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Kinins B1 and B2 receptors (B1R and B2R) are classically associated with inflammation, but our group has recently demonstrated new roles for B1R in metabolism using a knockout model (B1−/−). B1−/− mice display improvement on leptin and insulin sensitivity and is protected from high fat diet (HFD)-induced obesity. Here, we evaluate the hepatic effects of the B1R ablation and its role on hepatic function. Despite no expression of hepatic B1R, HFD-induced hepatic lipid accumulation was lower than in control animals. B1−/− mice also presented lower hepatic lipogenesis and SCD1 protein content in the liver. When stimulated with exogenous leptin, B1−/− mice exhibited increased hepatic pJAK2. Similarly, leptin signaling was enhanced in the liver of ob/ob–B1−/− mice, as demonstrated by increased levels of pSTAT3 compared to ob/ob. Plasma concentrations of intercellular adhesion molecule 1, fetuin A, leukemia inhibitory factor, tissue inhibitor of metalloprotease-1, resistin, and oncostatin M were reduced in B1−/−. Finally, B1−/− mice have increased gene expression of hepatic B2 receptor, but no difference in leptin receptor expression. Our results show that B1−/− mice are protected from non-alcoholic fatty liver disease (NAFLD) after HFD treatment. Since B1R expression was not observed in the liver after HFD, we propose that the cross talk between the adipose tissue and the liver, mainly through leptin, is an important factor contributing to the observed results. Besides that, several other inflammatory mediators already correlated with NAFLD or liver function were found to be altered in our model. Taken together, our data suggest that B1R plays an important role in hepatic steatosis development.

Background The malaria burden remains a major public health concern, especially in sub-Saharan Africa. The complex biology of Plasmodium, the apicomplexan parasite responsible for this disease, challenges efforts to develop new strategies to control the disease. Proteolysis is a fundamental process in the metabolism of malaria parasites, but roles for proteases in generating vasoactive peptides have not previously been explored. Results In the present work, it was demonstrated by mass spectrometry analysis that Plasmodium parasites (Plasmodium chabaudi and Plasmodium falciparum) internalize and process plasma kininogen, thereby releasing vasoactive kinins (Lys-BK, BK and des-Arg9-BK) that may mediate haemodynamic alterations during acute malaria. In addition, it was demonstrated that the P. falciparum cysteine proteases falcipain-2 and falcipain-3 generated kinins after incubation with human kininogen, suggesting that these enzymes have an important role in this process. The biologic activity of peptides released by Plasmodium parasites was observed by measuring ileum contraction and activation of kinin receptors (B1 and B2) in HUVEC cells; the peptides elicited an increase in intracellular calcium, measured by Fluo-3 AM fluorescence. This effect was suppressed by the specific receptor antagonists Des-Arg9[Leu8]-BK and HOE-140. Conclusions In previously undescribed means of modulating host physiology, it was demonstrated that malaria parasites can generate active kinins by proteolysis of plasma kininogen.

Kinins B1 and B2 receptors (B1R and B2R) are classically associated with inflammation, but our group has recently demonstrated new roles for B1R in metabolism using a knockout model (B1 (-/-)). B1 (-/-) mice display improvement on leptin and insulin sensitivity and is protected from high fat diet (HFD)-induced obesity. Here, we evaluate the hepatic effects of the B1R ablation and its role on hepatic function. Despite no expression of hepatic B1R, HFD-induced hepatic lipid accumulation was lower than in control animals. B1 (-/-) mice also presented lower hepatic lipogenesis and SCD1 protein content in the liver. When stimulated with exogenous leptin, B1 (-/-) mice exhibited increased hepatic pJAK2. Similarly, leptin signaling was enhanced in the liver of ob/ob-B1 (-/-) mice, as demonstrated by increased levels of pSTAT3 compared to ob/ob. Plasma concentrations of intercellular adhesion molecule 1, fetuin A, leukemia inhibitory factor, tissue inhibitor of metalloprotease-1, resistin, and oncostatin M were reduced in B1 (-/-). Finally, B1 (-/-) mice have increased gene expression of hepatic B2 receptor, but no difference in leptin receptor expression. Our results show that B1 (-/-) mice are protected from non-alcoholic fatty liver disease (NAFLD) after HFD treatment. Since B1R expression was not observed in the liver after HFD, we propose that the cross talk between the adipose tissue and the liver, mainly through leptin, is an important factor contributing to the observed results. Besides that, several other inflammatory mediators already correlated with NAFLD or liver function were found to be altered in our model. Taken together, our data suggest that B1R plays an important role in hepatic steatosis development.

BACKGROUND: Kinins participate in the pathophysiology of obesity and type 2 diabetes by mechanisms which are not fully understood. Kinin B(1) receptor knockout mice (B(1) (-/-)) are leaner and exhibit improved insulin sensitivity. METHODOLOGY/PRINCIPAL FINDINGS: Here we show that kinin B(1) receptors in adipocytes play a role in controlling whole body insulin action and glucose homeostasis. Adipocytes isolated from mouse white adipose tissue (WAT) constitutively express kinin B(1) receptors. In these cells, treatment with the B(1) receptor agonist des-Arg(9)-bradykinin improved insulin signaling, GLUT4 translocation, and glucose uptake. Adipocytes from B(1) (-/-) mice showed reduced GLUT4 expression and impaired glucose uptake at both basal and insulin-stimulated states. To investigate the consequences of these phenomena to whole body metabolism, we generated mice where the expression of the kinin B(1) receptor was limited to cells of the adipose tissue (aP2-B(1)/B(1) (-/-)). Similarly to B(1) (-/-) mice, aP2-B(1)/B(1) (-/-) mice were leaner than wild type controls. However, exclusive expression of the kinin B(1) receptor in adipose tissue completely rescued the improved systemic insulin sensitivity phenotype of B(1) (-/-) mice. Adipose tissue gene expression analysis also revealed that genes involved in insulin signaling were significantly affected by the presence of the kinin B(1) receptor in adipose tissue. In agreement, GLUT4 expression and glucose uptake were increased in fat tissue of aP2-B(1)/B(1) (-/-) when compared to B(1) (-/-) mice. When subjected to high fat diet, aP2-B(1)/B(1) (-/-) mice gained more weight than B(1) (-/-) littermates, becoming as obese as the wild types. CONCLUSIONS/SIGNIFICANCE: Thus, kinin B(1) receptor participates in the modulation of insulin action in adipocytes, contributing to systemic insulin sensitivity and predisposition to obesity.

Background Kinins are released during dermal injury and inflammation and seem to contribute to the pathogenesis of cutaneous diseases. Objective Participation of kinins in skin inflammatory process was evaluated using knockout mice and non-peptide kinin receptor antagonists. Methods Chronic skin inflammation was induced by multiple applications of TPA in mice ear. Results The B 2 knockout mice (B 2 −/− ) showed a significant increase of ear weight (23±10%) and epidermal cellular hyperproliferation and acanthosis formation upon histological analysis when compared with wildtype mice. Also, evaluation of PCNA levels by Western blot and immunohistochemistry confirmed the increase in the epidermis hyperproliferation in the ear skin of B 2 −/− mice. In contrast, no modification in these parameters was detected in B 1 knockout mice (B 1 −/− ). However, mice lacking both kinin receptors (B 1 B 2 −/− ) presented a considerable reduction of epidermis thickness and in PCNA levels. Following the establishment of skin inflammation (5th day of TPA application) treatment with the non-peptide antagonists SSR 240612 (B 1 receptor antagonist), FR 173657 (B 2 receptor antagonist), or SSR 240612 plus FR 173657 topically applied, caused a significant inhibition of ear weight (20±5%, 34±4% and 32±6%, respectively). In the histological analysis, the antagonists produced a reduction in epidermal hyperplasia and acanthosis formation; but the treatment with a combination of the two antagonists did not increase efficacy. Conclusion Kinin receptors seem to be involved in the control of the keratinocyte hyperproliferative process, and non-peptide kinin receptor antagonists may be useful tools in the treatment of hyperproliferative skin disorders.

Kinin B1 receptor is involved in chronic inflammation and expressed in human atherosclerotic lesions. However, its significance for lesion development is unknown. Therefore, we investigated the effect of kinin B1 receptor deletion on the development of atherosclerosis and aortic aneurysms in apolipoprotein E-deficient (ApoE(-/-)) mice. Mice deficient both in ApoE and in kinin B1 receptor (ApoE(-/-)-B(1)(-/-)) were generated and analyzed for their susceptibility to atherosclerosis and aneurysm development under cholesterol rich-diet (western diet) and angiotensin II infusion. Kinin B1 receptor messenger RNA (mRNA) expression was significantly increased in ApoE(-/-) mice after Western-type diet. Although no difference in serum cholesterol was found between ApoE(-/-)-B(1)(-/-) and ApoE(-/-) mice under Western-type diet, aortic lesion incidence was significantly higher in ApoE(-/-)-B(1)(-/-) after this treatment. In accordance, we observed increased endothelial dysfunction in these mice. The mRNA expression of cyclic guanosine monophosphate-dependent protein kinase I, CD-11, F4/80, macrophage colony-stimulating factor, and tumor necrosis factor-alpha were increased in the aorta of double-deficient mice following Western-type diet, whereas the levels of peroxisome proliferator-activated receptor gamma protein and the activity of matrix metalloproteinase-9 activity were decreased. In addition to the increased atherosclerotic lesions, the lack of kinin B(1) receptor also increased the incidence of abdominal aortic aneurysms after angiotensin II infusion. In conclusion, our results show that kinin B(1) receptor deficiency aggravates atherosclerosis and aortic aneurysms under cholesterolemic conditions, supporting an antiatherogenic role for the kinin B(1) receptor.

OBJECTIVE-Kinins mediate pathophysiological processes related to hypertension, pain, and inflammation through the activation of two G-protein-coupled receptors, named B(1) and B(2). Although these peptides have been related to glucose homeostasis, their effects on energy balance are still unknown.RESEARCH DESIGN and METHODS-Using genetic and pharmacological strategies to abrogate the kinin B(1) receptor in different animal models of obesity, here we present evidence of a novel role for kinins in the regulation of satiety and adiposity.RESULTS-Kinin B(1) receptor deficiency in mice (B(1)(-/-)) resulted in less fat content, hypoleptinemia, increased leptin sensitivity, and robust protection against high-fat diet-induced weight gain. Under high-fat diet, B(1)(-/-) also exhibited reduced food intake, improved lipid oxidation, and increased energy expenditure. Surprisingly, B(1) receptor deficiency was not able to decrease food intake and adiposity in obese mice lacking leptin (ob/ob-B(1)(-/-)). However, ob/ob-B(1)(-/-) mice were more responsive to the effects of exogenous leptin on body weight and food intake, suggesting that B(1) receptors may be dependent on leptin to display their metabolic roles. Finally, inhibition of weight gain and food intake by B(1) receptor ablation was pharmacologically confirmed by long-term administration of the kinin B(1) receptor antagonist SSR240612 to mice under high-fat diet.CONCLUSIONS-Our data suggest that kinin B(1) receptors participate in the regulation of the energy balance via a mechanism that could involve the modulation of leptin sensitivity. Universidade Federal de São Paulo, Dept Biophys, BR-04023062 São Paulo, Brazil Univ Mogi das Cruzes, Mogi Das Cruzes, Brazil Universidade Federal de São Paulo, Dept Physiol, BR-04023062 São Paulo, Brazil Sanofi Aventis, Montpellier, France Universidade Federal de São Paulo, Dept Med, BR-04023062 São Paulo, Brazil Inst Natl Sante & Rech Med, Dept Renal & Cardiac Remodeling, U858 I2MR, Toulouse, France Univ Toulouse 3, Inst Med Mol Rangueil, F-31062 Toulouse, France Inst Natl Rech Agron AgroParisTech, UMR914 Nutr Physiol & Ingest Behav, Paris, France Max Delbruck Ctr Mol Med, Berlin, Germany Universidade Federal de São Paulo, Dept Biophys, BR-04023062 São Paulo, Brazil Universidade Federal de São Paulo, Dept Physiol, BR-04023062 São Paulo, Brazil Universidade Federal de São Paulo, Dept Med, BR-04023062 São Paulo, Brazil Web of Science