Inhibition of both NOX and TNF-α exerts substantial renoprotective effects in renal ischemia reperfusion injury rat model.

BACKGROUND AND AIMS: Acute kidney injury (AKI) due to renal ischemia-reperfusion injury (RIRI) is associated with high morbidity and mortality, with no renoprotective drug available. Previous research focused on single drug targets, yet this approach has not reached translational success. Given the complexity of this condition, we aimed to identify a disease module and apply a multitarget network pharmacology approach. METHODS: Identification of a disease module with potential drug targets was performed utilizing Disease Module Detection algorithm using NADPH oxidases (NOXs) as seeds. We then assessed the protective effect of a multitarget network pharmacology targeting the identified module in a rat model of RIRI. Rats were divided into five groups; sham, RIRI, and RIRI treated with setanaxib (NOX inhibitor, 10 mg/kg), etanercept (TNF-α inhibitor, 10 mg/kg), and setanaxib and etanercept (5 mg/kg each). Kidney functions, histopathological changes and oxidative stress markers (MDA and reduced GSH) were assessed. Immunohistochemistry of inflammatory (TNF-α, NF-κB) apoptotic (cCasp-3, Bax/Bcl 2), fibrotic (α-SMA) and proteolysis (MMP-9) markers was performed. RESULTS: Our in-silico analysis yielded a disease module with TNF receptor 1 (TNFR1A) as the closest target to both NOX1 and NOX2. Targeting this module by a low-dose combination of setanaxib, and etanercept, resulted in a synergistic effect and ameliorated ischemic AKI in rats. This was evidenced by improved kidney function and reduced expression of inflammatory, apoptotic, proteolytic and fibrotic markers. CONCLUSIONS: Our findings show that applying a multitarget network pharmacology approach allows synergistic renoprotective effect in ischemic AKI and might pave the way towards translational success.

Adrenergic receptors blockade alleviates dexamethasone-induced neurotoxicity in adult male Wistar rats: Distinct effects on ß-arrestin2 expression and molecular markers of neural injury.

BACKGROUND: Dexamethasone-induced neurotoxicity has been previously reported. However, the molecular mechanisms are still not completely understood. OBJECTIVES: The current work aimed to investigate the modulatory effects of α- and ß-adrenergic receptors on dexamethasone-induced neurotoxicity in rats focused on changes in ß-arrestin2 and molecular markers of neural injury in cerebral cortex. METHODS: Male Wistar rats were subcutaneously injected with dexamethasone (10 mg/kg/day) for 7 days to induce neural injury in the cerebral cortex. The experiment involved 5 groups: control, dexamethasone, carvedilol, propranolol, and doxazosin. In the last 3 groups, drugs were given 2 hours before dexamethasone injection. At the end of experiment, brain samples were collected for measurement of brain derived neurotrophic factor (BDNF), glial fibrillary acidic protein (GFAP), kinase activity of protein kinase B (Akt), diacylglycerol (DAG), α-smooth muscle actin (α-SMA), Smad3, ß-amyloid and phospho-tau protein levels in addition to histopathological examination of brain tissue using hematoxylin-eosin, Nissl, and Sirius red stains. Moreover, ß-arrestin2 levels in the cerebral cortex were measured using immunohistochemical examination. RESULTS: Dexamethasone slightly reduced brain weight and significantly decreased BDNF, Akt kinase activity and ß-arrestin2 but markedly induced degeneration of cortical neurons and significantly increased GFAP, DAG, α-SMA, Smad3, ß-amyloid and phospho-tau protein levels compared to controls. Carvedilol, propranolol, and doxazosin reversed all dexamethasone-induced molecular changes and slightly ameliorated the histopathological changes. Carvedilol significantly increased brain weight and ß-arrestin2 levels compared to dexamethasone, propranolol, and doxazosin groups. CONCLUSION: blocking α- and/or ß-adrenergic receptors alleviate dexamethasone-induced neurotoxicity despite their distinct effects on ß-arrestin2 levels in the cerebral cortex.

Hepatic ß-arrestins: potential roles in liver health and disease.

Β-arrestins are intracellular scaffolding proteins that have multifaceted roles in different types of disorders. In this review article, we gave a summary about the discovery, characterization and classification of these proteins and their intracellular functions. Moreover, this review article focused on the hepatic expression of ß-arrestins and their hepatocellular distribution and function in each liver cell type. Also, we showed that ß-arrestins are key regulators of distinct types of hepatic disorders. On the other hand, we addressed some important points that have never been studied before regarding the role of ß-arrestins in certain types of hepatic disorders which needs more research efforts to cover.

Carvedilol ameliorates dexamethasone-induced myocardial injury in rats independent of its action on the α1-adrenergic receptor.

The current study aimed to investigate the cardiotoxic effect of dexamethasone-high-dose in rats, the therapeutic effect of carvedilol and the role of α1-adrenergic receptor (α1AR). The experiment involved 6 groups: control, dexamethasone (10 mg/kg), carvedilol (10 mg/kg), phenylephrine (1 mg/kg), phenylephrine plus carvedilol and propranolol (30 mg/kg). Drugs and vehicles were given for 7 days. Dexamethasone was given with the drugs in the last 4 groups. On the 8th-day and after overnight fasting, serum and cardiac samples were collected. Serum levels of cardiac troponin I and creatine kinase-myoglobin as well as cardiac levels of diacylglycerol, malondialdehyde, kinase activity of Akt, transforming growth factor-ß, Smad3 and alpha smooth muscle actin were measured. Cardiac samples were also used for histopathological examination using hematoxylin-eosin and Sirius red stains, in addition to immunohistochemical examination using ß-arrestin2 antibody. Dexamethasone induced cardiac injury via increasing oxidative stress, apoptosis and profibrotic signals. Carvedilol significantly reduced the dexamethasone-induced cardiotoxicity. Using phenylephrine, a competitive α1-agonist, with carvedilol potentiated the cardioprotective actions of carvedilol. Propranolol, a ß-blocker without activity on α1ARs, showed higher cardiac protection than carvedilol. Dexamethasone-high-dose upregulates cardiac oxidative stress, apoptotic and profibrotic signals and induces cardiac injury. Blocking the α1-adrenergic receptor by carvedilol attenuates its cardioprotective effects against dexamethasone-induced cardiotoxicity.

Mitigation of dexamethasone-induced nephrotoxicity by modulating the activity of adrenergic receptors: Implication of Wnt/ß-arrestin2/ß-catenin pathway.

The present study aimed to investigate the role of α and ß-adrenergic receptors (ßARs) in mediation or modulation of the dexamethasone-induced nephrotoxicity by using different pharmacological interventions. Nephrotoxicity was induced by subcutaneous injection of dexamethasone (10 mg/kg) for 7 days in Wistar albino rats. Eight groups were used: control; dexamethasone; carvedilol; phenylephrine; carvedilol and phenylephrine; propranolol; doxazosin; propranolol and doxazosin. At the end of experiment, rats were euthanized and blood, urine and kidney samples were collected. Serum and urinary creatinine and urinary total protein levels were measured. Also, the renal tissue levels of diacylglycerol (DAG); Akt kinase activity, malondialdehyde (MDA), NADPH oxidase 2 (NOX2), transforming growth factor-ß (TGF-ß), Wnt3A and ß-catenin were recorded. Furthermore, histopathological and ß-arrestin2-immunohistochemical examinations of renal tissues were performed. Results: Dexamethasone induced glomerular damage, proteinuria, renal oxidative stress and upregulated the renal Wnt/ß-arrestin2/ß-catenin pathway and the profibrotic signals. Blocking the α1 and ßARs by carvedilol reduced the dexamethasone-induced nephrotoxicity. Pre-injection of phenylephrine did not reduce the reno-protective action of carvedilol. Blocking the ßARs only by propranolol reduced the dexamethasone-induced nephrotoxicity to the same extent of carvedilol group. Blocking the α1ARs only by doxazosin reduced dexamethasone-induced nephrotoxicity to a higher extent than other treatments. However, combined use of propranolol and doxazosin did not synergize the reno-protective effects of doxazosin. Conclusion: Dexamethasone induces nephrotoxicity, possibly, by upregulating the Wnt/ß-arrestin2/ß-catenin pathway. Blocking either α1ARs or ßARs can effectively protect against the dexamethasone-induced nephrotoxicity. However, combined blocking of α1ARs and ßARs does not synergize the reno-protective effects.

Acute and chronic metabolic effects of carvedilol in high-fructose, high-fat diet-fed mice: implication of ß-arrestin2 pathway.

We aimed to investigate the acute and chronic effects of carvedilol on insulin resistance in high-fructose, high-fat diet (HFrHFD) - fed mice and the implication of the ß-arrestin2 pathway. The acute effect of carvedilol (10 mg/kg, i.p.) on glucose tolerance and hepatic lipid signaling in normal and insulin resistant mice was investigated. Then, the chronic effect of carvedilol on insulin resistance and dyslipidemia in HFrHFD-fed mice was examined. Changes in ß-arrestin2 and its downstream signals in liver, skeletal muscle, and adipose tissue were measured. This involved measuring phosphatidylinositol 4,5-bisphosphate (PIP2) and diacylglycerol (DAG) levels and protein kinase B (AKT) activity. Carvedilol acutely reduced fasting blood glucose levels in both normal and insulin resistant mice without significantly affecting the glucose tolerance. These acute effects were associated with increased hepatic PIP2 but decreased hepatic DAG levels. Chronic administration of carvedilol significantly ameliorated insulin resistance and dyslipidemia in HFrHFD-fed mice. These chronic effects were associated with increased ß-arrestin2, PIP2, and AKT activity levels but decreased DAG levels in the classical insulin target tissues. In conclusion, carvedilol acutely maintains glucose homeostasis and chronically ameliorates insulin resistance and dyslipidemia in HFrHFD-fed mice. The insulin sensitizing effects of carvedilol are highly correlated with the upregulation of ß-arrestin2 pathway.

Propranolol and low-dose isoproterenol ameliorate insulin resistance, enhance ß-arrestin2 signaling, and reduce cardiac remodeling in high-fructose, high-fat diet-fed mice: Comparative study with metformin.

AIMS: ß-Arrestin2 signaling has emerged as a promising therapeutic target for the management of insulin resistance and related complications. Moreover, recent studies have shown that certain G protein-coupled receptor (GPCR) ligands can modulate ß-arrestin2 signaling. The current study examined the effects of the ß-blocker propranolol and a low dose of the agonist isoproterenol (L-D-ISOPROT) on ß-arrestin2 signaling, insulin resistance, and cardiac remodeling in high-fructose, high-fat diet (HFrHFD)-fed mice. In addition, the effects of these agents were compared to those of the clinical antidiabetic agent, metformin. MATERIALS AND METHODS: Insulin resistance was induced by HFrHFD feeding for 16 weeks. Mice were then randomly allocated to groups receiving propranolol, L-D-ISOPROT, metformin, or vehicle (control) for 4 weeks starting on week 13 of HFrHFD feeding. Survival rate, body weight, visceral fat weight, blood glucose, serum insulin, insulin resistance index, hepatic ß-arrestin2 signaling, heart weight, left and right ventricular thicknesses, cardiac fibrosis severity, serum endothelin-1, cardiac cardiotrophin-1, and cardiac ß-arrestin2 signaling were then compared among groups. KEY FINDINGS: HFrHFD for 16 weeks significantly increased insulin resistance index, cardiac fibrosis area, and serum endothelin-1, and reduced hepatic ß-arrestin2 signaling, cardiac cardiotrophin-1, and cardiac ß-arrestin2 signaling without significant changes in survival rate, body weight, visceral fat weight, heart weight, or left and right ventricular thicknesses. All three drugs reduced insulin resistance and cardiac remodeling parameters and enhanced ß-arrestin2 signaling with variable efficacies. SIGNIFICANCE: Propranolol and L-D-ISOPROT, like metformin, can reduce insulin-resistance and cardiac remodeling in HFrHFD-fed mice, possibly by upregulating ß-arrestin2 signaling activity. Therefore, ß-arrestin2-signaling modulation might be a promising strategy for insulin-resistance treatment.

Quercetin and lithium chloride potentiate the protective effects of carvedilol against renal ischemia-reperfusion injury in high-fructose, high-fat diet-fed Swiss albino mice independent of renal lipid signaling.

Renal ischemia-reperfusion injury (R-IRI) is the main cause of acute renal failure. Carvedilol has been shown to protect against R-IRI. However, the underlying mechanisms are still not completely clarified. This study aimed to investigate the role of lipid signaling in mediating carvedilol protective effects against R-IRI in insulin-resistant mice by using two different lipid signaling modulators, quercetin and lithium chloride (LiCl). Mice were fed high-fructose, high-fat diet (HFrHFD) for 16 weeks to induce insulin resistance. At the end of feeding period, mice were randomly distributed into five groups; Sham, R-IRI, Carvedilol (20 mg/kg, i.p.), Carvedilol + Quercetin (10 mg/kg, i.p.), Carvedilol + LiCl (200 mg/kg, i.p.). R-IRI was performed by applying 30 min of unilateral renal ischemia followed by one hour of reperfusion. Quercetin and LiCl were administered 30 min before carvedilol administration and carvedilol was administered 30 min before ischemia. Changes in kidney function tests, histopathology, fibrosis area, lipid signaling, inflammatory, apoptosis and oxidative stress markers in the kidney were measured. Results showed that R-IRI decreased kidney function, impaired renal tissue integrity, modulated lipid signaling and increased renal inflammation, apoptosis and oxidative stress. Carvedilol treatment decreased the detrimental effects induced by R-IRI. In addition, pre-injection of both quercetin and LiCl potentiated the reno-protective effects of carvedilol against R-IRI independent of changes in lipid mediators like phosphatidyl inositol 4,5 bisphosphate (PIP2) and diacylglycerol (DAG). In conclusion, quercetin and LiCl potentiate the protective effects of carvedilol against R-IRI in HFrHFD-fed mice by reducing inflammation and oxidative stress independent of lipid signaling.

Effect of omega-3 fatty acids on glucose homeostasis: role of free fatty acid receptor 1.

Insulin resistance is a worldwide health problem. This study investigated the acute effects of eicosapentanoic acid (EPA) on glucose homeostasis focusing on the role of free fatty acid receptor 1 (FFAR1) and the chronic effects of fish oil omega-3 fatty acids on insulin resistance. Insulin resistance was induced by feeding mice high-fructose, high-fat diet (HFrHFD) for 16 weeks. In the first part, the acute effects of EPA alone and in combination with GW1100 and DC260126 (FFAR1 blockers) on glucose homeostasis and hepatic phosphatidyl-inositol 4,5-bisphosphate (PIP2) and diacylglycerol (DAG) were investigated in standard chow diet (SCD)- and HFrHFD-fed mice. In the second part, mice were treated with fish oil omega-3 fatty acids for 4 weeks starting at the week 13 of feeding HFrHFD. Changes in the blood- and liver tissue-insulin resistance markers and FFAR1 downstream signals were recorded at the end of experiment. Results showed that EPA increased 0 and 30 min blood glucose levels after glucose load in SCD-fed mice but improved glucose tolerance in HFrHFD-fed mice. Moreover, FFAR1 blockers reduced EPA effects on glucose tolerance and hepatic PIP2 and DAG levels. On the other hand, chronic use of fish oil omega-3 fatty acids increased FBG levels and decreased serum insulin and triglycerides levels without improving the index of insulin resistance. Also, they increased hepatic ß-arrestin-2, PIP2, and pS473 Akt levels but decreased DAG levels. In conclusion, EPA acutely improved glucose homeostasis in HFrHFD-fed mice by modulating the activity of FFAR1. However, the chronic use of fish oil omega-3 fatty acids did not improve the insulin resistance.

Carvedilol Diminishes Cardiac Remodeling Induced by High-Fructose/High-Fat Diet in Mice via Enhancing Cardiac ß-Arrestin2 Signaling.

BACKGROUND: Insulin resistance (IR) is a well-known risk factor for cardiovascular complications. This study aimed to investigate the effect of a dietary model of IR in mice on cardiac remodeling, cardiac ß-arrestin2 signaling, and the protective effects of carvedilol as a ß-arrestin-biased agonist. METHODS AND RESULTS: Insulin resistance was induced by feeding mice high-fructose/high-fat diet (HFrHFD) for 16 weeks. Carvedilol was adiministered for 4 weeks starting at week 13. At the end of the experiment, body weight, heart weight, left and right ventricular thickness, visceral fat weight, fasting blood glucose (FBG), serum insulin, IR index, and serum endothelin-1 were measured. In addition, cardiac tissue samples were histopathologically examined. Also, cardiac levels of cardiotrophin-1, ß-arrestin2, phosphatidylinositol 4,5 bisphosphate (PIP2), diacylglycerol (DAG), and phosphoserine 473 Akt (pS473 Akt) were measured. Results showed significant increases in the FBG, serum insulin, IR index, serum endothelin-1, cardiac DAG, cardiac fibrosis, and degenerated cardiac myofibrils in HFrHFD-fed mice associated with a significant reduction in cardiac levels of cardiotrophin-1, ß-arrestin2, PIP2, and pS473 Akt. On the other hand, carvedilol significantly reduced the heart weight, FBG, serum insulin, IR index, serum endothelin-1, cardiac DAG, left ventricular thickness, right ventricular fibrosis, and degeneration of cardiac myofibrils. In addition, carvedilol significantly increased cardiac levels of cardiotrophin-1, ß-arrestin2, PIP2, and pS473 Akt. CONCLUSION: Carvedilol enhances cardiac ß-arrestin2 signaling and reduces cardiac remodeling in HFrHFD-fed mice.

Effect of imidazoline-1 receptor agonists on renal dysfunction in rats associated with chronic, sequential fructose and ethanol administration.

Insulin resistance and chronic alcoholism are risk factors for renal dysfunction. This study investigated the therapeutic effects of two imidazoline-1 receptor (I1R) agonists on renal dysfunction in rats after chronic, sequential fructose and ethanol administration. Daily drinking water was supplemented with fructose (10%, w/v) for 12 weeks and then with ethanol (20%, v/v) for another 8 weeks. Rats were treated with rilmenidine and clonidine in the last two weeks of the study. Blood glucose and serum insulin (sIns) levels, lipid profiles, kidney function and renal histopathology were evaluated at the end of the experiment. Additionally, renal gene expression of nischarin, phosphatidylcholine-specific phospholipase C (PC-PLC) and prostaglandin E2 (PGE2) were measured. Renal levels of superoxide dismutase (SOD), malondialdehyde (MDA), myeloperoxidase (MPO), inducible nitric oxide synthase (iNOS) and total NO (tNO) were detected, and we determined the relative renal gene expression levels of alpha smooth muscle actin (α-SMA), hydroxyproline, interleukin 10 (IL-10), tumour necrosis factor alpha (TNF-α) and caspase-3. The results showed significant deterioration of blood glucose, sIns, lipid profiles, kidney function and renal histopathology in fructose/ethanol-fed rats. Additionally, markers of inflammation, fibrosis, apoptosis and oxidative stress were upregulated. The administration of rilmenidine or clonidine significantly improved blood glucose and sIns levels and reduced renal dysfunction. Our work showed that chronic, sequential fructose and ethanol administration induced fasting hyperglycaemia and renal impairment, and these effects were ameliorated by I1R agonists.

Carvedilol protects against hepatic ischemia/reperfusion injury in high-fructose/high-fat diet-fed mice: Role of G protein-coupled receptor kinase 2 and 5.

Hepatic ischemia/reperfusion injury (H-IRI) is associated with irreversible liver damage. The current study aimed to investigate the protective effect of carvedilol against H-IRI in high-fructose high-fat diet (HFrHFD)-fed mice and the role of G protein-coupled receptor kinase 2 and 5 (GRK2 and GRK5). Mice were fed HFrHFD for 16 weeks; then mice were subjected to 30 min of ischemia followed by 1 h of reperfusion at the end of feeding period. Carvedilol (20 mg/kg, i.p.) was administered 30 min before ischemia. To explore the role of GRK2 and GRK5 in mediating carvedilol effects, paroxetine (GRK2 inhibitor, 10 mg/kg, i.p.) and amlexanox (GRK5 inhibitor, 25 mg/kg, i.p.) were administered 30 min before carvedilol administration. Liver function, histopathology and hepatic oxidative stress, as well as inflammatory and apoptotic markers were measured at the end of the experiment. In addition, adrenergic receptor downstream signals were measured in the liver. Results showed increased markers of liver injury (ALT and AST) in mice subjected to H-IRI. Moreover, liver injury was associated with slight collagen deposits as revealed by histopathology and elevated hepatic levels of oxidative stress, inflammatory and apoptotic markers. On the other hand, carvedilol protected mice against H-IRI and improved all associated pathological changes. Furthermore, pre-injection of either GRK2 or GRK5 inhibitor did not change carvedilol effects on serum ALT level and liver collagen deposits, while increased its antioxidant, anti-inflammatory and anti-apoptotic effects. In conclusion, carvedilol protects against H-IRI in HFrHFD-fed mice. GRK2 and GRK5 may not play a potential role in mediating this effect.

Hesperidin protects against stress induced gastric ulcer through regulation of peroxisome proliferator activator receptor gamma in diabetic rats.

Stress induced gastric ulcer is a serious health problem in diabetic patients. Some studies reported that hesperidin (HDN), a citrus bioflavonoid, can bind to and stimulate peroxisome proliferator-activator receptor-gamma (PPAR-γ) which may mediate its antidiabetic, anti-inflammatory and anti-oxidant effects. This work aims to study the possible protective effect of HDN against stress induced gastric ulcer in diabetic rats as well as the possible involvement of PPARγ in this effect. Type 2 diabetes was induced using streptozotocin and nicotinamide. Diabetic rats received either HDN (100 mg/kg/day, orally) & omeprazole (20 mg/kg/day, orally) or HDN (100 mg/kg/day, orally) + GW9662, PPARγ antagonist, (1 mg/kg/day, i.p.) for 8 weeks then acute gastric injury was induced by cold restraint stress technique. Glycemic controls and gastroprotective effects were evaluated by measuring serum levels of glucose and insulin, gastric free and total acidity and gastric ulcer indices. Histopathological examination of gastric mucosa was also performed. To determine the underlying mechanism of action, gastric mucosal expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), hemeoxygenase-1 (HO-1), cluster of differentiation 45 (CD45), cyclooxygenase-2 (COX-2), nuclear factor kappa B (NFκB) and inducible nitric oxide synthase (iNOS), gastric contents of reduced glutathione (GSH), malondialdehyde (MDA), tumor necrosis factor alpha (TNF-α) and nitric oxide (NO); as well as superoxide dismutase (SOD) and catalase activities were measured. HDN significantly improved glycemic level; it also reduced gastric acidity and gastric ulcer index and histopathological changes comparable to that produced by omeprazole. Moreover, HDN reduced lipid peroxidation and inflammatory markers levels and enhanced antioxidant capacity. The use of GW9662 significantly abrogated the gastric protective effect of HDN as well as reduced the antioxidant and anti-inflammatory effects. Our work showed, for the first time that, HDN has promising protective effect against stress induced gastric ulcer in diabetic rats through activation of PPARγ.

Ameliorative effects of clonidine on ethanol induced kidney injury in rats: Potential role for imidazoline-1 receptor.

Chronic alcoholism is a risk factor for kidney injury. Clonidine is an α2-adrenergic receptor/imidazoline-1 receptor agonist that can reduce blood pressure and maintain renal functions. This study aims to investigate the possible ameliorative effects of clonidine on ethanol induced kidney injury and its mechanism of action. Kidney injury was induced in rats by adding ethanol to drinking water for eight weeks. Clonidine effects on kidney functions and histopathology were measured. Moreover, phentolamine (α-adrenergic receptor antagonist), efaroxan (imidazoline-1 receptor antagonist) and rilmenidine (imidazoline-1 receptor agonist) were used to clarify the role of imidazoline-1 receptor in mediating renal ameliorative effects. Also, the effect of clonidine on liver functions and metabolic changes, in addition to renal oxidative stress, inflammatory and apoptotic pathways were measured. Results showed that, clonidine improved renal functions and reduced ethanol induced renal inflammation and fibrosis. On the other hand, efaroxan, only, blocked clonidine effects on kidney functions. Rilmenidine decreased kidney injury like clonidine. Both clonidine and rilmenidine increased renal nischarin gene expression. Furthermore, clonidine improved liver functions, increased serum insulin and decreased serum advanced glycation end products (metabolic markers). Also, clonidine reduced renal oxidative stress as reflected by decreased myeloperoxidase, malondialdehyde, inducible nitric oxide synthase and total nitric oxide levels and increased superoxide dismutase level. Moreover, clonidine reduced renal tumor necrosis factor-α (inflammatory marker) and caspase-3 (apoptotic marker) levels, while increased renal prostaglandine E2 and interleukin-10 levels (anti-inflammatory markers). In conclusion, clonidine can reduce ethanol induced kidney injury, at least in part, by stimulating imidazoline-1 receptor signaling.

Sildenafil protects against bile duct ligation induced hepatic fibrosis in rats: Potential role for silent information regulator 1 (SIRT1).

Hepatic fibrosis is a potential health problem that may end with life-threatening cirrhosis and primary liver cancer. Recent studies point out to the protective effects of silent information regulator1 (SIRT1), against different models of organs fibrosis. This work aimed to investigate the possible protective effect of sildenafil (SIRT1 activator) against hepatic fibrosis induced by bile duct ligation (BDL). Firstly, three different doses of sildenafil (5, 10, 20mg/kg/day) were investigated; to detect the most protective one against BDL induced liver dysfunction and hepatic fibrosis. The most protective dose is then used; to study its effect on BDL induced SIRT1 downregulation, imbalance of oxidant/antioxidant status, increased inflammatory cytokines and fibrosis. Sildenafil (20mg/kg/day) was the most protective one, it caused upregulation of SIRT1, reduction of hepatic malondialdehyde (MDA) content, increase in expression of nuclear factor erythroid 2-related factor 2 (Nrf2), hemeoxygenease (HO)-1, reduced glutathione (GSH) content and superoxide dismutase (SOD) activity. Hepatic content of tumor necrosis factor-α (TNF-α) and nuclear factor κB (NFκB) expression & content displayed significant reductions with sildenafil treatment, Furthermore, sildenafil caused marked reductions of transforming growth factor (TGF)-ß content, expression of plasminogen activator inhibitor-1 (PAI-1), matrix metalloproteinase-9 (MMP-9), tissue inhibitor of metalloproteinase-1 (TIMP-1), α-smooth muscle actin (α-SMA), fibronectin, collagen I (α1) and hydroxyproline content. However, sildenafil protective effects were significantly reduced by co-administration of EX527 (SIRT1 inhibitor). Our work showed, for the first time that, sildenafil has promising protective effects against BDL induced liver dysfunction and hepatic fibrosis. These effects may be, in part, mediated by up regulation of SIRT1.

GSK-3ß heterozygous knockout is cardioprotective in a knockin mouse model of familial dilated cardiomyopathy.

Glycogen synthase kinase-3ß (GSK-3ß) plays a central role in both cardiac physiology and pathology. Herein we want to clarify the role of GSK-3ß in familial dilated cardiomyopathy. We generated a mouse model carrying a heterozygous knockout mutation of GSK-3ß (GSK-3ß(+/-) KO), together with a ΔK210 knockin mutation in cardiac troponin T (ΔK210 cTnT KI), which was proved to be one of the genetic causes of familial dilated cardiomyopathy (DCM). GSK-3ß(+/-) KO prevented the slow and rapid deterioration in left ventricular systolic function accompanying heart failure (HF) in DCM mice with heterozygous and homozygous ΔK210 cTnT KI mutations, respectively. GSK-3ß(+/-) KO also prevented cardiac enlargement, myocardial fibrosis, and cardiomyocyte apoptosis and markedly reduced the expression of cardiac ß-myosin heavy chain isoform, indicative of HF, in DCM mice with homozygous ΔK210 cTnT KI mutation. GSK-3ß(+/-) KO also extended the life span of these DCM mice. This study suggests that the inhibition of GSK-3ß is cardioprotective in familial DCM associated with ΔK210 cTnT mutation.

Ezrin, radixin, and moesin phosphorylation in NIH3T3 cells revealed angiotensin II type 1 receptor cell-type-dependent biased signaling.

ß-Arrestin-biased agonists are a new class of drugs with promising therapeutic effects. The molecular mechanisms of ß-arrestin-biased agonists are still not completely identified. Here, we investigated the effect of angiotensin II (AngII) and [Sar1,Ile4,Ile8] AngII (SII), a ß-arrestin-biased agonist, on ezrin-radixin-moesin (ERM) phosphorylation in NIH3T3 cells (a fibroblast cell line) stably expressing AngII type 1A receptor. ERM proteins are cross-linkers between the plasma membrane and the actin cytoskeleton and control a number of signaling pathways. We also investigated the role of Gαq protein and ß-arrestins in mediating ERM phosphorylation. We found that AngII stimulates ERM phosphorylation by acting as a ß-arrestin-biased agonist and AngII-stimulated ERM phosphorylation is mediated by ß-arrestin2 not ß-arrestin1. We also found that SII inhibits ERM phosphorylation by acting as a Gαq protein-biased agonist. We concluded that ERM phosphorylation is a unique ß-arrestin-biased agonism signal. Both AngII and SII can activate either Gαq protein or ß-arrestin-mediated signaling as functional biased agonists according to the type of the cell on which they act.

ß-arrestin-mediated signaling improves the efficacy of therapeutics.

ß-Arrestins (ß-arrestin-1 and ß-arrestin-2) were first identified as proteins that have the ability to desensitize G protein-coupled receptors (GPCRs). However, it has recently been found that ß-arrestins can activate signaling pathways independent of G protein activation. The diversity of these signaling pathways has also been recognized. This leads to an appreciation of ß-arrestin-biased agonists, which is a new class of drugs that selectively activate ß-arrestin-mediated signaling without G protein activation. In this review, we will discuss the recent advance of ß-arrestin-mediated signaling pathways, including a brief account of different biased agonists, their pharmacological applications, and novel ß-arrestin research.