Change in central kinin B2 receptor density after exercise training in rats

Cardiovascular responses elicited by the stimulation of kinin B2 receptors in the IV cerebral ventricle paratrigeminal nucleus or in the thoracic spinal cord are similar to those observed during an exercise bout Considering that the kalikrein-kinin system (KKS) could act on the cardiovascular modulation during behavioral responses as physical exercise or stress this study evaluated the central B2 receptor densities of Wistar (W) and spontani ously hypertensive rats (SHR) after chronic moderate exercise Animals we re exercise-trained for ten weeks on a treadmill Afterwards systolic blood pressure decreased in both trained strains Animals were killed and the medulla and spinal cord extracted for B2 receptor autoradiography Trained animals were compared to their sedentary controls Sedentary groups showed specific binding sites for Hoe-140 (fmol/mg of tissue) in laminas 1 and 2 of the spinal cord nucleus of the solitary tract (NTS) area postrema (AP) spinal trigeminal tract (sp5) and paratrigeminal nucleus (Pa5) In trained W a significant increase (p<0 05) in specific binding was observed in the Pa5 (31 3%) and NTS (28 2%) Trained SHR showed a significant decrease in n ceptor density in lamina 2 (21 9%) of the thoracic spinal cord and an increase in specific binding in Pa5 (36 1%) We suggest that in the medulla chronic exercise could hyper stimulate the KKS enhancing their efficiency through the increase of B2 receptor density involving this receptor in central cardiovascular control during exercise or stress In the lamina 2 B2 receptor might be involved in the exercise-induced hypotension (C) 2010 Elsevier BV All rights reserved

Brabykinin B1 Receptor Antagonism Is Beneficial in Renal Ischemia-Reperfusion Injury

Previously we have demonstrated that bradykinin B1 receptor deficient mice (B1KO) were protected against renal ischemia and reperfusion injury (IRI). Here, we aimed to analyze the effect of B1 antagonism on renal IRI and to study whether B1R knockout or antagonism could modulate the renal expression of pro and anti-inflammatory molecules. To this end, mice were subjected to 45 minutes ischemia and reperfused at 4, 24, 48 and 120 hours. Wild-type mice were treated intra-peritoneally with antagonists of either B1 (R-954, 200 mg/kg) or B2 receptor (HOE140, 200 mg/kg) 30 minutes prior to ischemia. Blood samples were collected to ascertain serum creatinine level, and kidneys were harvested for gene transcript analyses by real-time PCR. Herein, B1R antagonism ( R-954) was able to decrease serum creatinine levels, whereas B2R antagonism had no effect. The protection seen under B1R deletion or antagonism was associated with an increased expression of GATA-3, IL-4 and IL-10 and a decreased T-bet and IL-1b transcription. Moreover, treatment with R-954 resulted in lower MCP-1, and higher HO-1 expression. Our results demonstrated that bradykinin B1R antagonism is beneficial in renal IRI.

Role of kinin B1 and B2 receptors in memory consolidation during the aging process of mice

Under physiological conditions, elderly people present memory deficit associated with neuronal loss. This pattern is also associated with Alzheimer`s disease but, in this case, in a dramatically intensified level. Kinin receptors have been involved in neurodegeneration and increase of amyloid-beta concentration, associated with Alzheimer`s disease (AD). Considering these findings, this work evaluated the role of kinin receptors in memory consolidation during the aging process. Male C57BI/6 (wt), knock-out B1 (koB1) or B2 (koB2) mice (3, 6, 12 and 18-month-old - mo; n = 10 per group) were submitted to an acquisition session, reinforcement to learning (24 h later: test 1) and final test (7 days later: test 2), in an active avoidance apparatus, to evaluate memory. Conditioned avoidance responses (CAR, % of 50 trials) were registered. In acquisition sessions, similar CAR were obtained among age matched animals from all strains. However, a significant decrease in CAR was observed throughout the aging process (3mo: 8.8 +/- 2.3%; 6mo: 4.1 +/- 0.6%; 12mo: 2.2 +/- 0.6%, 18mo: 3.6 +/- 0.6%, P < 0.01), indicating a reduction in the learning process. In test 1, as expected, memory retention increased significantly (P < 0.05) in all 3- and 6-month-old animals as well as in 12-month-old-wt and 12-month-old-koB1 (P < 0.01), compared to the training session. However, 12-month-old-koB2 and all 18-month-old animals did not show an increase in memory retention. In test 2, 3- and 6-month-old wt and koB1 mice of all ages showed a significant improvement in memory (P < 0.05) compared to test 1. However, 12-month-old wt and koB2 mice of all ages showed no difference in memory retention. We suggest that, during the aging process, the B1 receptor could be involved in neurodegeneration and memory loss. Nevertheless, the B2 receptor is apparently acting as a neuroprotective factor. (C) 2009 Elsevier Ltd. All rights reserved.

Participation of kinin receptors on memory impairment after chronic infusion of human amyloid-beta 1-40 peptide in mice

Chronic infusion of human amyloid-beta 1-40 (A beta) in the lateral ventricle (LV) of rats is associated with memory impairment and increase of kinin receptors in cortical and hippocampal areas. Deletion of kinin B1 or B2 receptors abolished memory impairment caused by an acute single injection of A beta in the LV. As brain tissue and kinin receptors could unlikely react to acute or chronic administration of a similar quantity of A beta, we evaluated the participation of B1 or B2 receptors in memory impairment after chronic infusion of A beta. Male C57BI/6 J (wt), knock-out B1 (koB1) or B2 (koB2) mice (12 weeks of age) previously trained in a two-way shuttle-box and achieving conditioned avoidance responses (CAR, % of 50 trials) were infused with AB (550 pmol, 0.12 mu L/h, 28 days) or vehicle in the LV using a mini-osmotic pump. They were tested before the surgery (TO), 7 and 35 days after the infusion started (T7; T35). In T0, no difference was observed between CAR of the control (Cwt = 59.7 +/- 6.7%; CkoB1 = 46.7 +/- 4.0%; CkoB2 = 64.4 +/- 5.8%) and A beta (A beta wt = 66.0 +/- 3.0%; A beta koB1 = 66.8 +/- 8.2%; A beta koB2 = 58.7 +/- 5.9%) groups. In T7, A beta koB2 showed a significant decrease in CAR (41.0 +/- 8.6%) compared to the control-koB2 (72.8 +/- 2.2%, P <0.05). In T35, a significant decrease (P <0.05) was observed in A beta wt (40.7 +/- 3.3%) and A beta koB2 (41.2 +/- 10.7%) but not in the A beta koB1 (64.0 +/- 14.0%) compared to their control groups. No changes were observed in the controls at T35. We suggest that in chronic infusion of BA, B1 receptors could playan important role in the neurodegenerative process. Conversely, the premature memory impairment of koB2 suggests that it may be a protective factor. (C) 2009 Elsevier Ltd. All rights reserved.

Kallikrein-Kinin System Mediated Inflammation in Alzheimer`s Disease In Vivo

The Kallikrein-Kinin System (KKS) has been associated to inflammatory and immunogenic responses in the peripheral and central nervous system by the activation of two receptors, namely B1 receptor and B2 receptor. The B1 receptor is absent or under-expressed in physiological conditions, being up-regulated during tissue injury or in the presence of cytokines. The B2 receptor is constitutive and mediates most of the biological effects of kinins. Some authors suggest a link between the KKS and the neuroinflammation in Alzheimer`s disease (AD). We have recently described an increase in bradykinin (BK) in the cerebrospinal fluid and in densities of B1 and B2 receptors in brain areas related to memory, after chronic infusion of amyloid-beta (A beta) peptide in rats, which was accompanied by memory disruption and neuronal loss. Mice lacking B1 or B2 receptors presented reduced cognitive deficits related to the learning process, after acute intracerebroventricular (i.c.v). administration of A. Nevertheless, our group showed an early disruption of cognitive function by i.c.v. chronic infusion of A beta after a learned task, in the knock-out B2 mice. This suggests a neuroprotective role for B2 receptors. In knock-out B1 mice the memory disruption was absent, implying the participation of this receptor in neurodegenerative processes. The acute or chronic infusion of A beta can lead to different responses of the brain tissue. In this way, the proper involvement of KKS on neuroinflammation in AD probably depends on the amount of A beta injected. Though, BK applied to neurons can exert inflammatory effects, whereas in glial cells, BK can have a potential protective role for neurons, by inhibiting proinflammatory cytokines. This review discusses this duality concerning the KKS and neuroinflammation in AD in vivo.

Insertion/deletion polymorphism of the bradykinin type 2 receptor gene influence diastolic blood pressure

The contribution of kinins to the beneficial effects in cardiovascular risk reductions remains unclear. In this context, the present study examined whether the +9bp/-9 bp polymorphism in bradykinin type 2 receptor gene, predicts hypertension risk in a large urban Brazilian population. Our finding indicated that the -9 bp allele may contribute to hypertension because of increased diastolic pressure.

Enalapril treatment corrects the reduced response to bradykinin in diabetes increasing the B2 protein expression

Considering the growing importance of the interaction between components of kallikreinkinin and renin-angiotensin systems in physiological and pathological processes, particularly in diabetes mellitus, the aim of the present study was to investigate the effect of enalapril on the reduced response of bradykinin and on the interaction between angiotensin-(1-7) (Ang-(1-7)) and bradykinin (BK), important components of these systems, in an insulin-resistance model of diabetes. For the above purpose, the response of mesenteric arterioles of anesthetized neonatal streptozotocin-induced (n-STZ) diabetic and control rats was evaluated using intravital microscopy. In n-STZ diabetic rats, enalapril treatment restored the reduced response to BK but not the potentiation of BK by Ang-(1-7) present in non-diabetic rats. The restorative effect of enalapril was observed at a dose that did not correct the altered parameters induced by diabetes such as hyperglycernia, glicosuria, insulin resistance but did reduce the high blood pressure levels of n-SZT diabetic rats. There was no difference in mRNA and protein expressions of B1 and B2 kinin receptor subtypes between n-STZ diabetic and control rats. Enalapril treatment increased the B2 kinin receptor expression. From our data, we conclude that in diabetes enalapril corrects the impaired BK response probably by increasing the expression of B2 receptors. The lack of potentiation of BK by Ang-(1-7) is not corrected by this agent. (c) 2008 Elsevier Inc. All rights reserved.

Bradykinin receptor 1 activation exacerbates experimental focal and segmental glomerulosclerosis

Focal and segmental glomerulosclerosis (FSGS) is one of the most important causes of end-stage renal failure. The bradykinin B1 receptor has been associated with tissue inflammation and renal fibrosis. To test for a role of the bradykinin B1 receptor in podocyte injury, we pharmacologically modulated its activity at different time points in an adriamycin-induced mouse model of FSGS. Estimated albuminuria and urinary protein to creatinine ratios correlated with podocytopathy. Adriamycin injection led to loss of body weight, proteinuria, and upregulation of B1 receptor mRNA. Early treatment with a B1 antagonist reduced albuminuria and glomerulosclerosis, and inhibited the adriamycin-induced downregulation of podocin, nephrin, and alpha-actinin-4 expression. Moreover, delayed treatment with antagonist also induced podocyte protection. Conversely, a B1 agonist aggravated renal dysfunction and even further suppressed the levels of podocyte-related molecules. Thus, we propose that kinin has a crucial role in the pathogenesis of FSGS operating through bradykinin B1 receptor signaling. Kidney International (2011) 79, 1217-1227; doi:10.1038/ki.2011.14; published online 16 March 2011

Influência do bloqueador de receptor de angiotensina (Losartana potássica) na função renal e pressão arterial em cães GRMD

A distrofia muscular de Duchenne (DMD) é uma alteração neuromuscular caracterizada por contínua necrose muscular e degeneração, com eventual fibrose e infiltração por tecido adiposo. O aumento progressivo da fibrose intersticial no músculo impede a migração das células miogênicas, necessárias para a formação muscular. O modelo canino constitui-se nas melhores fenocópias da doença em humanos, quando comparados com outros modelos animais com distrofia. O tratamento antifibrose de pacientes DMD, tendo como alvo os mediadores da citocina, TGF-beta, e o tratamento com antiinflamatórios, podem limitar a degeneração muscular e contribuir para a melhora do curso da doença. O presente estudo teve como objetivo observar os possíveis efeitos adversos na fisiologia renal, por meio de avaliação bioquímica sanguínea e da pressão arterial, verificando a viabilidade do uso do Losartan (um inibidor de TGF-beta) nos cães afetados pela distrofia muscular. Foram utilizados quatro cães adultos, sendo dois machos e duas fêmeas. Utilizou-se a dose de 50mg de Losartan, administrada via oral, uma vez ao dia. Os exames clínicos, bem como alterações na função renal, o nível do potássio sérico e a pressão arterial não evidenciaram reação adversa durante todo o período do experimento. O uso de Losartan, por um período de 9 semanas, mostrou-se como uma terapia segura para o tratamento antifibrótico em cães adultos, não afetando a função renal ou pressão arterial dos animais.

AT1-receptor mediated vascular damage in myocardium, kidneys and liver in rats

The systemic aspect of vascular damage induced by angiotensin II (ANG II) has been poorly explored in the literature. Considering the presence of ANG II and its specific receptor AT1, in several organs, all tissues might be potentially affected by its effects. The aims of this study were: To evaluate the early histological changes in the heart, liver and kidneys, produced by ANG II infusion, to evaluate the protective effect of losartan. Wistar rats were distributed into three groups: control (no treatment), treated with ANG II, and treated with ANG II + losartan. ANG II was continuously infused over 72 hours by subcutaneous osmotic pumps. Histological sections of the myocardium, kidneys and liver were stained and observed for the presence of necrosis. There were ANG II-induced perivascular inflammation and necrosis of the arteriolar wall in the myocardium, kidney, and liver by, which were partially prevented by losartan. There was no significant correlation between heart and kidney damage. Tissue lesion severity was lower than that of vascular lesions, without statistical difference between groups. ANG II causes vascular injury in the heart, kidneys and liver, indicating a systemic vasculotoxic effect; the mechanisms of damage/protection vary depending on the target organ; perivascular lesions may occur even when anti-hypertensive doses of losartan are used.

Toll-like receptor 4 (TLR4) expression in human and murine pancreatic beta-cells affects cell viability and insulin homeostasis

Background: Toll-like receptor 4 (TLR4) is widely recognized as an essential element in the triggering of innate immunity, binding pathogen-associated molecules such as Lipopolysaccharide (LPS), and in initiating a cascade of pro-inflammatory events. Evidence for TLR4 expression in non-immune cells, including pancreatic beta-cells, has been shown, but, the functional role of TLR4 in the physiology of human pancreatic beta-cells is still to be clearly established. We investigated whether TLR4 is present in beta-cells purified from freshly isolated human islets and confirmed the results using MIN6 mouse insulinoma cells, by analyzing the effects of TLR4 expression on cell viability and insulin homeostasis. Results: CD11b positive macrophages were practically absent from isolated human islets obtained from nondiabetic brain-dead donors, and TLR4 mRNA and cell surface expression were restricted to beta-cells. A significant loss of cell viability was observed in these beta-cells indicating a possible relationship with TLR4 expression. Monitoring gene expression in beta-cells exposed for 48h to the prototypical TLR4 ligand LPS showed a concentration-dependent increase in TLR4 and CD14 transcripts and decreased insulin content and secretion. TLR4-positive MIN6 cells were also LPS-responsive, increasing TLR4 and CD14 mRNA levels and decreasing cell viability and insulin content. Conclusions: Taken together, our data indicate a novel function for TLR4 as a molecule capable of altering homeostasis of pancreatic beta-cells.

Interleukin-22 forms dimers that are recognized by two interleukin-22R1 receptor chains

Interleukin-22 (IL-22) is a class 2 cytokine whose primary structure is similar to that of interleukin 10 (IL-10) and interferon-gamma (IFN-gamma). IL-22 induction during acute phase immune response indicates its involvement in mechanisms of inflammation. Structurally different from IL-10 and a number of other members of IL-10 family, which form intertwined inseparable V-shaped dimers of two identical polypeptide chains, a single polypeptide chain of IL-22 folds on itself in a relatively globular structure. Here we present evidence, based on native gel electrophoresis, glutaraldehyde cross-linking, dynamic light scattering, and small angle x-ray scattering experiments, that human IL-22 forms dimers and tetramers in solution under protein concentrations assessable by these experiments. Unexpectedly, low-resolution molecular shape of IL-22 dimers is strikingly similar to that of IL-10 and other intertwined cytokine dimeric forms. Furthermore, we determine an ab initio molecular shape of the IL-22/IL-22R1 complex which reveals the V-shaped IL-22 dimer interacting with two cognate IL-22R1 molecules. Based on this collective evidence, we argue that dimerization might be a common mechanism of all class 2 cytokines for the molecular recognition with their respective membrane receptor. We also speculate that the IL-22 tetramer formation could represent a way to store the cytokine in nonactive form at high concentrations that could be readily converted into functionally active monomers and dimers upon interaction with the cognate cellular receptors.

Structural basis of GC-1 selectivity for thyroid hormone receptor isoforms

Background: Thyroid receptors, TRa and TR beta, are involved in important physiological functions such as metabolism, cholesterol level and heart activities. Whereas metabolism increase and cholesterol level lowering could be achieved by TR beta isoform activation, TRa activation affects heart rates. Therefore, beta-selective thyromimetics have been developed as promising drug-candidates for treatment of obesity and elevated cholesterol level. GC-1 [ 3,5-dimethyl-4-(4'-hydroxy- 3'-isopropylbenzyl)-phenoxy acetic acid] has ability to lower LDL cholesterol with 600-to 1400-fold more potency and approximately two-to threefold more efficacy than atorvastatin (Lipitor(C)) in studies in rats, mice and monkeys. Results: To investigate GC-1 specificity, we solved crystal structures and performed molecular dynamics simulations of both isoforms complexed with GC-1. Crystal structures reveal that, in TRa Arg228 is observed in multiple conformations, an effect triggered by the differences in the interactions between GC-1 and Ser277 or the corresponding asparagine (Asn331) of TR beta. The corresponding Arg282 of TR beta is observed in only one single stable conformation, interacting effectively with the ligand. Molecular dynamics support this model: our simulations show that the multiple conformations can be observed for the Arg228 in TR alpha, in which the ligand interacts either strongly with the ligand or with the Ser277 residue. In contrast, a single stable Arg282 conformation is observed for TR beta, in which it strongly interacts with both GC-1 and the Asn331. Conclusion: Our analysis suggests that the key factors for GC-1 selectivity are the presence of an oxyacetic acid ester oxygen and the absence of the amino group relative to T(3). These results shed light into the beta-selectivity of GC-1 and may assist the development of new compounds with potential as drug candidates to the treatment of hypercholesterolemia and obesity.

Association of alpha1a-adrenergic receptor polymorphism and blood pressure phenotypes in the Brazilian population

Background: The alpha1A-adrenergic receptor (alpha(1A)-AR) regulates the cardiac and peripheral vascular system through sympathetic activation. Due to its important role in the regulation of vascular tone and blood pressure, we aimed to investigate the association between the Arg347Cys polymorphism in the alpha(1A)-AR gene and blood pressure phenotypes, in a large sample of Brazilians from an urban population. Methods: A total of 1568 individuals were randomly selected from the general population of the Vitoria City metropolitan area. Genetic analysis of the Arg347Cys polymorphism was conducted by polymerase chain reaction/restriction fragment length polymorphism. We have compared cardiovascular risk variables and genotypes using ANOVA, and Chi-square test for univariate comparisons and logistic regression for multivariate comparisons. Results: Association analysis indicated a significant difference between genotype groups with respect to diastolic blood pressure (p = 0.04), but not systolic blood pressure (p = 0.12). In addition, presence of the Cys/Cys genotype was marginally associated with hypertension in our population (p = 0.06). Significant interaction effects were observed between the studied genetic variant, age and physical activity. Presence of the Cys/Cys genotype was associated with hypertension only in individuals with regular physical activity (odds ratio = 1.86; p = 0.03) or younger than 45 years (odds ratio = 1.27; p = 0.04). Conclusion: Physical activity and age may potentially play a role by disclosing the effects of the Cys allele on blood pressure. According to our data it is possible that the Arg347Cys polymorphism can be used as a biomarker to disease risk in a selected group of individuals.