Participation of neuronal nitric oxide synthase in experimental neuropathic pain induced by sciatic nerve transection

Nerve injury leads to a neuropathic pain state that results from central sensitization. This phenomenom is mediated by NMDA receptors and may involve the production of nitric oxide (NO). In this study, we investigated the expression of the neuronal isoform of NO synthase (nNOS) in the spinal cord of 3-month-old male, Wistar rats after sciatic nerve transection (SNT). Our attention was focused on the dorsal part of L3-L5 segments receiving sensory inputs from the sciatic nerve. SNT resulted in the development of neuropathic pain symptoms confirmed by evaluating mechanical hyperalgesia (Randall and Selitto test) and allodynia (von Frey hair test). Control animals did not present any alteration (sham-animals). The selective inhibitor of nNOS, 7-nitroindazole (0.2 and 2 µg in 50 µL), blocked hyperalgesia and allodynia induced by SNT. Immunohistochemical analysis showed that nNOS was increased (48% by day 30) in the lumbar spinal cord after SNT. This increase was observed near the central canal (Rexed’s lamina X) and also in lamina I-IV of the dorsal horn. Real-time PCR results indicated an increase of nNOS mRNA detected from 1 to 30 days after SNT, with the highest increase observed 1 day after injury (1469%). Immunoblotting confirmed the increase of nNOS in the spinal cord between 1 and 15 days post-lesion (20%), reaching the greatest increase (60%) 30 days after surgery. The present findings demonstrate an increase of nNOS after peripheral nerve injury that may contribute to the increase of NO production observed after peripheral neuropathy.

Lack of tolerance for the anti-dyskinetic effects of 7-nitroindazole, a neuronal nitric oxide synthase inhibitor, in rats

7-Nitroindazole (7-NI) inhibits neuronal nitric oxide synthase in vivo and reduces l-DOPA-induced dyskinesias in a rat model of parkinsonism. The aim of the present study was to determine if the anti-dyskinetic effect of 7-NI was subject to tolerance after repeated treatment and if this drug could interfere with the priming effect of l-DOPA. Adult male Wistar rats (200-250 g) with unilateral depletion of dopamine in the substantia nigra compacta were treated with l-DOPA (30 mg/kg) for 34 days. On the 1st day, 6 rats received ip saline and 6 received ip 7-NI (30 mg/kg) before l-DOPA. From the 2nd to the 26th day, all rats received l-DOPA daily and, from the 27th to the 34th day, they also received 7-NI before l-DOPA. Animals were evaluated before the drug and 1 h after l-DOPA using an abnormal involuntary movement scale and a stepping test. All rats had a similar initial motor deficit. 7-NI decreased abnormal involuntary movement induced by l-DOPA and the effect was maintained during the experiment before 7-NI, median (interquartile interval), day 26: 16.75 (15.88-17.00); day 28: 0.00 (0.00-9.63); day 29: 13.75 (2.25-15.50); day 30: 0.5 (0.00-6.25); day 31: 4.00 (0.00-7.13), and day 34: 0.5 (0.00-14.63), Friedman followed by Wilcoxon test,vs day 26, P < 0.05;. The response to l-DOPA alone was not modified by the use of 7-NI before the first administration of the drug (l-DOPA vs time interaction, F1,10 = 1.5, NS). The data suggest that tolerance to the anti-dyskinetic effects of a neuronal nitric oxide synthase inhibitor does not develop over a short-term period of repeated administration. These observations open a possible new therapeutic approach to motor complications of chronic l-DOPA therapy in patients with Parkinson’s disease.

In vivo and in vitro anti-inflammatory and anti-nociceptive activities of lovastatin in rodents

Statins are among the most prescribed drugs in recent clinical practice. They are also known for their pleiotropic actions, which are independent of their lipid-lowering properties. The effect of lovastatin was investigated against carrageenan-induced paw edema in male Wistar rats (200-250 g) and on leukocyte migration, as measured by carrageenan-induced peritonitis in male Swiss mice (20-25 g), which are models of acute inflammation. Lovastatin (administered 1 h prior to carrageenan), at oral doses of 2, 5, and 10 mg/kg, markedly attenuated paw edema formation in rats at the 4th hour after carrageenan injection (25, 43, and 37% inhibition, respectively). Inhibitions of 20, 45 and 80% were observed in the leukocyte migration, as evaluated by carrageenan-induced peritonitis in mice with lovastatin doses of 0.5, 1 and 5 mg/kg, as compared to controls. Furthermore, lovastatin (administered 1 h before initiation) reduced the nociceptive effect of the formalin test in mice, at both phases, at doses of 2, 5, and 10 mg/kg: first phase (51, 65, and 70%, respectively) and second phase (73, 57, and 66% inhibition of licking time, respectively). The anti-nociceptive activity of lovastatin was inhibited by naloxone (3 mg/kg, sc). Lovastatin (0.01, 0.1, and 1 µg/mL) inhibited by 23, 79, and 86%, respectively, the release of myeloperoxidase from human neutrophils. Leukocyte (predominantly neutrophils) infiltration was almost completely reduced by lovastatin treatment, as observed in the model of acute paw edema with hematoxylin and eosin staining. In addition, lovastatin decreased the number of cells expressing tumor necrosis factor-α (TNF-α) and the inducible form of nitric oxide synthase (iNOS) activity. Therefore, the alterations in leukocyte activity and cytokine release could contribute to the anti-inflammatory activity of lovastatin.

The methyl ester of rosuvastatin elicited an endothelium-independent and 3-hydroxy-3-methylglutaryl coenzyme A reductase-independent relaxant effect in rat aorta

The relaxant effect of the methyl ester of rosuvastatin was evaluated on aortic rings from male Wistar rats (250-300 g, 6 rats for each experimental group) with and without endothelium precontracted with 1.0 µM phenylephrine. The methyl ester presented a slightly greater potency than rosuvastatin in relaxing aortic rings, with log IC50 values of -6.88 and -6.07 M, respectively. Unlike rosuvastatin, the effect of its methyl ester was endothelium-independent. Pretreatment with 10 µM indomethacin did not inhibit, and pretreatment with 1 mM mevalonate only modestly inhibited the relaxant effect of the methyl ester. Nω-nitro-L-arginine methyl ester (L-NAME, 10 µM), the selective nitric oxide-2 (NO-2) inhibitor 1400 W (10 µM), tetraethylammonium (TEA, 10 mM), and cycloheximide (10 µM) partially inhibited the relaxant effect of the methyl ester on endothelium-denuded aortic rings. However, the combination of TEA plus either L-NAME or cycloheximide completely inhibited the relaxant effect. Inducible NO synthase (NOS-2) was only present in endothelium-denuded aortic rings, as demonstrated by immunoblot with methyl ester-treated rings. In conclusion, whereas rosuvastatin was associated with a relaxant effect dependent on endothelium and hydroxymethylglutaryl coenzyme A reductase in rat aorta, the methyl ester of rosuvastatin exhibited an endothelium-independent and only slightly hydroxymethylglutaryl coenzyme A reductase-dependent relaxant effect. Both NO produced by NOS-2 and K+ channels are involved in the relaxant effect of the methyl ester of rosuvastatin.

Aging alters the production of iNOS, arginase and cytokines in murine macrophages

The limited amount of information on the primary age-related deficiencies in the innate immune system led us to study the production of inducible nitric oxide synthase (iNOS), arginase, and cytokines in macrophages of young (8 weeks old) and old (72 weeks old) female BALB/c mice. We first evaluated iNOS and arginase inducers on peritoneal (PMΦ) and bone marrow-derived (BMMΦ) macrophages of young BALB/c and C57BL/6 mice, and then investigated their effects on macrophages of old mice. Upon stimulation with lipopolysaccharide (LPS), resident and thioglycolate-elicited PMΦ from young mice presented higher iNOS activity than those from old mice (54.4%). However, LPS-stimulated BMMΦ from old mice showed the highest NO levels (50.1%). Identical NO levels were produced by PMΦ and BMMΦ of both young and old mice stimulated with interferon-γ. Arginase activity was higher in resident and elicited PMΦ of young mice stimulated with LPS (48.8 and 32.7%, respectively) and in resident PMΦ stimulated with interleukin (IL)-4 (64%). BMMΦ of old mice, however, showed higher arginase activity after treatment with IL-4 (46.5%). In response to LPS, PMΦ from old mice showed the highest levels of IL-1α (772.3 ± 51.9 pg/mL), whereas, those from young mice produced the highest amounts of tumor necrosis factor (TNF)-α (937.2 ± 132.1 pg/mL). Only TNF-α was expressed in LPS-treated BMMΦ, and cells from old mice showed the highest levels of this cytokine (994.1 ± 49.42 pg/mL). Overall, these results suggest that macrophages from young and old mice respond differently to inflammatory stimuli, depending on the source and maturity of the cell donors.

Endothelial dysfunction in cardiovascular and endocrine-metabolic diseases: an update

The endothelium plays a vital role in maintaining circulatory homeostasis by the release of relaxing and contracting factors. Any change in this balance may result in a process known as endothelial dysfunction that leads to impaired control of vascular tone and contributes to the pathogenesis of some cardiovascular and endocrine/metabolic diseases. Reduced endothelium-derived nitric oxide (NO) bioavailability and increased production of thromboxane A2, prostaglandin H2 and superoxide anion in conductance and resistance arteries are commonly associated with endothelial dysfunction in hypertensive, diabetic and obese animals, resulting in reduced endothelium-dependent vasodilatation and in increased vasoconstrictor responses. In addition, recent studies have demonstrated the role of enhanced overactivation ofβ-adrenergic receptors inducing vascular cytokine production and endothelial NO synthase (eNOS) uncoupling that seem to be the mechanisms underlying endothelial dysfunction in hypertension, heart failure and in endocrine-metabolic disorders. However, some adaptive mechanisms can occur in the initial stages of hypertension, such as increased NO production by eNOS. The present review focuses on the role of NO bioavailability, eNOS uncoupling, cyclooxygenase-derived products and pro-inflammatory factors on the endothelial dysfunction that occurs in hypertension, sympathetic hyperactivity, diabetes mellitus, and obesity. These are cardiovascular and endocrine-metabolic diseases of high incidence and mortality around the world, especially in developing countries and endothelial dysfunction contributes to triggering, maintenance and worsening of these pathological situations.

Nitric oxide synthesis and biological functions of nitric oxide released from ruthenium compounds

During three decades, an enormous number of studies have demonstrated the critical role of nitric oxide (NO) as a second messenger engaged in the activation of many systems including vascular smooth muscle relaxation. The underlying cellular mechanisms involved in vasodilatation are essentially due to soluble guanylyl-cyclase (sGC) modulation in the cytoplasm of vascular smooth cells. sGC activation culminates in cyclic GMP (cGMP) production, which in turn leads to protein kinase G (PKG) activation. NO binds to the sGC heme moiety, thereby activating this enzyme. Activation of the NO-sGC-cGMP-PKG pathway entails Ca2+ signaling reduction and vasodilatation. Endothelium dysfunction leads to decreased production or bioavailability of endogenous NO that could contribute to vascular diseases. Nitrosyl ruthenium complexes have been studied as a new class of NO donors with potential therapeutic use in order to supply the NO deficiency. In this context, this article shall provide a brief review of the effects exerted by the NO that is enzymatically produced via endothelial NO-synthase (eNOS) activation and by the NO released from NO donor compounds in the vascular smooth muscle cells on both conduit and resistance arteries, as well as veins. In addition, the involvement of the nitrite molecule as an endogenous NO reservoir engaged in vasodilatation will be described.

CPU0213, a novel endothelin type A and type B receptor antagonist, protects against myocardial ischemia/reperfusion injury in rats

The efficacy of endothelin receptor antagonists in protecting against myocardial ischemia/reperfusion (I/R) injury is controversial, and the mechanisms remain unclear. The aim of this study was to investigate the effects of CPU0123, a novel endothelin type A and type B receptor antagonist, on myocardial I/R injury and to explore the mechanisms involved. Male Sprague-Dawley rats weighing 200-250 g were randomized to three groups (6-7 per group): group 1, Sham; group 2, I/R + vehicle. Rats were subjected to in vivo myocardial I/R injury by ligation of the left anterior descending coronary artery and 0.5% sodium carboxymethyl cellulose (1 mL/kg) was injected intraperitoneally immediately prior to coronary occlusion. Group 3, I/R + CPU0213. Rats were subjected to identical surgical procedures and CPU0213 (30 mg/kg) was injected intraperitoneally immediately prior to coronary occlusion. Infarct size, cardiac function and biochemical changes were measured. CPU0213 pretreatment reduced infarct size as a percentage of the ischemic area by 44.5% (I/R + vehicle: 61.3 ± 3.2 vs I/R + CPU0213: 34.0 ± 5.5%, P < 0.05) and improved ejection fraction by 17.2% (I/R + vehicle: 58.4 ± 2.8 vs I/R + CPU0213: 68.5 ± 2.2%, P < 0.05) compared to vehicle-treated animals. This protection was associated with inhibition of myocardial inflammation and oxidative stress. Moreover, reduction in Akt (protein kinase B) and endothelial nitric oxide synthase (eNOS) phosphorylation induced by myocardial I/R injury was limited by CPU0213 (P < 0.05). These data suggest that CPU0123, a non-selective antagonist, has protective effects against myocardial I/R injury in rats, which may be related to the Akt/eNOS pathway.

Contrasting effects of nitric oxide and corticotropin- releasing factor within the dorsal periaqueductal gray on defensive behavior and nociception in mice

The anxiogenic and antinociceptive effects produced by glutamate N-methyl-D-aspartate receptor activation within the dorsal periaqueductal gray (dPAG) matter have been related to nitric oxide (NO) production, since injection of NO synthase (NOS) inhibitors reverses these effects. dPAG corticotropin-releasing factor receptor (CRFr) activation also induces anxiety-like behavior and antinociception, which, in turn, are selectively blocked by local infusion of the CRF type 1 receptor (CRFr1) antagonist, NBI 27914 [5-chloro-4-(N-(cyclopropyl)methyl-N-propylamino)-2-methyl-6-(2,4,6-trichlorophenyl)aminopyridine]. Here, we determined whether i) the blockade of the dPAG by CRFr1 attenuates the anxiogenic/antinociceptive effects induced by local infusion of the NO donor, NOC-9 [6-(2-hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-hexanamine], and ii) the anxiogenic/antinociceptive effects induced by intra-dPAG CRF are prevented by local infusion of Nω-propyl-L-arginine (NPLA), a neuronal NOS inhibitor, in mice. Male Swiss mice (12 weeks old, 25-35 g, N = 8-14/group) were stereotaxically implanted with a 7-mm cannula aimed at the dPAG. Intra-dPAG NOC-9 (75 nmol) produced defensive-like behavior (jumping and running) and antinociception (assessed by the formalin test). Both effects were reversed by prior local infusion of NBI 27914 (2 nmol). Conversely, intra-dPAG NPLA (0.4 nmol) did not modify the anxiogenic/antinociceptive effects of CRF (150 pmol). These results suggest that CRFr1 plays an important role in the defensive behavior and antinociception produced by NO within the dPAG. In contrast, the anxiogenic and antinociceptive effects produced by intra-dPAG CRF are not related to NO synthesis in this limbic midbrain structure.

Phytohemagglutinin improves the development and ultrastructure of in vitro-cultured goat (Capra hircus) preantral follicles

The objective this study was to determine the effect of phytohemagglutinin (PHA) on survival, growth and gene expression in caprine secondary follicles culturedin vitro. Secondary follicles (∼0.2 mm) were isolated from the cortex of caprine ovaries and cultured individually for 6 days in α-MEM+ supplemented with PHA (0, 1, 10, 50, 100, or 200 µg/mL). After 6 days of culture, follicle diameter and survival, antrum formation, ultrastructure and expression of mRNA for FSH receptors (FSH-R), proliferating cell nuclear antigen (PCNA), and neuronal nitric oxide synthase were determined. All treatments maintained follicular survival [α-MEM+ (94.59%); 1 µg/mL PHA (96.43%); 10 µg/mL PHA (84.85%); 50 µg/mL PHA (85.29%); 100 µg/mL PHA (88.57%), and 200 µg/mL PHA (87.50)], but the presence of 10 µg/mL PHA in the culture medium increased the antrum formation rate (21.21%) when compared with control (5.41%, P < 0.05) and ensured the maintenance of oocyte and granulosa cell ultrastructures after 6 days of culture. The expression of mRNA for FSH-R (2.7 ± 0.1) and PCNA (4.4 ± 0.2) was also significantly increased in follicles cultured with 10 µg/mL PHA in relation to those cultured in α-MEM+ (1.0 ± 0.1). In conclusion, supplementation of culture medium with 10 µg/mL PHA maintains the follicular viability and ultrastructure, and promotes the formation of antral cavity after 6 days of culture in vitro.

A combination of methylprednisolone and quercetin is effective for the treatment of cardiac contusion following blunt chest trauma in rats

Cardiac contusion is a potentially fatal complication of blunt chest trauma. The effects of a combination of quercetin and methylprednisolone against trauma-induced cardiac contusion were studied. Thirty-five female Sprague-Dawley rats were divided into five groups (n=7) as follows: sham, cardiac contusion with no therapy, treated with methylprednisolone (30 mg/kg on the first day, and 3 mg/kg on the following days), treated with quercetin (50 mg·kg−1·day−1), and treated with a combination of methylprednisolone and quercetin. Serum troponin I (Tn-I) and tumor necrosis factor-alpha (TNF-α) levels and cardiac histopathological findings were evaluated. Tn-I and TNF-α levels were elevated after contusion (P=0.001 and P=0.001). Seven days later, Tn-I and TNF-α levels decreased in the rats treated with methylprednisolone, quercetin, and the combination of methylprednisolone and quercetin compared to the rats without therapy, but a statistical significance was found only with the combination therapy (P=0.001 and P=0.011, respectively). Histopathological degeneration and necrosis scores were statistically lower in the methylprednisolone and quercetin combination group compared to the group treated only with methylprednisolone (P=0.017 and P=0.007, respectively). However, only degeneration scores were lower in the combination therapy group compared to the group treated only with quercetin (P=0.017). Inducible nitric oxide synthase positivity scores were decreased in all treatment groups compared to the untreated groups (P=0.097, P=0.026, and P=0.004, respectively). We conclude that a combination of quercetin and methylprednisolone can be used for the specific treatment of cardiac contusion.

Hepatic inducible nitric oxide synthase expression increases upon exposure to hypergravity

Stimulation by a number of conditions, including infection, cytokines, mechanical injury, and hypoxia, can upregulate inducible nitric oxide synthase (iNOS) in hepatocytes. We observed that exposure to hypergravity significantly upregulated the transcription of the hepatic iNOS gene. The aim of this study was to confirm our preliminary data, and to further investigate the distribution of the iNOS protein in the livers of mice exposed to hypergravity. ICR mice were exposed to +3 Gz for 1 h. We investigated the time course of change in the iNOS expression. Hepatic iNOS mRNA expression progressively increased in centrifuged mice from 0 to 12 h, and then decreased rapidly by 18 h. iNOS mRNA levels in the livers of centrifuged mice was significantly higher at 3, 6, and 12 h than in uncentrifuged control mice. The pattern of iNOS protein expression paralleled that of the mRNA expression. At 0 and 1 h, weak cytoplasmic iNOS immunoreactivity was found in some hepatocytes surrounding terminal hepatic venules. It was noted that at 6 h there was an increase in the number of perivenular hepatocytes with moderate to strong cytoplasmic immunoreactivity. The number of iNOS-positive hepatocytes was maximally increased at 12 h. The majority of positively stained cells showed a strong intensity of iNOS expression. The expression levels of iNOS mRNA and protein were significantly increased in the livers of mice exposed to hypergravity. These results suggest that exposure to hypergravity significantly upregulates iNOS at both transcriptional and translational levels.

Caryocar brasiliense camb protects against genomic and oxidative damage in urethane-induced lung carcinogenesis

The antioxidant effects of Caryocar brasiliense Camb, commonly known as the pequi fruit, have not been evaluated to determine their protective effects against oxidative damage in lung carcinogenesis. In the present study, we evaluated the role of pequi fruit against urethane-induced DNA damage and oxidative stress in forty 8-12 week old male BALB/C mice. An in vivo comet assay was performed to assess DNA damage in lung tissues and changes in lipid peroxidation and redox cycle antioxidants were monitored for oxidative stress. Prior supplementation with pequi oil or its extract (15 µL, 60 days) significantly reduced urethane-induced oxidative stress. A protective effect against DNA damage was associated with the modulation of lipid peroxidation and low protein and gene expression of nitric oxide synthase. These findings suggest that the intake of pequi fruit might protect against in vivo genotoxicity and oxidative stress.

Hormonal therapy with estradiol and drospirenone improves endothelium-dependent vasodilation in the coronary bed of ovariectomized spontaneously hypertensive rats

Drospirenone (DRSP) is a progestin with anti-aldosterone properties and it reduces blood pressure in hypertensive women. However, the effects of DRSP on endothelium-dependent coronary vasodilation have not been evaluated. This study investigated the effects of combined therapy with estrogen (E2) and DRSP on endothelium-dependent vasodilation of the coronary bed of ovariectomized (OVX) spontaneously hypertensive rats. Female spontaneously hypertensive rats (n=87) at 12 weeks of age were randomly divided into sham operated (Sham), OVX, OVX treated with E2 (E2), and OVX treated with E2 and DRSP (E2+DRSP) groups. Hemodynamic parameters were directly evaluated by catheter insertion into the femoral artery. Endothelium-dependent vasodilation in response to bradykinin in the coronary arterial bed was assessed using isolated hearts according to a modified Langendorff method. Coronary protein expression of endothelial nitric oxide synthase and estrogen receptor alpha (ER-α) was assessed by Western blotting. Histological slices of coronary arteries were stained with hematoxylin and eosin, and morphometric parameters were analyzed. Oxidative stress was assessed in situ by dihydroethidium fluorescence. Ovariectomy increased systolic blood pressure, which was only prevented by E2+DRSP treatment. Estrogen deficiency caused endothelial dysfunction, which was prevented by both treatments. However, the vasodilator response in the E2+DRSP group was significantly higher at the three highest concentrations compared with the OVX group. Reduced ER-α expression in OVX rats was restored by both treatments. Morphometric parameters and oxidative stress were augmented by OVX and reduced by E2 and E2+DRSP treatments. Hormonal therapy with E2 and DRSP may be an important therapeutic option in the prevention of coronary heart disease in hypertensive post-menopausal women.