial fibrosis and infiltration of immune cells (macrophages, T cells, B cells, and leukocytes) were markedly attenuated in P2X(7) KO mice compared with WT mice. The levels of IL-1β, released by macrophages, in P2X(7) KO mice had decreased dramatically compared with that in WT mice. These results strongly suggest that the P2X(7) receptor plays a key role in the development of hypertension and renal disease via increased inflammation, indicating its potential as a novel therapeutic target.

From hypertension to stroke: mechanisms and potential prevention strategies

Stroke is a major cause of disability and death worldwide. Prevention aimed at risk factors of stroke is the most effective strategy to curb the stroke pandemic. Hypertension is one of the most important risk factors for stroke. Despite the substantial evidence of the benefits of lowering blood pressure, conventional treatment does not normalize the burden of major cardiovascular events in patients with hypertension. Fully understanding the factors involved in the hypertension-induced stroke helps to develop new strategies for stroke prevention. Antihypertensive therapies selected should have positive blood pressure-independent effects on stroke risk. This review summarizes the factors involved in the hypertension-induced stroke, such as oxidative stress, inflammation, and arterial baroreflex dysfunction, and potential strategies for its prevention, therefore, provides clues for clinicians.

Smooth muscle protein 22 alpha-Cre is expressed in myeloid cells in mice

BACKGROUND

Experiments using Cre recombinase to study smooth muscle specific functions rely on strict specificity of Cre transgene expression. Therefore, accurate determination of Cre activity is critical to the interpretation of experiments using smooth muscle specific Cre.

METHODS AND RESULTS

Two lines of smooth muscle protein 22 α-Cre (SM22α-Cre) mice were bred to floxed mice in order to define Cre transgene expression. Southern blotting demonstrated that SM22α-Cre was expressed not only in tissues abundant of smooth muscle, but also in spleen, which consists largely of immune cells including myeloid and lymphoid cells. PCR detected SM22α-Cre expression in peripheral blood and peritoneal macrophages. Analysis of SM22α-Cre mice crossed with a recombination detector GFP mouse revealed GFP expression, and hence recombination, in circulating neutrophils and monocytes by flow cytometry.

CONCLUSIONS

SM22α-Cre mediates recombination not only in smooth muscle cells, but also in myeloid cells including neutrophils, monocytes, and macrophages. Given the known contributions of myeloid cells to cardiovascular phenotypes, caution should be taken when interpreting data using SM22α-Cre mice to investigate smooth muscle specific functions. Strategies such as bone marrow transplantation may be necessary when SM22α-Cre is used to differentiate the contribution of smooth muscle cells versus myeloid cells to observed phenotypes.

Role of renal DJ-1 in the pathogenesis of hypertension associated with increased reactive oxygen species production

The D(2) dopamine receptor (D(2)R) is important in the pathogenesis of essential hypertension. We have already reported that systemic deletion of the D(2)R gene in mice results in reactive oxygen species (ROS)-dependent hypertension, suggesting that the D(2)R has antioxidant effects. However, the mechanism of this effect is unknown. DJ-1 is a protein that has antioxidant properties. D(2)R and DJ-1 are expressed in the mouse kidney and colocalize and coimunoprecipitate in mouse renal proximal tubule cells. We hypothesized that D(2)Rs regulate renal ROS production in the kidney through regulation of DJ-1 expression or function. Heterozygous D(2)(+/-) mice have increased blood pressure, urinary 8-isoprostanes, and renal Nox 4 expression, but decreased renal DJ-1 expression. Silencing D(2)R expression in mouse renal proximal tubule cells increases ROS production and decreases the expression of DJ-1. Conversely, treatment of these cells with a D(2)R agonist increases DJ-1 expression and decreases Nox 4 expression and NADPH oxidase activity, effects that are partially blocked by a D(2)R antagonist. Silencing DJ-1 expression in mouse renal proximal tubule cells increases ROS production and Nox 4 expression. Selective renal DJ-1 silencing by the subcapsular infusion of DJ-1 siRNA in mice increases blood pressure, renal Nox4 expression, and NADPH oxidase activity. These results suggest that the inhibitory effects of D(2)R on renal ROS production are at least, in part, mediated by a positive regulation of DJ-1 expression/function and that DJ-1 may have a role in the prevention of hypertension associated with increased ROS production.

Renal inflammation, autoimmunity and salt-sensitive hypertension

1. The present article reviews the role of immune-competent cells infiltrating the kidney and their association with oxidative stress and renal angiotensin activity in the development of salt-sensitive hypertension. 2. We discuss changes in the pressure-natriuresis relationship resulting from renal inflammation and its improvement resulting from immunosuppressive treatment. 3. The potential role of T-cell-driven reactivity in sustaining the renal inflammation is examined in the light of accumulating evidence of autoimmune mechanisms in experimental and clinical hypertension.

The role of oxidative stress in the developmental origin of adult hypertension

OBJECTIVE

To determine whether oxidative stress plays a role in the development of hypertension using a mouse model of fetal programming induced by endothelial nitric oxide synthase deficiency.

STUDY DESIGN

Homozygous nitric oxide synthase knockout and wild type mice were cross-bred producing maternal (endothelial nitric oxide synthase+pat/-mat) and paternal (endothelial nitric oxide synthase+mat/-pat) heterozygous offspring. RNA from liver and kidney tissues of female pups were obtained at 14 weeks of age. Relative expression of the heat shock protein-B6, peroxiredoxin-3, superoxide dismutase-1, peroxisome proliferator-activated receptor gamma, nitric oxide synthase-1 and -2 were determined.

RESULTS

In the kidneys, expression of nitric oxide synthase-2, peroxiredoxin-3, heat shock protein-B6, and superoxide dismutase-1 was up-regulated in endothelial nitric oxide synthase+pat/-mat but not in endothelial nitric oxide synthase+mat/-pat compared with wild type offspring. In the liver, there were no significant differences in the expression of nitric oxide synthase-1, nitric oxide synthase-2, peroxiredoxin, superoxide dismutase-1, or peroxisome proliferator-activated receptor gamma; however, heat shock protein-B6 was down-regulated in both heterozygotes offspring compared with wild type.

CONCLUSION

The intrauterine environment alters oxidative pathways gene expression in the kidneys of offspring, which may be a mechanism in the development of adult hypertension.