Effects of calcium channel antagonists on the induction of nitric oxide synthase in cultured cells by immunostimulants

Immunomodulatory properties of antihypertensive drugs and digitalis glycosides

INTRODUCTION

The role of chronic inflammatory process in the pathogenesis or exacerbation of hypertension has been already acknowledged.

AREAS COVERED

Therefore, one can speculate that hypotensive drugs may exert some of their therapeutic effects due to immunomodulatory properties. So far, this assumption has been tested in different studies, and the resulting knowledge is summarized in the current review article that is dedicated to different groups of antihypertensives, namely calcium channel blockers, beta blockers, as well as other less commonly used medications, such as hydralazine, agonists of alfa-2 receptor, diazoxide, doxazosin, aliskiren, and sodium nitroprusside. Articles were found in the Pubmed database by entering the name of a specific drug (or group of drugs) together with the words: immunology, cellular response, humoral response, inflammation, interleukin. The 2000-2021 range was used to search for all drugs except propranolol (1980-2021) and calcium blockers (1990-2021).

EXPERT OPINION

Observed decrease in serum/plasma concentration of proinflammatory cytokines, and CRP along with lower expression of adhesion molecules on immune cells strongly suggest that these drugs possess immunomodulatory properties, which seems to be crucial in the medical practice, especially in the therapy of hypertensive patients with other accompanying inflammatory-based diseases, such as type II diabetes, developed metabolic syndrome, allergies or autoimmunity.

Nitric Oxide Produced by the Antioxidant Activity of Verapamil Improves the Acute Wound Healing Process

BACKGROUND

Verapamil is used in the treatment of hypertension, angina pectoris, cardiac arrhythmia, hypertrophic scars, and keloids to block transmembrane calcium ion flux. Verapamil has antioxidant activity, which enhances the production of nitric oxide (NO). NO promotes the proliferation of fibroblasts, keratinocytes, endothelial cells, and epithelial cells during wound healing. In this study, we investigated the effect of verapamil and its antioxidant properties on the enhancement of acute wound healing via NO.

METHODS

A full-thickness wound healing model was created on the rat dorsal with a silicone ring. The wound closure rate was estimated every 2 days for 14 days. A histological study was performed to evaluate wound healing. Immunofluorescence staining was analyzed for angiogenesis. The expressions of collagen type I (COL I), collagen type III (COL III), and vascular endothelial growth factor (VEGF) were assessed by Western blot. Real-time polymerase chain reaction (qRT-PCR) was performed to examine the expression of endothelial NO synthase and inducible NO synthase, which are related to antioxidant activity in the process of wound healing.

RESULTS

The wound closure rate was faster in the verapamil group compared to the control and silicone groups. Histologic analysis revealed capillaries and stratum basale in the verapamil group. Immunofluorescence staining was shown vessel formation in the verapamil group. Western blot and qRT-PCR analysis revealed high expression levels of COL I, VEGF, eNOS, and FGF in the verapamil.

CONCLUSION

Verapamil's antioxidant activity enhances NO production in acute wound healing. We suggest that verapamil can be used to promote acute wound healing.

A review of the immunologic findings observed in retinitis pigmentosa

Most patients suffering from retinitis pigmentosa (RP) inherit the disorder; however, the immune-pathologic features associated with this disease have yet to be extensively studied. Six reports correlate antiretinal immune activity with vision deterioration in RP patients. Some of these patients have sporadic RP that occurs in excess of expected gene segregation during inheritance. The hypothesis that a primary immune-mediated disease process occurs in this sporadic group is supported by significant associations of RP with autoimmune endocrinopathies and other immune-related conditions or factors; however, no immunologic difference regarding RP family history is reported in the peripheral blood studies of RP patients. Twenty-one percent to 51% of RP patients display antiretinal antibodies, whereas 19-58% have antiretinal lymphocyte reactivity to retinal extract, and 60-85% have activated T cells. Mutations in animal models of RP have been shown to cause endoplasmic reticulum stress that may initiate immunopathology for genetic RP, but oxidative stress also encourages immune cytotoxicity. In addition, necrotic cell death is evident, which promotes inflammatory conditions. We review mechanisms and evidence for an occult inflammation in genetic RP and examine reports of efficacy in retarding RP progression with anti-inflammatory agents in clinical trials.

Using Salivary Nitrite and Nitrate Levels as a Biomarker for Drug-Induced Gingival Overgrowth

Aim: Drug-induced gingival overgrowth has a multifactorial nature and the pathogenesis is still uncertain. It has been suggested that Nitric Oxide (NO) might play a role in the pathogenesis of drug-induced gingival overgrowth due to the contribution of NO to immune response and matrix degradation. NO levels in biological fluids have been used as a diagnostic biomarker in many diseases. The aim of this study is to determine whether NO levels in plasma, saliva, and gingival crevicular fluid (GCF) can serve as a potential biomarker for the evaluation of drug-induced gingival overgrowth risk.

Materials and Methods: A total of 104 patients, receiving cyclosporine A (n = 35), phenytoin (n = 25), nifedipine (n = 26), or diltiazem (n = 18) participated in the study. The amount of gingival overgrowth was evaluated with two indices and was given as percentage. Periodontal clinical parameters including plaque index (PI), gingival index (GI), gingival bleeding time index (GBTI), and probing depth (PD) were also assessed. Saliva, GCF, and plasma samples were obtained from each participants. Nitrite and nitrate levels in saliva, GCF, and plasma were analyzed by Griess reagent.

Results: Salivary nitrite and nitrate levels in responders were significantly higher than those in non-responders in only phenytoin group (p < 0.05). Nitrite and nitrate levels of gingival crevicular fluid and plasma did not significantly differ between responders and non-responders in all study groups (p > 0.05). Salivary nitrite levels exhibited a significant correlation with PD, GBTI, severity of gingival overgrowth (%GO), and GCF volume (p < 0.05). Additionally, a strong positive correlation was detected between saliva and plasma nitrate levels (p < 0.005). However, both nitrite and nitrate levels in GCF and plasma demonstrated no significant correlation with clinical parameters, GO severity, and GCF volume (p > 0.05).

Conclusion: Salivary nitrite and nitrate levels could be used as periodontal disease biomarkers in phenytoin induced gingival overgrowth, and that saliva seems to have a better diagnostic potential than GCF and plasma for the evaluation of drug-induced gingival overgrowth risk. However, when all drug groups were considered, saliva nitrite and nitrate levels could not be used as a biomarker for drug-induced gingival overgrowth.

Relationship between nitric oxide- and calcium-dependent signal transduction pathways in growth hormone release from dispersed goldfish pituitary cells

Nitric oxide (NO) and Ca(2+) are two of the many intracellular signal transduction pathways mediating the control of growth hormone (GH) secretion from somatotropes by neuroendocrine factors. We have previously shown that the NO donor sodium nitroprusside (SNP) elicits Ca(2+) signals in identified goldfish somatotropes. In this study, we examined the relationships between NO- and Ca(2+)-dependent signal transduction mechanisms in GH secretion from primary cultures of dispersed goldfish pituitary cells. Morphologically identified goldfish somatotropes stained positively for an NO-sensitive dye indicating they may be a source of NO production. In 2h static incubation experiments, GH release responses to the NO donor S-nitroso-N-acetyl-d,l-penicillamine (SNAP) were attenuated by CoCl2, nifedipine, verapamil, TMB-8, BHQ, and KN62. In column perifusion experiments, the ability of SNP to induce GH release was impaired in the presence of TMB-8, BHQ, caffeine, and thapsigargin, but not ryanodine. Caffeine-elicited GH secretion was not affected by the NO scavenger PTIO. These results suggest that NO-stimulated GH release is dependent on extracellular Ca(2+) availability and voltage-sensitive Ca(2+) channels, as well as intracellular Ca(2+) store(s) that possess BHQ- and/or thapsigargin-inhibited sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPases, as well as TMB-8- and/or caffeine-sensitive, but not ryanodine-sensitive, Ca(2+)-release channels. Calmodulin kinase-II also likely participates in NO-elicited GH secretion but caffeine-induced GH release is not upstream of NO production. These findings provide insights into how NO actions many integrate with Ca(2+)-dependent signalling mechanisms in goldfish somatotropes and how such interactions may participate in the GH-releasing actions of regulators that utilize both NO- and Ca(2+)-dependent transduction pathways.

Antihypertensive effect of barnidipine 10 mg or amlodipine 5 to 10 mg once daily in treatment-naive patients with essential hypertension: A 24-week, randomized, open-label, pilot study

BACKGROUND

Dihydropyridine calcium antagonists are largely employed for the treatment of hypertension, coronary heart disease, and heart failure.

OBJECTIVE

The aim of our study was to compare the antihypertensive effect of the dihydropyridine calcium antagonists barnidipine and amlodipine.

METHODS

This was a 24-week, randomized, open-label, pilot study. Consecutive treatment-naive patients with grade I or II essential hypertension (office sitting systolic blood pressure [BP] of 140-179 mm Hg and diastolic BP of 90-109 mm Hg) were enrolled. The primary end points were the effect of treatment with either barnidipine 10 mg or amlodipine 5 mg once daily on office and ambulatory BP, left ventricular mass index (LVMI), and markers of cardiac damage, serum procollagen type I C-terminal propeptide, and plasma amino-terminal pro-B-type natriuretic peptide concentrations. Patients were assessed at enrollment, and 12 and 24 weeks. During each visit, the prevalence of adverse events (AEs) was also monitored using spontaneous reporting, patient interview, and physical examination, the relationship to study drug being determined by the investigators. Compliance with treatment was assessed at each study visit by counting returned tablets.

RESULTS

Thirty eligible patients (20 men, 10 women; mean [SD] age, 47 [12] years) were included in the study; all patients completed the 24 weeks of study treatment. Twelve weeks after randomization, 6 patients in the amlodipine group had their dose doubled to 10 mg due to inadequate BP control. Mean BP reductions at study end were not significantly different between the barnidipine and amlodipine groups (office BP, -10.3/-9.4 vs -16.6/-9.1 mm Hg; ambulatory BP, 9.4/6.4 vs 8.1/5.1 mm Hg). Reductions in LVMI and markers of cardiac damage were not significantly different between the 2 groups. Significantly more patients in the amlodipine group reported drug-related AEs compared with those in the barnidipine group (9 [60%] vs 2 [13%]; P < 0.05).

CONCLUSION

In this small sample of treatment-naive hypertensive patients, the antihypertensive effect of barnidipine 10 mg once daily was not significantly different from that of amlodipine 5 to 10 mg once daily.

Recurrent headache as the main symptom of acquired cerebral toxoplasmosis in nonhuman immunodeficiency virus-infected subjects with no lymphadenopathy: the parasite may be responsible for the neurogenic inflammation postulated as a cause of different types of headaches

Headache and/or migraine, a common problem in pediatrics and internal medicine, affect about 5% to 10% children and adolescents, and nearly 30% of middle-aged women. Headache is also one of the most common clinical manifestations of acquired Toxoplasma gondii infection of the central nervous system (CNS) in immunosuppressed subjects. We present 11 apparently nonhuman immunodeficiency virus-infected children aged 7 to 17 years (8 girls, 3 boys) and 1 adult woman with recurrent severe headaches in whom latent chronic CNS T. gondii infection not manifested by enlarged peripheral lymph nodes typical for toxoplasmosis, was found. In 7 patients, the mean serum IgG Toxoplasma antibodies concentration was 189 +/- 85 (SD) IU/mL (range 89 to 300 IU/mL), and in 5 other subjects, the indirect fluorescent antibody test titer ranged from 1:40 to 1:5120 IU/mL (n= <1:10 IU/mL). Some of the patients suffered also from atopic dermatitis (AD) and were exposed to cat and/or other pet allergens, associated with an increased IL-4 and decreased IFN-gamma production. These cytokine irregularities caused limited control of cerebral toxoplasmosis probably because IL-4 down-regulated both the production of IFN-gamma and its activity, and stimulated production of a low NO-producing population of monocytes, which allowed cysts rupture, increased parasite multiplication and finally reactivation of T. gondii infection. The immune studies performed in 4 subjects showed a decreased percentage of T lymphocytes, increased total number of lymphocytes B and serum IgM concentration, and impaired phagocytosis. In addition, few of them had also urinary tract diseases known to produce IL-6 that can mediate immunosuppressive functions, involving induction of the anti-inflammatory cytokine IL-10. These disturbances probably resulted from the host protective immune reactions associated with the chronic latent CNS T. gondii infection/inflammation. This is consistent with significantly lower enzyme indoleamine 2,3-dioxygenase (IDO) activity reported in atopic than in nonatopic individuals, and an important role that IDO and tryptophan degradation pathways plays in both, the host resistance to T. gondii infection and its reactivation. Analysis of literature information on the subjects with different types of headaches caused by foods, medications, and other substances, may suggest that their clinical symptoms and changes in laboratory data result at least in part from interference of these factors with dietary tryptophan biotransformation pathways. Several of these agents caused headache attacks through enhancing NO production via the conversion of arginine to citrulline and NO by the inducible nitric oxide synthase enzyme, which results in the high-output pathway of NO synthesis. This increased production of NO is, however, quickly down-regulated by NO itself because this biomolecule can directly inactivate NOS, may inhibit Ia expression on IFN-gamma-activated macrophages, which would limit antigen-presenting capability, and block T-cell proliferation, thus decreasing the antitoxoplasmatic activity. Moreover, NO inhibits IDO activity, thereby suppressing kynurenine formation, and at least one member of the kynurenine pathway, 3-hydroxyanthranilic acid, has been shown to inhibit NOS enzyme activity, the expression of NOS mRNA, and activation of the inflammatory transcription factor, nuclear factor-kB. In addition, the anti-inflammatory cytokines IL-4 and IL-10, TGF-beta, and a cytokine known as macrophage deactivating factor, have been shown to directly modulate NO production, sometimes expressing synergistic activity. On the other hand, IL-4 and TGF-beta can suppress IDO activity in some cells, for example human monocytes and fibroblasts, which is consistent with metabolic pathways controlled by IDO being a significant contributor to the proinflammatory system. Also, it seems that idiopathic intracranial hypertension, pseudotumor cerebri, and aseptic meningitis, induced by various factors, may result from their interference with IDO and inducible nitric oxide synthase activities, endogenous NO level, and cytokine irregularities which finally affect former T. gondii status 2mo in the brain. All these biochemical disturbances caused by the CNS T. gondii infection/inflammation may also be responsible for the relationship found between neurologic symptoms, such as headache, vertigo, and syncope observed in apparently immunocompetent children and adolescents, and physical and psychiatric symptoms in adulthood. We therefore believe that tests for T. gondii should be performed obligatorily in apparently immunocompetent patients with different types of headaches, even if they have no enlarged peripheral lymph nodes. This may help to avoid overlooking this treatable cause of the CNS disease, markedly reduce costs of hospitalization, diagnosis and treatment, and eventually prevent developing serious neurologic and psychiatric disorders.

Comparative effects of azelnidipine and other Ca2+-channel blockers on the induction of inducible nitric oxide synthase in vascular smooth muscle cells

Overproduction of nitric oxide by inducible nitric oxide synthase contributes to the progression of cardiovascular disease. We investigated the effects of azelnidipine and other Ca2+-channel blockers on nitric oxide production by cultured aortic smooth muscle cells isolated from Wistar rats and human umbilical vein endothelial cells (HUVECs), using the Griess reaction and oxyhemoglobin method. Release of lactic dehydrogenase (LDH) was measured to evaluate cell damage, and immunohistochemistry was performed to examine the expression of inducible nitric oxide synthase and nitrotyrosine protein. Azelnidipine and other Ca2+-channel blockers inhibited the release of nitric oxide induced by lipopolysaccharide plus interferon-gamma. Azelnidipine inhibited it most potently among the Ca2+-channel blockers tested (azelnidipine, amlodipine, nifedipine, diltiazem, verapamil, and nicardipine) at a concentration of 10 microM. Longer stimulation with these agents induced the expression of inducible nitric oxide synthase and nitrotyrosine, with an increase of lactic dehydrogenase release, whereas azelnidipine suppressed these changes. In human umbilical vein endothelial cells, azelnidipine enhanced basal nitric oxide production by endothelial nitric oxide synthase. In conclusion, azelnidipine potently inhibited the induction of inducible nitric oxide synthase and then nitric oxide production in vascular smooth muscle cells, while enhancing constitutive nitric oxide production by endothelial cells. Azelnidipine may inhibit nitrotyrosine expression and cell damage caused by overproduction of nitric oxide, suggesting a mechanism for its cardiovascular protective effect.

Effect of Cyclosporin A on the Expression of Inducible Nitric Oxide Synthase in the Gingiva of Rats

BACKGROUND

The role of nitric oxide (NO) in the pathogenesis of cyclosporin A (CsA)-induced gingival overgrowth is still unknown. The purpose of this study was to evaluate the effect of CsA on the expression of nitric oxide synthases (NOS) in the gingival tissue of rats.

METHODS

Thirty male Sprague-Dawley rats were randomly assigned to a control and two test groups. Rats in each group received CsA (0, 10, or 30 mg/kg) daily by gastric feeding for 4 weeks. The plasma NO and the NOS enzyme activities were assayed at week 4 in the blood samples and in the gingiva and lung tissue specimens, respectively. The distribution of inducible nitric oxide synthase (iNOS) was further evaluated in tissues obtained from the gingiva and lung at the end of weeks 1 and 4 by immunohistochemistry.

RESULTS

In the CsA-treated animals, increased levels of plasma nitrites/nitrates were measured in comparison to those in control rats. Significantly greater iNOS enzyme activities were detected in lung and gingival tissues obtained from CsA-treated animals than from control animals. In addition, cells positively staining for iNOS were clearly observed in both gingival and lung tissues obtained from the CsA-treated animals by immunohistochemistry, whereas a few stained cells were found in those from the control group. The quantity of cells positively stained for iNOS was greater in tissue from week 4 than week 1.

CONCLUSIONS

The effect of CsA on gingival iNOS expression was evaluated in rats for 4 weeks. A greater iNOS expression in the gingiva was observed after CsA therapy by both enzyme activities and immunohistochemica staining. Therefore, we suggest that CsA can increase gingival iNOS expression, which may play an important role in cyclosporin-induced gingival overgrowth.

Amlodipine inhibits pro-inflammatory cytokines and free radical production and inducible nitric oxide synthase expression in lipopolysaccharide/interferon-gamma-stimulated cultured vascular smooth muscle cells

Overproduction of nitric oxide (NO) from inducible nitric oxide synthase (iNOS) is importantly involved in the pathogenesis of endotoxemia and atherosclerosis. Calcium antagonists are commonly used as cardiovascular drugs and have a beneficial effect on prolonging survival in various models of endotoxin shock. The present study was to investigate the effect of a calcium antagonist amlodipine on nitrite, tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) formation and iNOS induction both in lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma)-treated rat aortic smooth muscle cells (RASMC) and in a rat model of endotoxemia. Incubation with amlodipine (0.1 - 10 microM) for 24 h resulted in a significant and dose-dependent attenuation in medium nitrite, TNF-alpha and IL-1beta formation as well as iNOS protein expression in LPS/IFN-gamma-treated RASMC. In addition, amlodipine inhibited leucigenin-induced superoxide formation in RASMC. In the rat endotoxic model, the serum nitrite/nitrate, TNF-alpha and IL-1beta levels as well as iNOS protein expression of lungs were also suppressed by administration of amlodipine (50 microg/kg, i.v.). These results suggest that amlodipine may exert vascular beneficial effects by suppressing pro-inflammatory cytokines and free radical generation as well as iNOS induction in smooth muscle cells during activation of inflammatory mechanism.

Amlodipine increases nitric oxide synthesis in cytokine-stimulated cultured vascualar smooth muscle cells

OBJECTIVE

If calcium channel blockers affect nitric oxide synthesis in the vascular tissue, they could influence disease progression in coronary arteries. We investigated the effects of the calcium channel blocker amlodipine on nitric oxide synthesis by measuring the production of nitrite, a stable metabolite of nitric oxide, in vascular smooth muscle cells.

METHODS

We measured the production of nitrate in cultured rat vascular smooth muscle cells with the Griess reagent Inducible nitric oxide synthase protein and mRNA expression were assayed by Western blotting and reverse transcription-polymerase chain reaction, respectively. The levels of NF-kappaB proteins in nuclear extracts were analyzed by gel retardation assay.

RESULTS

Incubation of cultures with interleukin-1 , (10 ng/ ml) for 24 h caused a significant increase in nitrite generation. Interleukin-1 l-induced nitrite production by vascular smooth muscle cells was significantly increased by amlodipine in a dose-dependent manner. This augmentative effect of amlodipine was completely abolished in the presence of N(G)-monomethyl-L-arginine or actinomycin D. Amlodipine-induced nitrite production was accompanied by increased inducible nitric oxide synthase mRNA and protein accumulation. Interleukin-1 , induced NF-kappaB activation in vascular smooth muscle cells, and addition of amlodipine further increased this NF-kappaB activation. The effect of amlodipine on nitrite production was maintained in the presence of the calcium channel agonist Bay K 8644.

CONCLUSION

Amlodipine enhances nitric oxide synthesis in cytokine-stimulated cultured vascular smooth muscle cells by L-type calcium channel-independent mechanisms.

Regulation of inducible nitric oxide synthase gene expression in vascular smooth muscle cells

1. Formation of nitric oxide (NO) by the constitutive calcium-dependent NO synthase expressed in endothelial cells plays an important role in the control of local blood flow and vascular homeostasis. Expression of the inducible calcium-independent NO synthase (iNOS) in vascular smooth muscle cells (VSMC), on the other hand, is thought to play a potentially detrimental role in the pathogenesis of chronic inflammation or septic shock. In vascular injury, however, iNOS expression in VSMC may be beneficial as a compensatory mechanism for the lack of endothelial NO synthesis, e.g., by preventing restenosis following angioplasty or heart transplant vasculopathy. 2. Because iNOS activity does not seem to be controlled once the enzyme is expressed, regulation of NO release from iNOS-expressing cells predominantly occurs at the transcriptional and/or posttranscriptional level. 3. This review summarizes what is currently known about the regulation of expression of this enzyme in VSMC, details some of the transcription factors involved therein as well as their mode of activation, and highlights some pharmacological strategies based on these findings that may be employed for the control of iNOS expression in VSMC in the clinical arena.

Felodipine inhibits free-radical production by cytokines and glucose in human smooth muscle cells

An imbalance between nitric oxide (NO) and superoxide is importantly involved in the pathogenesis of vascular disease. Inflammatory stimuli and risk factors contribute to these alterations. Calcium antagonists and angiotensin-converting enzyme inhibitors are commonly used cardiovascular drugs. To clarify the effect of felodipine and ramiprilat on the balance of these free radicals, we stimulated human aortic smooth muscle cells (HASCs) with cytokines (human interleukin-1beta, tumor necrosis factor-alpha, lipopolysaccharide, and/or interferon-gamma) or high glucose in the presence and absence of these compounds. Felodipine, but not ramiprilat, concentration-dependently inhibited cytokine-induced NO production and NO synthase (NOS) mRNA induction. The antioxidant N-acetylcysteine also inhibited cytokine-induced NO production and induction of inducible NOS mRNA. Moreover, felodipine inhibited cytokine-induced superoxide production both in the presence and absence of an NOS inhibitor, suggesting that it acted as a superoxide scavenger and not as an inhibitor of inducible NOS induction. High glucose treatment (22 mmol/L for 48 hours) also significantly increased superoxide production in HASCs, and this increase was inhibited in a concentration-dependent manner by felodipine but not by ramiprilat. These results suggest that felodipine may exert vascular protective effects by suppressing free radical generation in human smooth muscle cells during activation of inflammatory mechanisms and diabetic conditions.

Dantrolene inhibits nitric oxide synthase in rat alveolar macrophages treated with lipopolysaccharide and interferon-gamma

PURPOSE

To examine the effects of dantrolene on nitric oxide (NO) production and on the activity and protein expression of inducible nitric oxide synthase (iNOS) induced by lipopolysaccharide (LPS) plus interferon-gamma (IFN gamma) in rat alveolar macrophages.

METHODS

Pulmonary alveolar macrophages isolated from Sprague-Dawley rats were used. After incubation of macrophages with dantrolene (1 to 100 microM) and LPS (1 microgram.ml-1) and IFN-gamma (100 u.ml-1) for 24 hr, the cell-free medium was removed for measuring the nitrite and tumour necrosis factor-alpha (TNF-alpha) levels by Griess reaction and ELISA kit, respectively. The harvested macrophages were also used to determine the activity of iNOS by using the conversion of [3H]-L-arginine to [3H]-L-citrulline method. Protein expression of iNOS was detected by Western blot analysis.

RESULTS

In rats alveolar macrophages, (i) dantrolene (1 to 100 microM) caused a dose-dependent suppression of the production of nitrite and TNF-alpha induced by LPS (1 microgram.ml-1) plus IFN-gamma (100 u.ml-1) and (ii) dantrolene (100 microM) inhibited the activity (by 37 +/- 5%, P < 0.01) and protein expression (by 39 +/- 12%, P < 0.01) of iNOS in response to LPS plus IFN-gamma.

CONCLUSION

Dantrolene inhibits NO production as well as the activity and expression of iNOS in alveolar macrophages treated with LPS plus IFN-gamma, which may be associated with the reduction of TNF-alpha production.

Ketamine inhibits nitric oxide synthase in lipopolysaccharide-treated rat alveolar macrophages

PURPOSE

To evaluate the effects of ketamine on the activity and protein expression of inducible nitric oxide synthase (iNOS) induced by lipopolysaccharide (LPS) in rat alveolar macrophages.

METHODS

Pulmonary alveolar macrophages isolated from Wistar-Kyoto rats were used. After incubation of macrophages with ketamine (1, 10, or 100 microM) and LPS (1 microgram.ml-1) for 24 hr, the cell-free medium was removed for measuring the nitrite and tumour necrosis factor-alpha (TNF-alpha) levels by Griess reaction and ELISA kit, respectively. The harvested macrophages were also used to determine the activity of iNOS by using the conversion of [3H]-L-arginine to [3H]-L-citrulline method. In addition, the protein expression of iNOS was detected by Western blot analysis.

RESULTS

In rat alveolar macrophages, (i) ketamine (1 to 100 microM) caused a dose-dependent suppression of the production of nitrite and TNF-alpha induced by LPS and (ii) ketamine (100 microM) inhibited the activity (46.5 +/- 4.8%, P < 0.05) and protein expression (35 +/- 11%, P < 0.05) of iNOS in response to LPS.

CONCLUSION

These results show that ketamine inhibits the activity and expression of iNOS in LPS-activated alveolar macrophages, which may be associated with the reduction of the release of TNF-alpha following LPS treatment.

Nitric oxide and shock

Shock can be defined as the failure of the circulatory system to provide necessary cellular nutrients, including oxygen, and to remove metabolic wastes. Although it is now recognized that more than 100 different forms of shock exist, this recognition is more a reflection of the widespread use of the term to describe a variety of disease states. For the purpose of this monograph, we concentrate on various forms of cardiovascular shock, in particular, shock that may be linked to inappropriate vasodilation from overproduction of the endogenous vasodilator, nitric oxide. Some forms of shock have been extensively studied, and convincing evidence exists for the role of nitric oxide. Other disease states have been less well characterized in terms of their association with excess nitric oxide production. Available evidence of a role for nitric oxide is discussed in the hope of stimulating the interest of investigators to explore these areas more thoroughly.