Toll-Like Receptor 4 (TLR4) and AMPK Relevance in Cardiovascular Disease.

Toll-like receptors (TLRs) are essential receptors of the innate immune system, playing a significant role in cardiovascular diseases. TLR4, with the highest expression among TLRs in the heart, has been investigated extensively for its critical role in different myocardial inflammatory conditions. Studies suggest that inhibition of TLR4 signaling pathways reduces inflammatory responses and even prevents additional injuries to the already damaged myocardium. Recent research results have led to a hypothesis that there may be a relation between TLR4 expression and 5' adenosine monophosphate-activated protein kinase (AMPK) signaling in various inflammatory conditions, including cardiovascular diseases. AMPK, as a cellular energy sensor, has been reported to show anti-inflammatory effects in various models of inflammatory diseases. AMPK, in addition to its physiological acts in the heart, plays an essential role in myocardial ischemia and hypoxia by activating various energy production pathways. Herein we will discuss the role of TLR4 and AMPK in cardiovascular diseases and a possible relation between TLRs and AMPK as a novel therapeutic target. In our opinion, AMPK-related TLR modulators will find application in treating different immune-mediated inflammatory disorders, especially inflammatory cardiac diseases, and present an option that will be widely used in clinical practice in the future.

Time-dependent influence of infliximab on hemodynamic responses and cardiac injuries of isoproterenol-induced myocardial infarction in rats.

Immune-induced inflammation plays an important role both in aggravating and healing of post myocardial infarction (MI) injuries. Potent anti-inflammatory and local immunomodulatory activity of infliximab has been suggested to have modulating effects on immune responses after MI. The aim of the present study was to evaluate the efficacy of infliximab on hemodynamic responses and myocardial injuries following isoproterenol-induced myocardial infarction. Male Wistar rats, weighting 260 ± 20 g were assigned into ten groups (n = 6) of saline (normal saline), infliximab (7 mg/kg), isoproterenol (100 mg/kg for two consecutive days), and isoproterenol plus infliximab (30 min after the second injection of isoproterenol). The heart tissues and serums were analyzed 24, 48, 72, and 96 h post-MI and hemodynamic parameters, histopathological changes, malondialdehyde (MDA), Total antioxidant capacity (TAC), lactate dehydrogenase (LDH), and lactate levels were assessed in the respective groups. Infliximab partially improved hemodynamic depression in the first days after MI, but the heart became more suppressed later. A similar result also obtained at the MDA tissue levels but not serum levels. Anti-inflammatory effects of Infliximab may improve cardiac function and prevent heart tissue injury early after MI; however, it can worsen the condition later by inhibiting compensatory reactions such as cardiac remodeling and tissue repair.

Metformin-attenuated sepsis-induced oxidative damages: a novel role for metformin.

OBJECTIVES: Sepsis can result in severe organ injury by provoking inflammatory cascades and oxidative stress. Several studies are currently underway to find a drug with anti-inflammatory effects to prevent mortality and morbidity during sepsis. The present study was undertaken to assess the effects of metformin on oxidative stress and antioxidant status in sepsis induced by the Cecal Ligation and Puncture (CLP) method. MATERIALS AND METHODS: Male Wistar rats were divided into 4 groups (n=10): sham, CLP, and 50 and 100 mg/kg metformin-treated CLP groups. After 12 hr, blood samples were collected and lung tissue was removed for histopathological study to detect tissue damage and degree of inflammation based on neutrophil infiltration and assay of the oxidative stress biomarkers superoxide dismutase (SOD), total antioxidant capacity (TAC), malondialdehyde (MDA), myeloperoxidase (MPO), glutathione peroxidase (GPx), and plasminogen activator inhibitor-1 (PAI-1). RESULTS: The MPO activity and MDA level were decreased in the metformin-treated groups (P<0.05). Moreover, the groups receiving metformin showed lower inflammation scores than the CLP group (P<0.05). No significant differences in SOD, GPx, or PAI in the different groups were observed. The TAC level was reduced in the CLP group compared to the sham group (P<0.05), and interestingly, this value was reduced even further in the metformin-treated groups (P<0.05 compared with the CLP group). CONCLUSION: It was concluded that metformin protects lung tissue against sepsis-induced oxidative damage, and this protective effect may be more related to its anti-inflammatory and reduced neutrophil accumulation and less to its anti-oxidative properties.

Screening of Anti-Malarial Activity of Different Extracts Obtained from Three Species of Scrophularia Growing in Iran.

Scrophularia genus belonging to the family of Scrophulariaceae, is a medicinal plant widely distributed in Iran. In the present study, the anti-malarial activity of different extracts of three Iranian endemic species of Scrophularia including S. frigida, S. subaphylla and S. atropatana, was screened by an in-vitro preliminary assay. The plant materials were extracted successively with n-hexane, dichloromethane (DCM), and methanol (MeOH) at room temperature by soxhlet extractor. In order to assess anti-malarial activity of obtained extracts, cell free ß-hematin formation assay was applied. Amongst the extracts, DCM extract of S. frigida exhibited remarkable anti-malarial activity with IC50 value of 0.67 ± 0.11 mg/mL. In contrast, MeOH and n-hexane extracts of all plants illustrated insignificant or moderate activity in this assay. Furthermore, preliminary phytochemical analysis along with TLC and GC-MS analysis of potent extract (DCM extract of S. frigida) were performed for more clarification. These methods revealed that the notable anti-malarial activity might be due to the presence of active constituents like methoxylated flavonoids, methylated coumarins, and diterpenoids. From the nine extracts of different species of Scrophularia, DCM extract of S. frigida showed potent inhibitory activity on ß-hematin formation assay. Hence, it seems that it is noteworthy to concentrate on purifying the active chemical constituents of DCM extract and determining the pure anti-malarial components.

Cardioprotective Effects of Methanolic Extract of Scrophularia frigida on Ischemia-Reperfusion-Induced Injuries in Isolated Rat Heart.

Myocardial infarction is a common presentation of coronary artery disease and the leading cause of death worldwide. The present study investigated potential resistance to ischemia-reperfusion (I/R) injuries following administration of methanolic (MeOH) extract of Scrophularia frigida (S. frigida) in isolated rat heart. Male Wistar rat hearts (n= 8-10) were isolated and allowed to equilibrate for 20 min, and then subjected to 30 min regional ischemia followed by 120 min reperfusion. In the control group, Krebs-Henseleit (K/H) solution was perfused. However, in the treatment groups K/H solution containing 1, 5, and 10 µg/cc of extract was infused. In addition, total phenol, total flavonoid content and antioxidant property were evaluated and extract was subjected to phytochemical analysis. Administration of extract improved the flow rate, developed pressure as well as max and min left ventricular dp/dt. Number and duration of VT were significantly reduced by all extract concentrations in ischemic phase. In reperfusion phase, significant decreases in single and total arrhythmias were seen. Furthermore, concentrations of 5 and 10 µg/cc of extract remarkably decreased the infarct size. Generally, the methanolic extract of S. frigida exhibited a protective effect against I/R-induced injures, which might be due to the antioxidant activiies of iridoids and phenolics.

AMPK activation by metformin inhibits local innate immune responses in the isolated rat heart by suppression of TLR 4-related pathway.

Toll like receptors (TLRs) are key players in the innate immune responses. The energy sensing enzyme, AMPK, has been implicated in the modulation of immunity. The present study investigated whether AMPK activation by metformin could contribute to the regulation of immune responses in the isolated heart via suppression of TLR4 activity, independent of circulatory immunity. Isolated Wistar rat hearts were perfused with Krebs-Henseleit buffer in the absence or presence of lipopolysaccharide (LPS; 0.2µM), LPS+metformin (10mM), and LPS+metformin+compound C (10µM). Following measurement of hemodynamic parameters, TLR4-activation related changes and TLR4 mRNA level in the heart was examined by western blotting and real-time PCR. The activation of AMPK was evaluated by measuring the ratio of p-AMPKα and p-ACC to their non-phosphorylated forms. The effluent and cardiac levels of TNF-α and IL6 were assayed by ELISA. LPS profoundly increased the levels of TLR4 mRNA, MyD88 (TLR4 adaptor protein), and NF-κB and also the release of TNF-α and IL6 from the heart. The enhancement in the TLR4 activity was associated with a significant depression of myocardial function. Metformin clearly augmented the phosphorylation of both AMPKα and ACC and in addition to improvement of cardiac performance, markedly suppressed the TLR4 activity. Antagonizing AMPK by compound C which is a selective inhibitor of AMPK pathway, considerably reversed the protective effects of metformin against the TLR4-related activity. The results of the study demonstrated the importance of TLR4-involved local immune responses in the LPS-induced myocardial dysfunction and indicated a clear link between AMPK and TLR4.

A-769662, a direct AMPK activator, attenuates lipopolysaccharide-induced acute heart and lung inflammation in rats.

Activation of AMP­activated protein kinase (AMPK) has been indicated to produce an anti­inflammatory effect through the suppression of toll­like receptor (TLR) activity. In the present study, the investigation was designed to identify the effect of A­769662, a direct activator of AMPK on lipopolysaccharide (LPS)­induced acute lung and heart inflammation in rats. To induce inflammation, an intraperitoneal injection of LPS (0.5 mg/kg) was administered to Wistar rats. The inflammatory parameters and AMPK phosphorylation were then measured 9 h later. For the treatment group, A­769662 (10 mg/kg) was administrated intraperitoneally immediately prior to LPS injection. The results demonstrated that A­769662 attenuated the LPS­induced acute inflammation in the heart and lung tissue, as indicated by the significant reduction in myeloperoxidase activity (P<0.001) and inhibition of tissue damage. This was associated with a significant reduction in tumor necrosis factor­α serum levels (P<0.01) and peripheral neutrophils (P<0.001). Furthermore, A­769662 enhanced AMPK phosphorylation and downregulated the expression of MyD88, a TLR adaptor protein, in the heart tissue. Despite the anti­inflammatory effect of A­769662 on LPS­induced inflammation in the lung tissue, the drug produced no effect on the MyD88 expression levels or AMPK phosphorylation in the tissue. The results of the present study suggested that the administration of A­769662 results in an anti­inflammatory effect in the LPS­induced model of inflammation in rats. The anti­inflammatory activity was demonstrated in the heart and lung tissues and the effect on the cardiac tissue was indicated to be a result of AMPK activation, involving the suppression of TLRs.

Metformin Alleviates Lipopolysaccharide-induced Acute Lung Injury through Suppressing Toll-like Receptor 4 Signaling.

Signaling AMP-activated protein kinase (AMPK), an energy sensing enzyme, has been implicated in controlling inflammation. In this study we investigated whether activation of AMPK by metformin could protect the lung from lipopolysaccharide (LPS)-induced acute injury by inhibitingng TLR4 pathway. Male Wistar rats were randomly divided into 3 groups (n=6): control group received normal saline (0.5 mL), LPS group received LPS (0.5 mg/kg), and metformin-treated group received LPS and metformin (100 mg/kg). Nine hours later nuclear factor-κB (NF-κB), phosphorylated, and non-phosphorylated AMPK using western blot, and the rate of TLR4 mRNA expression using real-time PCR were assessed in the lung tissue. To evaluate neutrophil infiltration, the myeloperoxidase (MPO) activity was measured. The severity of the lung damage was assessed by histological examinations. It was found that the ratio of p-AMPKα to AMPKα was significantly upregulated by 22% (p<0.05) in the lungs obtained from the metformin group. In LPS-treated rats, we observed a high expression of TLR4 in the tissue along with increased levels of MyD88, NF-κB, and TNFα. Metformin considerably reduced all these parameters. Histological examinations revealed that metformin remarkably attenuated congestion and inflammatory cellular infiltration into the alveolar walls and also decreased MPO activity by 37% (p<0.05). We conclude that metformin could protect the lung tissue against LPS-evoked TLR4 activation and the protective effect can be related to the activation of AMPK.

Cardioprotective effect of metformin in lipopolysaccharide-induced sepsis via suppression of toll-like receptor 4 (TLR4) in heart.

Sepsis-induced myocardial dysfunction is a serious organ complication. In the present study, we investigated the effect of metformin on myocardial dysfunction and TLR4 activity in LPS-induced sepsis. Male Wistar rats were randomly divided into 3 groups (n=6): control received normal saline (0.5ml), LPS group received lipopolysaccharide (0.5mg/kg; i.p), and metformin treated group received LPS (0.5mg/kg)+metformin (100mg/kg; i.p). 9h later the hemodynamic parameters were recorded, blood samples were collected, and the hearts were removed and weighted. The concentration of TNF-α, content of MYD88, the phosphorylation of AMPK, and the rate of TLR4 expression in the heart were assessed. In the animals treated with metformin, the preservation of left ventricular function was associated with the reduction of myeloperoxidase activity (31%, P<0.01) in the heart and decrease of TNF-α level both in the serum and heart tissue (20%, P<0.01 and 42%, P<0.05, respectively). It was found that the level of phosphorylated AMPK in heart was significantly upregulated by 43% (P<0.001) in the metformin group while the content of TLRs adapter protein of MyD88 was reduced by 45% (P<0.05). This was associated with a remarkable decrease in the expression of myocardial TLR4. Furthermore, in a mice model of sepsis, coadministration of compound C (20mg/kg) as an AMPK inhibitor reversed the suppressive effects of metformin on TLR4 expression and MYD88 protein level. These results suggest that metformin exhibits cardioprotective effects in sepsis by suppression of TLR4 activity, at least in part through pathways involving AMPK activation.

Lipopolysaccharide Induced Activation of Toll Like Receptor 4 in Isolated Rat Heart Suggests a Local Immune Response in Myocardium.

BACKGROUND: Myocardial dysfunction is one of the major complications in patients with sepsis where there is a relationship between the blood level of cytokines and the onset of myocardial depression. In many cases of sepsis, the presence of Lipopolysaccharide (LPS) has been established. LPS Binding Protein (LBP) bound endotoxin is recognized by CD14/toll-like receptor-4 (TLR4) complexes in innate immune cells which stimulates TNF-α release. OBJECTIVES: To investigate whether isolated rat heart is capable of producing TNF-α locally through TLR4 activation by LPS. METHODS: Using langendorff method, LPS in 120 mL of the modified Krebs-Henseleit buffer solution (KHBS) at final concentration of 1 µg/mL was perfused at recycling mode. The effect of LPS on cardiac function was evaluated. To assess the TLR4 activity and TNF-α release, western blotting, real time-PCR, and ELISA were used. RESULTS: Compared with control, coronary perfusion pressure (CPP) as well as left ventricular developed pressure (LVDP), maximum and minimum rates of the left ventricular developed pressure (dP/dtmax; dP/dtmin; p<0.001) were depressed to a maximum level after 180 minutes recycling with LPS. This myocardial depression was associated with a significant increase in TLR4 expression (p<0.01), MyD88 activity (p<0.01) and TNF-α (p<0.05) concentration in the heart tissue. CONCLUSION: The results of this study show that heart is capable of producing TNF-α through TLR4 and MyD88 activation independent of classic immune system and suggest a local immune response.

Impact of caffeine on weight changes due to ketotifen administration.

PURPOSE: Prescription of ketotifen as an effective antihistamine in asthma and allergic conditions is associated with side effect of weight gain. Caffeine is an agent which increases thermogenesis and improves energy expenditure and also effective in asthma. The aim of current study was to evaluate caffeine impact in reducing weight gain side effect of ketotifen. METHODS: Male mice at the weight limit of 20-30 gr in 8 groups were randomly chosen and injected following drug dosages for 45 days intraperitoneally: control group (normal saline 10 ml/kg), three groups of ketotifen (4, 8, 16 mg/kg), three groups of caffeine (4, 8, 16 mg/kg) and one group of ketotifen (4 mg/kg) in combination with caffeine (4 mg/kg). Weight changes have been recorded and assessed every 3 days for 45 days. RESULTS: The results showed that in all dosages of the two drugs, significant weight loss occurred in comparison with the control group. CONCLUSION: The effect of caffeine on weight loss according to our results, matches with human studies, while ketotifen contradictory to our assumption, resulted in weight loss which probably was related to the difference in metabolic pathways in mice and humans, or maybe the used doses of ketotifen in this study were insufficient to reduce TNF-α production or influence in serotonin release and be effective on appetite or weight gain.

Attenuation of morphine-induced dependence and tolerance by ceftriaxone and amitriptyline in mice.

INTRODUCTION: Tolerance to and dependence on the analgesic effect of opioids is a pharmacological phenomenon that occurs after their prolonged administration. OBJECTIVE: The aim of this study was to evaluate the protective effects of ceftriaxone and amitriptyline on the development of morphine-induced tolerance and dependence. METHODS: In this study, 18 groups (9 groups each for tolerance and dependency tests) of mice (n = 8) received saline [10 mL/kg, intraperitoneally (i.p.)], morphine (50 mg/kg, i.p.), ceftriaxone (50 mg/kg, i.p., 100 mg/kg, i.p., and 200 mg/kg, i.p.), amitriptyline (5 mg/kg, i.p., 10 mg/kg, i.p., and 15 mg/kg, i.p.), or a combination of ceftriaxone (50 mg/kg, i.p.) and amitriptyline (5 mg/kg, i.p.) once per day for 4 days for investigation and comparison of the effects of ceftriaxone and amitriptyline on the prevention of dependency and tolerance to morphine. Tolerance was assessed with administration of morphine (9 mg/kg, i.p.) and using the hot plate test on the 5(th) day. In dependency tests, withdrawal symptoms were assessed on the 4(th) day for each animal 30 minutes after the administration of naloxone (4 mg/kg, i.p.; 2 hours after the last dose of morphine). RESULTS: It was found that treatment with ceftriaxone or amitriptyline attenuated the development of tolerance to the antinociceptive effect of morphine and also reduced naloxone-precipitated withdrawal jumping and standing on feet. Furthermore, coadministration of ceftriaxone and amitriptyline at low doses (50 mg/kg, i.p. and 5 mg/kg, i.p., respectively) prior to morphine injection also decreased both morphine-induced tolerance and dependence. CONCLUSION: Results indicate that the treatment with ceftriaxone and amitriptyline, alone or in combination, could attenuate the development of morphine-induced tolerance and dependence.

Zero flow global ischemia-induced injuries in rat heart are attenuated by natural honey.

PURPOSE: In the present study, effects of preischemic administration of natural honey on cardiac arrhythmias and myocardial infarction size during zero flow global ischemia were investigated in isolated rat heart. METHODS: The isolated hearts were subjected to 30 min zero flow global ischemia followed by 120 min reperfusion then perfused by a modified drug free Krebs-Henseleit solution throughout the experiment (control) or the solution containing 0.25, 0.5, 1 and 2% of natural honey for 15 min before induction of global ischemia (treated groups), respectively. Cardiac arrhythmias were determined based on the Lambeth conventions and the infarct size was measured by computerized planimetry. RESULTS: Myocardial infarction size was 55.8±7.8% in the control group, while preischemic perfusion of honey (0.25, 0.5, 1 and 2%) reduced it to 39.3±11, 30.6±5.5 (P<0.01), 17.9±5.6 (P<0.001) and 8.7±1.1% (P<0.001), respectively. A direct linear correlation between honey concentrations and infarction size reduction was observed (R(2)=0.9948). In addition, total number of ventricular ectopic beats were significantly decreased by all used concentrations of honey (P<0.05) during reperfusion time. Honey (0.25, 0.5 and 1 %) also lowered incidence of irreversible ventricular fibrillation (P<0.05). Moreover, number and duration of ventricular tachycardia were reduced in all honey treated groups. CONCLUSION: Preischemic administration of natural honey before zero flow global ischemia can protect isolated rat heart against ischemia/reperfusion injuries as reduction of infarction size and arrhythmias. Maybe, antioxidant and free radical scavenging activities of honey, reduction of necrotized tissue and providing energy sources may involve in these cardioprotective effects of honey.

Resistance to reperfusion injury following short term postischemic administration of natural honey in globally ischemic isolated rat heart.

PURPOSE: RESULTS of our previous study revealed that preischemic perfusion of honey before zero flow global ischemia had cardioprotective effects in rat. The present study investigated potential resistance to reperfusion injury following short term postischemic administration of natural honey in globally ischemic isolated rat heart. METHODS: Male Wistar rats were divided into five groups (n=10-13). The rat hearts were isolated, mounted on a Langendorff apparatus, allowed to equilibrate for 30 min then subjected to 30 min global ischemia. In the control group, the hearts were reperfused with drug free normal Krebs-Henseleit (K/H) solution before ischemia and during 120 min reperfusion. In the treatment groups, reperfusion was initiated with K/H solution containing different concentration of honey (0.25, 0.5, 1 and 2%) for 15 min and was resumed until the end of 120 min with normal K/H solution. RESULTS: In the control group, VEBs number was 784±199, while in honey concentration of 0.25, 0.5, 1 and 2%, it decreased to 83±23 (P<0.001), 138±48 (P<0.01), 142±37 (P<0.001) and 157±40 (P<0.01), respectively. Number and duration of VT and time spent in reversible VF were also reduced by honey. In the control group, the infarct size was 54.1±7.8%, however; honey (0.25, 0.5, 1 and 2%) markedly lowered the value to 12.4±2.4, 12.7±3.3, 11.3±2.6 and 7.9±1.7 (P<0.001), respectively. CONCLUSION: Postischemic administration of natural honey in global ischemia showed protective effects against ischemia/reperfusion (I/R) injuries in isolated rat heart. Antioxidant and radical scavenging activity, lipoperoxidation inhibition, reduction of necrotized tissue, presence of rich energy sources, various type of vitamins, minerals and enzymes and formation of NO-contain metabolites may probably involve in those cardioprotective effects.