The involvement of nitric oxide in the antinociception induced by cyclosporin A in mice

Cyclosporin A attenuating morphine tolerance through inhibiting NO/ERK signaling pathway in human glioblastoma cell line: the involvement of calcineurin

Cyclosporin A (CsA) is known to have an immunosuppressive action. However, it is also attracting attention due to its effects on the nervous system, such as inhibiting the development and expression of morphine-induced tolerance and dependence through unknown mechanisms. It has been shown that CsA modulates the nitric oxide (NO) synthesis and extracellular signal-regulated kinases (ERK) activation, which are potentially involved in signaling pathways in morphine-induced tolerance in cellular models. Therefore, the current study was designed to evaluate the modulatory role of CsA on the MOR tolerance, by targeting the downstream signaling pathway of NO and ERK using an in vitro model. For this purpose, T98G cells were pretreated with CsA, calcineurin autoinhibitory peptide (CAIP), and N^G-nitro-l-arginine methyl ester (L-NAME) 30 min before 18 h exposure to MOR. Then, we analyzed the intracellular cyclic adenosine monophosphate (cAMP) levels and also the expression of phosphorylated ERK and nitric oxide synthase (nNOS) proteins. Our results showed that CsA (1 nM, 10 nM, and 100 nM) and CAIP (50 µM) have significantly reduced cAMP and nitrite levels as compared to MOR-treated (2.5 µM) T98G cells. This clearly revealed the attenuation of MOR tolerance by CsA. The expression of nNOS and p-ERK proteins were down-regulated when the T98G cells were pretreated with CsA (1 nM, 10 nM, and 100 nM), CAIP (50 µM), and L-NAME (0.1 mM) as compared to MOR. In conclusion, the CsA pretreatment had a modulatory role in MOR-induced tolerance, which was possibly mediated through NO/ERK signaling pathway.

Involvement of the nitric oxide/(C)GMP/K(ATP) pathway in antinociception induced by exercise in rats

AIMS

Physical exercise is responsible for increasing the nociceptive threshold. The present study aimed to investigate the involvement of the nitric oxide/(C)GMP/K(ATP) pathway in antinociception induced by acute aerobic exercise (AAc) in rats.

MAIN METHODS

Wistar rats performed exercise in a rodent treadmill, according to an AAc protocol. The nociceptive threshold was measured by mechanical and thermal nociceptive tests (paw-withdrawal, tail-flick and face-flick). To investigate the involvement of the NO/(C)GMP/K(ATP) pathway the following nitric oxide synthase (NOS) unspecific and specific inhibitors were used: N-nitro-l-arginine (NOArg), Aminoguanidine, N(5)-(1-Iminoethyl)-l-ornithine dihydrocloride (L-NIO), N(omega)-Propyl-l-arginine (L-NPA); guanylyl cyclase inhibitor, 1H-[1,2,4]oxidiazolo[4,3-a]quinoxalin-1-one (ODQ); and K(ATP) channel blocker, Glybenclamide; all administered subcutaneously at a dose of 2mg/kg 10min before exercise started. Plasma and cerebrospinal fluid (CSF) nitrite levels were determined by spectrophotometry.

KEY FINDINGS

In the paw-withdrawal, tail-flick and face-flick tests, the AAc protocol produced antinociception, which lasted for more than 15min. This effect was significantly reversed (P<0.05) by NOS specific and unspecific inhibitors, guanylyl cyclase inhibitor (ODQ) and K(ATP) channel blocker (Glybenclamide). Acute exercise was also responsible for increasing nitrite levels in both plasma and cerebrospinal fluid.

SIGNIFICANCE

Taken together, these results suggest that the NO/(C)GMP/K(ATP) pathway participates in antinociception induced by exercise.

Seizure susceptibility alteration through 5-HT(3) receptor: modulation by nitric oxide

There is some evidence that epileptic seizures could be induced or increased by 5-hydroxytryptamine (5-HT) attenuation, while augmentation of serotonin functions within the brain (e.g. by SSRIs) has been reported to be anticonvulsant. This study was performed to determine the effect of selective 5-HT(3) channel/receptor antagonist granisetron and agonist SR57227 hydrochloride on the pentylenetetrazole (PTZ)-induced seizure threshold in mice. The possible interaction of this effect with nitrergic system was also examined using the nitric oxide (NO) synthase inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME) and the NO precursor l-arginine. SR57227 (10mg/kg, i.p.) significantly increased the seizure threshold compared to control group, while high dose granisetron (10mg/kg, i.p.) proved proconvulsant. Co-administration of sub-effective doses of the 5-HT(3) agonist with l-NAME (5 and 60mg/kg, i.p., respectively) exerted a significant anticonvulsive effect, while sub-effective doses of granisetron (3mg/kg) was observed to have a proconvulsive action with the addition of l-arginine (75mg/kg, i.p.). Our data demonstrate that enhancement of 5-HT(3) receptor function results in as anticonvulsant effect in the PTZ-induced seizure model, and that selective antagonism at the 5-HT(3) receptor yields proconvulsive effects. Furthermore, the NO system may play a role in 5-HT(3) receptor function.

Methotrexate and cyclosporine treatments modify the activities of dipeptidyl peptidase IV and prolyl oligopeptidase in murine macrophages

Analysis of the effects of cyclosporine A (25–28 mgkg⁻¹) and/or methotrexate (0.1 mgkg⁻¹) treatments on dipeptidyl peptidase IV (DPPIV) and prolyl oligopeptidase (POP) activities and on algesic response in two distinct status of murine macrophages (Mφs) was undertaken. In resident Mφs, DPPIV and POP were affected by neither individual nor combined treatments. In thioglycolate-elicited Mφs, methotrexate increased DPPIV (99–110%) and POP (60%), while cyclosporine inhibited POP (21%). Combined treatment with both drugs promoted a rise (51–84%) of both enzyme activities. Only cyclosporine decreased (42%) the tolerance to algesic stimulus. Methotrexate was revealed to exert prevalent action over that of cyclosporine on proinflammatory Mφ POP. The opposite effects of methotrexate and cyclosporine on POP activity might influence the availability of the nociceptive mediators bradykinin and substance P in proinflammatory Mφs. The exacerbated response to thermally induced algesia observed in cyclosporine-treated animals could be related to upregulation of those mediators.

Effect of cyclosporin A on morphine-induced place conditioning in mice: involvement of nitric oxide

Cyclosporin A is shown to attenuate antinociceptive effects of morphine, development and expression of morphine-induced tolerance and dependency via nitric oxide (NO) pathway. In the present study, the effect of systemic cyclosporin A on morphine-induced conditioned place preference (CPP) and the probable involvement of nitric oxide were assessed in mice. Our data showed that administration of morphine (1, 2.5, 5, 7.5, 10 mg/kg) significantly increased the time spent in the drug-paired compartment in a dose-dependent manner. The maximum response was obtained with 5 mg/kg of morphine. Cyclosporin A (5, 10 mg/kg) and N(G)-nitro-L-arginine methyl ester (L-NAME; 2.5, 5, 10 mg/kg), a nonselective nitric oxide synthase (NOS) inhibitor, did not induce either conditioned place preference or conditioned place aversion (CPA), while cyclosporin A (20 mg/kg) induced CPA. Both cyclosporin A (10, 20 mg/kg) and L-NAME (5, 10 mg/kg), in combination with morphine (5 mg/kg) during conditioning, significantly suppressed acquisition of morphine-induced place preference. Lower and per se noneffective doses of Cyclosporin A (1, 2.5, 5 mg/kg) and L-NAME (2.5 mg/kg), when coadministered, exerted a significant potentiating effect on the attenuation of morphine-induced place preference. Aminoguanidine (50, 100 mg/kg), the specific inducible nitric oxide synthase (iNOS) inhibitor, whether alone or in combination with cyclosporin A failed to show this inhibitory effect on morphine-induced place preference. In conclusion, decreasing nitric oxide production through inhibiting constitutive nitric oxide synthase may be a mechanism through which cyclosporin A attenuates morphine-induced place preference.

Cyclosporine-A treatment prevents apoptosis in rat lumbar ganglion cells

We evaluated the expression of pro-apoptotic Bax and anti-apoptotic Bcl-2 in lumbar ganglion cells of rats by immunohistochemistry under normal conditions and after 7, 14 and 21 days of cyclosporine-A treatment (7 and 15 mg/kg/daily). In normal rats, Bax was weakly expressed in all types of neurons, whereas satellite cells showed moderate immunostaining. Bcl-2 expression was weak in type A neurons and weak or moderate in type B and C neurons and also into satellite cells. In cyclosporine-A-treated rats, we found changes in Bax staining of neurons: type A neurons and type B neurons were weakly stained, whereas type C neurons were moderately stained. Bax expression in satellite cells was moderate after 7 days of treatment and increased strongly after 14 and 21 days of treatment. Bcl-2 expression increased significantly in neurons after 14 and even more after 21 days of treatment with 7 mg/kg cyclosporine-A, mainly in type B and C neurons. With 15 mg/kg cyclosporine-A, Bcl-2 increased moderately in type A and B neurons and strongly in type C neurons only after 7 days. After 14 and 21 days, Bcl-2 expression was moderate in type A neurons whereas it was strong or even very strong in type B and C neurons. Satellite cells showed a moderate increase in Bcl-2 after 7 and 14 days of treatment whereas after 21 days, expression was strong. We conclude that (1) in normal conditions, Bax and Bcl-2 were differently expressed in neurons and satellite cells; (2) cyclosporine-A treatment rapidly enhanced Bax expression in satellite cells only, whereas Bcl-2 expression increased moderately in type A neurons and was strongly expressed in type B and C neurons; (3) cyclosporine-A has a protective role in neurons but not in satellite cells; and (4) the neuroprotective role of cyclosporine-A is dose dependent. Furthermore, the strong expression of Bax in satellite cells can explain the temporary nature of the neurotoxic effect commonly observed after cyclosporine-A administration.

Inhibition by immunophilin ligands of morphine-induced tolerance and dependence in guinea pig ileum

Immunophilin ligands, cyclosporine A and FK506 (tacrolimus), besides their immunosuppressive action, have several effects on different neural functions, such as modulation of the release of many neurotransmitters, the reduction of nitric oxide (NO) production by the inhibition of dephosphorylation of neuronal nitric oxide synthase (nNOS) and the alteration of the expression of certain genes. Many of these actions apparently occur through the inhibition of calcineurin, a calcium-calmodulin-dependent phosphatase. On the other hand, several studies have shown that NO has a critical role in opioid-induced tolerance and dependence in both in vivo and in vitro models. In the present study, the effect of cyclosporine A and FK506 on the development of tolerance to and dependence on morphine in the guinea pig ileum was assessed. Morphine inhibited electrically stimulated twitch of ileum in a concentration-dependent manner (pD(2)=7.45+/-0.07). Tolerance to this effect was induced by incubation of ileum with 2 x IC(50) or 4 x IC(50) of morphine for 2 h that induced a degree of tolerance of 6.81 and 18.10, respectively. The co-incubation of ileum with morphine along with either cyclosporine A or FK506 reduced the degree of tolerance significantly (P<0.05) and restored the sensitivity of ileum to the morphine inhibitory effect. Dependence was induced by incubation with 4 x IC(50) of morphine for 2 h and was assessed based on naloxone-induced contractions (10(-5) M). Cyclosporine A (10(-9) M) and FK506 (10(-9) M) can attenuate the development of dependence to morphine as shown by the significant decrease in naloxone-induced contractions (P<0.05). These results suggest that immunophilin ligands at very low concentrations (nanomolar) can reduce the induction of acute tolerance to and dependence on morphine in the myenteric plexus of guinea pig ileum.

The effects of FK506 on the development and expression of morphine tolerance and dependence in mice

FK506 is an immunophilin-binding ligand that inhibits calcineurin and decreases nitric oxide (NO) production in the nervous tissues. We examined the effects in mice of systemic treatment with FK506 on the induction and expression of morphine (s.c.) tolerance and dependence and compared them with the effects of the non-specific NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), and specific inducible NO synthase inhibitor, aminoguanidine. FK506 (0.5-10 mg/kg, s.c.) exerted inhibitory effects on both development and expression of tolerance to morphine-induced antinociception. FK506 also significantly decreased the expression of morphine dependence, as assessed by naloxone-precipitated (2 mg/kg, i.p.) withdrawal syndrome, but a similar effect was not found for the development of morphine dependence. A similar pattern of effects was observed with L-NAME (3-20 mg/kg, i.p.), while aminoguanidine (50-100 mg/kg, i.p.) did not alter tolerance or dependence. Examining the possible interaction between their inhibitory effects on tolerance and dependence, we combined the subeffective doses of FK506 (0.5 or 1 mg/kg) with L-NAME (3 mg/kg) or aminoguanidine (100 mg/kg). The combination of FK506 with L-NAME, but not with aminoguanidine, significantly decreased the development and expression of tolerance and expression of dependence. These data show the effectiveness of FK506 on morphine tolerance and dependence and suggest an additive effect between FK506 and the inhibition of constitutive NO synthesis in this regard.

Evidences for involvement of nitric oxide in the gastroprotective effect of bromocriptine and cyclosporin A on water immersion stress-induced gastric lesions

Previous studies have been shown that the adrenergic system involves in gastric secretion and pathogenesis of peptic lesion and activation of alpha(2)-adrenoceptors located on the vagus nerve inhibits gastric acid secretion. Bromocriptine, a dopamine receptor agonist, also has alpha(2) agonistic effect and prevents indomethacin-induced gastric ulcer. alpha(2)-Adrenoceptors involve in the release of nitric oxide which has cytoprotective activity in gastric mucosa. Cyclosporin A (CsA) has also been suppressed stress-induced gastric mucosal lesions, dose dependently. The object of this study was to clarify the interaction between the anti-ulcer effect of bromocriptine (2, 4, 8 mg kg(-1)) or cyclosporin A (5, 10, 20 mg kg(-1)) and nitric oxide. Intraperitoneal injections of bromocriptine and cyclosporin A prevented water immersion stress-induced gastric ulcer in rats. L-Nitro-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, increased stress-induced lesions while L-arginine, a precursor of nitric oxide, decreased these lesions. In conclusion, increasing level of nitric oxide by bromocriptine and cyclosporin A may be one of the contributory factors in their protective effects on gastric mucosa.