New aspects of cyclooxygenase-2 inhibition in myocardial infarction and ischaemia

We have investigated the role of cyclooxygenase-2 (COX-2) in myocardial infarction (MI) and ischaemia in rabbits subjected to isoprenaline (ISP) a potent beta-adrenergic agonist. The acute phases of MI and repair mimicked those which occurred in humans. MI after induction with ISP was monitored by following increases seen in the levels of serum enzymes, Troponin I and Creatinine phosphokinase (CPK) in rabbits before and after ISP induced MI. Electrocardiographic (ECG) changes showed typical ST elevation and q-wave development. Histochemical studies of the rabbit heart on 2nd day after ISP injection showed changes of coagulation necrosis. Day 4 total coagulation with the loss of nuclear and striation associated with heavy interstitial infiltrate of neutrophils was found. Day 8 after infarction showed collagen deposition with capillary channels in between the remaining islands of myocytes in the infarcted area on the 16th day scarring was complete. Coronary perfusion rates (CPR) of the infarcted and nimesulide (a COX-2 inhibitor) treated rabbits displayed significant improvement on each corresponding day after infarction as compared to the infarcted and saline treated rabbits (P<0.01). These results suggest that nimesulide, a COX-2 inhibitor exhibit cardioprotective effects in MI.

Studies on the protective effects of caffeic acid and quercetin on chemical-induced hepatotoxicity in rodents

Caffeic acid and quercetin, the well-known phenolic compounds widely present in the plant kingdom, were investigated for their possible protective effects against paracetamol and CCl4-induced hepatic damage. Paracetamol at the oral dose of 1 g/kg produced 100% mortality in mice while pretreatment of separate groups of animals with caffeic acid (6 mg/kg) and quercetin (10 mg/kg) reduced the death rate to 20% and 30%, respectively. Oral administration of sub-lethal dose of paracetamol (640 mg/kg) produced liver damage in rats as manifested by the significant (P<0.01) rise in serum levels of aminotransferases (aspartate transaminase (AST) and alanine transaminase (ALT)) compared to respective control values. The serum enzyme values were significantly (P<0.01) lowered on pretreatment of rats with either caffeic acid (6 mg/kg) or quercetin (10 mg/kg). Similarly, the hepatotoxic dose of CCl4 (1.5 ml/kg; orally) also raised significantly (P<0.05) the serum AST and ALT levels as compared to control values. The same dose of the caffeic acid and quercetin was able to prevent CCl4-induced rise in serum enzymes. Caffeic acid and quercetin also prevented the CCl4-induced prolongation in pentobarbital sleeping time confirming their hepatoprotectivity. These results indicate that caffeic acid and quercetin exhibited hepatoprotective activity possibly through multiple mechanisms.

Plasma from rheumatoid patients taking low dose methotrexate enhances platelet aggregation

Methotrexate (MTX) in low doses is commonly used to treat rheumatoid arthritis (RA). At least 36 deaths have been attributed to bone marrow cytotoxicity associated with low dose MTX. The goal was to determine if plasma from arthritis patients taking low dose MTX induces platelet aggregation in platelet rich plasma from healthy volunteers. Plasma from patients on MTX alone caused a 3-fold increase in aggregation vs plasma from controls (P<0.05). Plasma from patients not taking MTX or taking MTX with diclofenac caused aggregation to a lesser extent. Diclofenac, along with several others NSAIDs and cyclooxygenase inhibitors, depressed aggregation produced by arachidonic acid in platelet rich plasma from healthy volunteers. A precise mechanism for amplification of aggregation by MTX plasma and its relationship to MTX toxicity remains unknown. However, a serum factor may be produced by MTX that modulates the activity of cyclooxygenase, thereby influencing aggregation.

Molecular mechanisms involved in human platelet aggregation by synergistic interaction of platelet-activating factor and 5-hydroxytryptamine

Our recent studies have shown that co-activation of Gq and Gi proteins by 5-hydroxytryptamine (5-HT) and adrenaline show synergism in human platelet aggregation. This study was conducted to examine the mechanism(s) of synergistic interaction of 5-HT and platelet activating factor (PAF) in human platelets. We show that PAF, but not 5-HT, increased platelet aggregation in a concentration-dependent manner. However, low concentrations of 5-HT (2 microM) potentiated platelet aggregation induced by subthreshold concentration of PAF (40 nM) indicating a synergistic interaction between the two agonists and this synergism was blocked by receptor antagonists to either 5-HT or PAF. 5-HT also potentiated the effect of PAF on thromboxane A2 (TXA2) formation and phosphorylation of extracellularly regulated mitogen-activated protein kinases (ERK1/2). The synergism of 5-HT and PAF in platelet aggregation was inhibited by calcium (Ca2+) channel blockers, verapamil and diltiazem, phospholipase C (PLC) inhibitor, U73122, cyclooxygenase (COX) inhibitor, indomethacin, and MEK inhibitor, PD98059. These data suggest that synergistic effect of 5-HT and PAF on human platelet aggregation involves activation of PLC/Ca2+, COX and MAP kinase pathways.

Second messengers in platelet aggregation evoked by serotonin and A23187, a calcium ionophore

We investigated the combined effect of 5-hydroxytryptamine (5-HT, serotonin) and calcium ionophore (A23187) on human platelet aggregation. Aggregation, monitored at 37 degrees C using a Dual-channel Lumi-aggregometer, was recorded for 5 min after challenge by a change in light transmission as a function of time. 5-HT (2-200 microM) alone did not cause platelet aggregation, but markedly potentiated A23187 (low dose) induced aggregation. Inhibitory concentration (IC50) values for a number of compounds were calculated as means +/- SEM from dose-response determinations. Synergism between 5-HT (2-5 microM) and A23187 (0.5-2 microM) was inhibited by 5-HT receptor blockers, methysergide (IC50 = 18 microM) and cyproheptadine (IC50 = 20 microM), and calcium channel blockers (verapamil and diltiazem, IC50 = 20 microM and 40 microM respectively). Interpretation of the effects of these blockers is complicated by their lack of specificity. Similarly, U73122, an inhibitor of phospholipase C (PLC), blocked the synergistic effect at an IC50 value of 9.2 microM. Wortmannin, a phosphatidylinositide 3-kinase (PI 3-K) inhibitor, also blocked the response (IC50 = 2.6 microM). However, neither genistein, a tyrosine-specific protein kinase inhibitor, nor chelerythrine, a protein kinase C inhibitor, affected aggregation at concentrations up to 10 microM. We conclude that the synergistic interaction between 5-HT and ionophore may be mediated by activation of PLC/Ca2+ and PI 3-kinase signalling pathways, but definitive proof will require other enzyme inhibitors with greater specificity.

Wortmannin inhibits platelet aggregation produced by interaction of gamma-aminobutyric acid and the calcium tonophore, A23187

Platelet aggregation by gamma-aminobutyric acid (GABA) agonists combined with a calcium ionophore was studied. GABA, baclofen and mucimol markedly amplified aggregatory responses to a subthreshold concentration of the ionophore, A23187. This effect was inhibited by wortmannin, a blocker of phosphoinositide 3-kinase. However, several antagonists of GABA receptors had no effect on the response, and benzodiazepines inhibited aggregation. These results suggest that the GABA effect is not mediated by traditional neuronal GABA receptors. We propose that wortmannin inhibits aggregation at a nexus downstream from membrane mechanisms triggered by the GABA-A23187 interaction.

Acute diquat poisoning with intracerebral bleeding

A case of severe diquat poisoning complicated by the development of aggressive behaviour, oliguric renal failure, and intracerebral bleeding is described. The patient was successfully managed and made a complete recovery. In this paper special attention has been given to the major clinical differences between diquat and paraquat intoxication.

Hypotensive action of coumarin glycosides from Daucus carota

Daucus carota (carrot) has been used in traditional medicine to treat hypertension. Activity-directed fractionation of aerial parts of D. carota resulted in the isolation of two cumarin glycosides coded as DC-2 and DC-3. Intravenous administration of these compounds caused a dose-dependent (1-10 mg/kg) fall in arterial blood pressure in normotensive anaesthetised rats. In the in vitro studies, both compounds caused a dose-dependent (10-200 microg/ml) inhibitory effect on spontaneously beating guinea pig atria as well as on the K+ -induced contractions of rabbit aorta at similar concentrations. These results indicate that DC-2 and DC-3 may be acting through blockade of calcium channels and this effect may be responsible for the blood pressure lowering effect of the compounds observed in the in vivo studies.

Cefuroxime induced lymphomatoid hypersensitivity reaction

An 84 year old woman developed erythematous blotchy erythema and purpuric rashes over the lower limbs three days after being started on intravenous cefuroxime for acute diverticulitis. A skin biopsy specimen showed a mixed infiltrate of lymphoid cells and eosinophils; many of the lymphocytes were large, pleomorphic, and showed a raised mitotic rate. Immunohistochemistry showed the infiltrate to be T cell rich, with all the large cells being CD30 positive. Typical mycosis fungoides cells, marked epidermotropism, and Pautrier's abscesses were not seen. The rash disappeared 10 days after cessation of cefuroxime and the patient remained asymptomatic 15 months later. This apparent cutaneous T cell lymphoma-like reaction is best described as lymphomatoid vascular reaction. The drug induced immune response with an atypical cutaneous lymphoid infiltrate mimics a cutaneous pseudolymphoma.

Paan without tobacco: an independent risk factor for oral cancer

Oral cancer is the second most common cancer in women and the third most common in men in Pakistan. Tobacco is smoked and chewed extensively in Pakistan. Paan is a quid of piper betel leaf that contains areca nut, lime, condiment, sweeteners, and sometimes tobacco, which is also used extensively. We did this study to clarify the independent association of paan and oral cancer. Between July 1996 and March 1998, we recruited biopsy-proven, primary cases of oral squamous-cell carcinoma, from 3 tertiary teaching centers in Karachi, Pakistan, and controls pair-matched for age, gender, hospital and time of occurrence, excluding persons with a past or present history of any malignancy. There were 79 cases and 149 controls. Approximately 68% of the cases were men, 49 years old on average, the youngest being 22 years old and the eldest 80. People with oral submucous fibrosis were 19.1 times more likely to develop oral cancer than those without it, after adjusting for other risk factors. People using paan without tobacco were 9.9 times, those using paan with tobacco 8.4 times, more likely to develop oral cancer as compared with non-users, after adjustment for other covariates. This study identifies an independent effect of paan without tobacco in the causation of oral cancer. Its findings may be of significance in South Asian communities where paan is used, and among health-care providers who treat persons from South Asia.

Social anxiety disorder: a common, underrecognized mental disorder

Social phobia is a highly prevalent yet often overlooked psychiatric disorder that can cause severe disability but fortunately has shown responsiveness to specific pharmacotherapy and psychotherapy. Recognition of its essential clinical features and the use of brief, targeted screening questions can improve detection within family practice settings. Cognitive behavioral therapy, with or without specific antidepressant therapy, is the evidence-based treatment of choice for most patients. Adjunctive use of benzodiazepines can facilitate the treatment response of patients who need initial symptom relief. The use of beta blockers as needed has been found to be helpful in the treatment of circumscribed social and performance phobias. Treatment planning should consider the patient's preference, the severity of presenting symptoms, the degree of functional impairment, psychiatric and substance-related comorbidity, and long-term treatment goals.

Additive effect of indomethacin and methotrexate on suppression of growth in rats

The purpose of this study was to investigate the medium-term effects of methotrexate (MTX) and indomethacin on the growth of young rats. Four equal groups of Sprague-Dawley male rats (four animals in each group; mean+/-S.D. body weight, 183+/-13 g, in their rapid growth phase) were subjected to the following drug treatment: one group was given MTX (0.2 mg kg(-1) body weight) subcutaneously on every fourth day, another received indomethacin (2.5 mg kg(-1) body weight) subcutaneously daily and the third group was given both of these drugs (MTX on every fourth day and indomethacin daily). The fourth group was injected subcutaneously with physiological saline every day to serve as a control group. Total body weight, food and water consumption by animals in each group were monitored every second day for a period of 10 weeks. After this period, liver, spleen and kidneys were excised, weighed and analysed for MTX and dihydrofolate reductase activity. Compared with the groups, which received MTX alone, indomethacin alone, or physiological saline, mean increase (17+/-11 g) in body weight of rats was minimal in the group receiving both MTX and indomethacin. The difference was statistically significant (p=0.001) when the values of mean increase in body weight of rats in different treatment groups after a 10-week treatment were compared. The mean weights of liver and spleen in this group receiving both MTX and indomethacin were also found to be significantly less than the weights of these organs in the control group (p<0.01). There also appears to be a decline in food consumption in this group (p<0.05). This negative effect on growth of animals in this group appears to be not only due to decreased food consumption but also due to increased inhibition of de novo pathway of DNA synthesis. This is supported by increased accumulation of MTX and decreased dihydrofolate reductase activity in this group receiving both MTX and indomethacin, as compared with the group receiving MTX alone. The data indicate an additive effect of MTX and indomethacin on the suppression of growth in young rats, alluding to the notion that patients suffering from juvenile rheumatoid arthritis or acute lymphoblastic leukaemia receiving these two drugs concomitantly over a long period of time might be at a risk of experiencing short-term suppression of growth.

Inhibitory effect of curcumin, a food spice from turmeric, on platelet-activating factor- and arachidonic acid-mediated platelet aggregation through inhibition of thromboxane formation and Ca2+ signaling

Curcumin, a dietary spice from turmeric, is known to be anti-inflammatory, anticarcinogenic, and antithrombotic. Here, we studied the mechanism of the antiplatelet action of curcumin. We show that curcumin inhibited platelet aggregation mediated by the platelet agonists epinephrine (200 microM), ADP (4 microM), platelet-activating factor (PAF; 800 nM), collagen (20 microg/mL), and arachidonic acid (AA: 0.75 mM). Curcumin preferentially inhibited PAF- and AA-induced aggregation (IC50; 25-20 microM), whereas much higher concentrations of curcumin were required to inhibit aggregation induced by other platelet agonists. Pretreatment of platelets with curcumin resulted in inhibition of platelet aggregation induced by calcium ionophore A-23187 (IC50; 100 microM), but curcumin up to 250 microM had no inhibitory effect on aggregation induced by the protein kinase C (PKC) activator phorbol myrsitate acetate (1 microM). Curcumin (100 microM) inhibited the A-23187-induced mobilization of intracellular Ca2+ as determined by using fura-2 acetoxymethyl ester. Curcumin also inhibited the formation of thromboxane A2 (TXA2) by platelets (IC50; 70 microM). These results suggest that the curcumin-mediated preferential inhibition of PAF- and AA-induced platelet aggregation involves inhibitory effects on TXA2 synthesis and Ca2+ signaling, but without the involvement of PKC.

Co-activation of Gi and Gq proteins exerts synergistic effect on human platelet aggregation through activation of phospholipase C and Ca2+ signalling pathways

Our previous studies have shown that subthreshold concentrations of two platelet agonists exert synergistic effects on platelet aggregation. Here we studied the mechanism of synergistic interaction of 5-hydroxytryptamine (5-HT) and epinephrine mediated platelet aggregation. We show that 5-HT had no or little effect on aggregation but it did potentiate the aggregation response of epinephrine. The synergistic interaction of 5-HT (1-5 microM) and epinephrine (0.5-2 microM) was inhibited by alpha2-adrenoceptor blocker (yohimbine; IC50= 0.4 microM), calcium channel blockers (verapamil and diltiazem with IC50 of 10 and 48 mM, respectively), PLC inhibitor (U73122; IC50=6 microM) and nitric oxide (NO) donor, SNAP (IC50=1.6 microM)). The data suggest that synergistic effects of platelet agonists are receptor-mediated and occur through multiple signalling pathways including the activation PLC/Ca2+ signalling cascades.

Dual effects of nimesulide, a COX-2 inhibitor, in human platelets

Nimesulide (CAS 51803-78-2) has been shown to exert marked anti-inflammatory effect in several in vivo models of inflammation. Since nimesulide is considered to be a selective inhibitor of COX-2, it has not been studied in detail in relation to its mechanistic effects on platelets, which express COX-1. This study was conducted to investigate the effects of nimesulide in platelet aggregation. We show that nimesulide (1-100 microM) inhibited platelet aggregation induced by adrenaline (20-200 microM). It also inhibited thromboxane A2 (TXA2) formation by platelets at low concentration (IC50; 1 microM). However, much lower concentrations of nimesulide (0.01-0.1 microM) potentiated the aggregatory response of subthreshold concentrations of adrenaline (0.2-2 microM). Such an effect was blocked by Ca2+-channel blockers, verapamil and diltiazem (IC50: 7 and 46 microM, respectively), nitric oxide donor, SNAP (IC50; 2 microM) and cinchonine (10 nM) but not by genistein (up to 10 microM). These results are indicative of the concentration-dependent dual effects of nimesulide on human platelet aggregation. The synergistic effect of low doses of nimesulide and adrenaline seems to be mediated through inhibition of multiple signalling pathways.

The inhibitory effect of cinchonine on human platelet aggregation due to blockade of calcium influx

The Cinchona bark contains alkaloids like quinine, quinidine, cinchonine and cinchonidine. These agents are effective antimalarial drugs and have been used clinically in malaria caused by Plasmodium falciparum. Previous studies show that quinine and quinidine exert effects on cardiovascular system. This study was conducted to examine the effect of cinchonine on human platelet aggregation. The results show that cinchonine inhibited platelet aggregation mediated by platelet agonists, epinephrine (200 microM), ADP (4.3 microM), platelet activating factor (PAF; 800 nM) and collagen (638 nM) but had no effect on arachidonic acid (AA; 0.75 mM). Cinchonine was most effective in inhibiting aggregation induced by platelet activating factor and epinephrine with IC50 values of 125 and 180 microM respectively, however, higher concentrations of cinchonine were required to inhibit aggregation mediated by ADP or collagen (IC50; 300 microM). Pretreatment of platelets with cinchonine inhibited aggregation caused by Ca2+ ionophore, A-23187 (6 microM), in a dose-dependent manner (IC50; 300 microM) indicating an inhibitory effect on Ca2+-signaling cascade. This was supported by measuring [Ca2+]i in platelets loaded with Fura-2AM where cinchonine inhibited the rise in cytosolic Ca2+ mediated by A-23187 (6 microM) or collagen (638 nM). Results show that cinchonine (20 microM) also inhibited aggregation when platelets were pretreated with protein kinase C (PKC) activator, phorbol myristate acetate (PMA; 0.1 microM) in combination with low doses of platelet activating factor (80 nM). Cinchonine, however, had no effect on AA-induced platelet aggregation and thromboxane A2 (TXA2) synthesis in platelets. These results suggest that antiplatelet effects of cinchonine are mediated mainly through inhibition of Ca2+-influx and protein kinase C pathways in platelets.

Muscarinic regulation of intracellular signaling and neurosecretion in gonadotropin-releasing hormone neurons

Agonist activation of cholinergic receptors expressed in perifused hypothalamic and immortalized GnRH-producing (GT1-7) cells induced prominent peaks in GnRH release, each followed by a rapid decrease, a transient plateau, and a decline to below basal levels. The complex profile of GnRH release suggested that acetylcholine (ACh) acts through different cholinergic receptor subtypes to exert stimulatory and inhibitory effects on GnRH release. Whereas activation of nicotinic receptors caused a transient increase in GnRH release, activation of muscarinic receptors inhibited basal GnRH release. Nanomolar concentrations of ACh caused dose-dependent inhibition of cAMP production that was prevented by pertussis toxin (PTX), consistent with the activation of a plasma-membrane Gi protein. Micromolar concentrations of ACh also caused an increase in phosphoinositide hydrolysis that was inhibited by the M1 receptor antagonist, pirenzepine. In ACh-treated cells, immunoblot analysis revealed that membrane-associated G(alpha q/11) immunoreactivity was decreased after 5 min but was restored at later times. In contrast, immunoreactive G(alpha i3) was decreased for up to 120 min after ACh treatment. The agonist-induced changes in G protein alpha-subunits liberated during activation of muscarinic receptors were correlated with regulation of their respective transduction pathways. These results indicate that ACh modulates GnRH release from hypothalamic neurons through both M1 and M2 muscarinic receptors. These receptor subtypes are coupled to Gq and Gi proteins that respectively influence the activities of PLC and adenylyl cyclase/ion channels, with consequent effects on neurosecretion.

An assessment of the potential of protopine to inhibit microsomal drug metabolising enzymes and prevent chemical-induced hepatotoxicity in rodents

The potential of protopine to inhibit microsomal drug metabolising enzymes (MDM E) and prevent paracetamol- and CCl4-induced hepatotoxicity was studied in rats. Paracetamol at the dose of 640 mg kg-1 produced hepatic damage in rats as manifested by the rise in serum levels of aspartate transaminase (AST) and alanine transaminase (ALT) to 972+/-186 and 624+/-131 IU (mean+/-sem; n=10), respectively, compared to respective control values of 101+/-29 and 64+/-18 IU. Pretreatment of rats with protopine (11 mg kg-1, orally twice daily for 2 days) lowered significantly the respective serum AST and ALT levels (P<0.05) to 289+/-52 and 178+/-43 IU. The hepatotoxic dose of CCl4 (1.5 ml kg-1; orally) raised serum AST and ALT levels to 543+/-89 and 387+/-69 IU (mean+/-sem; n=10), respectively, compared to respective control values of 98+/-28 and 56+/-17 IU. The same dose of protopine (11 mg kg-1) was able to prevent significantly (P<0.05), the CCl4-induced rise in serum enzymes and the estimated values of AST and ALT were 168+/-36 and 93+/-28 IU, respectively. Protopine caused prolongation (P<0.05) in pentobarbital (55 mg kg-1)-induced sleep as well as potentiated strychnine-induced toxicity in rats, suggestive of an inhibitory effect on MDME. These results indicate that protopine exhibits anti-hepatotoxic action which may be mediated through inhibition of MDME.

Panic disorder: effective treatment options

Panic disorder is a distressing and debilitating condition with a familial tendency; it may be associated with situational (agoraphobic) avoidance. The diagnosis of panic disorder requires recurrent, unexpected panic attacks and at least one of the following characteristics: persistent concern about having an additional attack (anticipatory anxiety); worry about the implications of an attack or its consequences (e.g., a catastrophic medical or mental consequence) and making a significant change in behavior as a consequence of the attacks. A variety of pharmacologic interventions is available, as are non-pharmacologic cognitive or cognitive-behavioral therapies that have demonstrated safety and efficacy in the treatment of panic disorder. Early detection and thoughtful selection of appropriate first-line interventions can help these patients, who often have been impaired for years, regain their confidence and ability to function in society.