Nitric oxide-based possibilities for pharmacotherapy

Cardiovascular characterization of the novel organic mononitrate NDIBP in rats

Organic nitrates are widely used to restore endogenous nitric oxide (NO) levels reduced by endothelial nitric oxide synthase dysfunction. However, these drugs are associated with undesirable side effects, including tolerance. This study aims to investigate the cardiovascular effects of the new organic nitrate 1,3-diisobutoxypropan-2-yl nitrate (NDIBP). Specifically, we assessed its effects on blood pressure, vascular reactivity, acute toxicity, and the ability to induce tolerance. In vitro and ex vivo techniques showed that NDIBP released NO both in a cell-free system and in isolated mesenteric arteries preparations through a process catalyzed by xanthine oxidoreductase. NDIBP also evoked endothelium-independent vasorelaxation, which was significantly attenuated by 2-phenyl-4,4,5,5,-tetramethylimidazoline-1-oxyl 3-oxide (PTIO, 300 μM), a nitric oxide scavenger; 1-H-[1,2,4] oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ, 10 μM), a soluble guanylyl cyclase inhibitor; tetraethylammonium (TEA, 3 mM), a potassium channel blocker; febuxostat (500 nM), a xanthine oxidase inhibitor; and proadifen (10 μM), an inhibitor of cytochrome P450 enzyme. Furthermore, this organic nitrate did not induce tolerance in isolated vessels and presented low toxicity following acute oral administration. In vivo changes on cardiovascular parameters were assessed using normotensive and renovascular hypertensive rats. NDIBP evoked a reduction of blood pressure that was significantly higher in hypertensive animals. Our results suggest that NDIBP acts as a NO donor, inducing blood pressure reduction without having the undesirable effects of tolerance. Those effects seem to be mediated by activation of NO-sGC-cGMP pathway and positive modulation of K+ channels in vascular smooth muscle.

Design, Synthesis and Biological Evaluation of Nitrate Derivatives of Sauropunol A and B as Potent Vasodilatory Agents

A group of nitrate derivatives of naturally occurring sauropunol A and B were designed and synthesized. Nitric oxide (NO) releasing capacity and vasodilatory capacity studies were performed to explore the structure-activity relationship of resulted nitrates. Biological evaluation of these compounds revealed that most of the synthesized mononitrate derivatives demonstrated superior releasing capacity than isosorbide mononitrate (ISMN), and 2MNS-6 even demonstrated stronger NO releasing capacity than isosorbide dinitrate (ISDN). Two dinitrates, DNS-1 and DNS-2, showed higher NO releasing capacity than ISDN. Evaluation of inhibitory activities to the contractions in mesenteric artery rings revealed that 2MNS-8 and DNS-2 showed stronger vasorelaxation activities than ISDN. High level of NO and soluble guanylyl cyclase (sGC) may be essential for the potent vasodilatory effect of DNS-2. The vasodilatory effects of DNS-2 may result from cellular signal transduction of NO-sGC-cGMP. DNS-2 was found to be the most potent sauropunol-derived nitrate vasodilatory agent for further pharmaceutical investigation against cardiovascular diseases.

Alliin, a garlic organosulfur compound, ameliorates gut inflammation through MAPK-NF-κB/AP-1/STAT-1 inactivation and PPAR-γ activation

SCOPE

In this study, the anti-inflammatory effects and the molecular mechanism of alliin were analyzed in dextran sulfate sodium (DSS)-induced colitis mice and lipopolysaccharide-stimulated RAW264.7 cell model.

METHODS

The phenotype of mice was recorded in the DSS-induced and/or alliin (500 mg/kg) groups. Histopathological alterations were analyzed by H&E staining. MPO and MDA of colon tissues were measured. The mRNA expression levels of inflammatory factors were determined by qRT-PCR, and protein expressions of inflammatory factors or activation of kinases were determined by Western blotting.

RESULTS

Oral administration of alliin significantly inhibited the decrease of body weight, improved the DAI and decreased the infiltration of inflammatory cells in colonic tissues. The content of NO, MDA, and MPO, the expression of iNOS and inflammatory factors as well as MAPK and the phosphorylation of PPAR-γ were inhibited in alliin-treated group. Treatment with alliin significantly repressed the expression of inflammatory factors in LPS-stimulated RAW264.7 cells. Further research demonstrated that alliin repressed LPS-induced AP-1/NF-κB/STAT-1 activation by inhibiting the phosphorylations of p38, JNK, and ERK1/2-regulated PPAR-γ activation.

CONCLUSION

Our results show that alliin ameliorates DSS-induced ulcerative colitis and inhibits the inflammatory responses in LPS-stimulated RAW264.7 cells partly through inhibiting ERK1/2-, JNK-/PPAR-γ-stimulated NF-κB/AP-1/STAT-1 activations.

Lignan derivatives from Selaginella tamariscina and their nitric oxide inhibitory effects in LPS-stimulated RAW 264.7 cells

The chemical characterization of Selaginella tamariscina leaves resulted in the isolation of five lignanoside derivatives (1-4 and 6) and one neolignan (5). These compounds include three new lignanosides, tamariscinosides D-F (1-3), and one liriodendrin (4) that were isolated for the first time from this plant, together with two known compounds, (2R,3S)-dihydro-2-(3,5-dimethoxy-4-hydroxyphenyl)-7-methoxy-5-acetyl-benzofuran (5) and moellenoside B (6). The chemical structures of these isolated compounds were determined using 1D and 2D NMR, MS, and CD spectroscopic data, and the results were compared to data previously reported in the literatures. These compounds were also evaluated in terms of their inhibition of NO production in lipopolysaccharide (LPS)-stimulated activity in the macrophage cell line RAW 264.7. Among them, compounds 1, 2, 5, and 6 exhibited a significant inhibition with IC₅₀ values ranging from 32.3 to 55.8μM.

Rhododendron album Blume inhibits iNOS and COX-2 expression in LPS-stimulated RAW264.7 cells through the downregulation of NF-κB signaling

Rhododendron album Blume (RA) has traditionally been used as an herbal medicine and is considered to have anti-inflammatory properties. In the present study, we screened RA extracts with anti-inflammatory properties. The biological effects of an RA methanol extract (RAME) on inflammation were investigated in lipopolysaccharide (LPS)-stimulated mouse RAW264.7 cells. We investigated the effects of RAME on the production of nitric oxide (NO) and prostaglandin E2 (PGE2) in LPS-stimulated RAW264.7 cells. To explore the anti-inflammatory mechanisms of RAME, we measured the mRNA and protein expression of pro-inflammatory mediators induced by RAME in the LPS-stimulated RAW264.7 cells by RT-PCR and western blot analysis, respectively. RAME significantly inhibited the production of NO, PGE2, interleukin (IL)-6, IL-1β and tumor necrosis factor (TNF)-α in the LPS-stimulated RAW264.7 cells. It also suppressed the mRNA and protein expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2) and mitogen-activated protein kinases (MAPKs) with a concomitant decrease in the nuclear translocation of nuclear factor-κB (NF-κB) in the LPS-stimulated RAW264.7 cells. These results indicate that RAME inhibits LPS-induced inflammatory responses. These effects were considered to be strongly associated with the suppression of NF-κB activation. We therefore suggest that RAME may be prove to be an effective therapeutic agent for the treatment of inflammatory diseases.

Organic nitrates: past, present and future

Nitric oxide (NO) is one of the most important vasodilator molecules produced by the endothelium. It has already been established that NO/cGMP signaling pathway deficiencies are involved in the pathophysiological mechanisms of many cardiovascular diseases. In this context, the development of NO-releasing drugs for therapeutic use appears to be an effective alternative to replace the deficient endogenous NO and mimic the role of this molecule in the body. Organic nitrates represent the oldest class of NO donors that have been clinically used. Considering that tolerance can occur when these drugs are applied chronically, the search for new compounds of this class with lower tolerance potential is increasing. Here, we briefly discuss the mechanisms involved in nitrate tolerance and highlight some achievements from our group in the development of new organic nitrates and their preclinical application in cardiovascular disorders.

Oxidative stress and nitrosative stress are involved in different stages of proteolytic pulmonary emphysema

Our aim was to investigate the role of oxidative stress in elastase-induced pulmonary emphysema. C57BL/6 mice were subjected to pancreatic porcine elastase (PPE) instillation (0.05 or 0.5 U per mouse, i.t.) to induce pulmonary emphysema. Lungs were collected on days 7, 14, and 21 after PPE instillation. The control group was sham injected. Also, mice treated with 1% aminoguanidine (AMG) and inducible NO synthase (iNOS) knockout mice received 0.5 U PPE (i.t.), and lungs were analyzed 21 days after. We performed bronchoalveolar lavage, biochemical analyses of oxidative stress, and lung stereology and morphometry assays. Emphysema was observed histologically at 21 days after 0.5 U PPE treatment; tissues from these mice exhibited increased alveolar linear intercept and air-space volume density in comparison with the control group. TNF-α was elevated at 7 and 14 days after 0.5 U PPE treatment, concomitant with a reduction in the IL-10 levels at the same time points. Myeloperoxidase was elevated in all groups treated with 0.5 U PPE. Oxidative stress was observed during early stages of emphysema, with increased nitrite levels and malondialdehyde and superoxide dismutase activity at 7 days after 0.5 U PPE treatment. Glutathione peroxidase activity was increased in all groups treated with 0.5 U PPE. The emphysema was attenuated when iNOS was inhibited using 1% AMG and in iNOS knockout mice. Furthermore, proteolytic stimulation by PPE enhanced the expression of nitrotyrosine and iNOS, whereas the PPE+AMG group showed low expression of iNOS and nitrotyrosine. PPE stimulus also induced endothelial (e) NOS expression, whereas AMG reduced eNOS. Our results suggest that the oxidative and nitrosative stress pathways are triggered by nitric oxide production via iNOS expression in pulmonary emphysema.

Effects of phenylethanoid glycosides from Digitalis purpurea L. on the expression of inducible nitric oxide synthase

We have isolated four different phenylethanoid glycosides (purpureaside A, desrhamnosyl acteo-side, calceolarioside B and plantainoside D) from the leaves of Digitalis purpurea (foxglove). The effects of these glycosides on activator protein-1 (AP-1)-mediated inducible nitric oxide synthase (iNOS) gene expression in the Raw264.7 macrophage cell line have been studied. Of these four glycosides, purpureaside A potently inhibited iNOS induction by lipopolysaccharide (LPS). Increase in iNOS mRNA by LPS was completely suppressed by purpureaside A. Purpureaside A did not significantly affect LPS-inducible nuclear factor-kB (NF-kB) activation or the nuclear translocation of p65. Moreover, a reporter gene assay using AP-1 specific luciferase reporter revealed that the enhanced activity of AP-1 by LPS was completely abolished in cells treated with purpureaside A. These results demonstrated that purpureaside A inhibited LPS-inducible iNOS expression in macrophages through the suppression of AP-1, but not of NF-kB.

Transcriptional and post-transcriptional regulation of iNOS expression in human chondrocytes

Chondrocytes are important for the development and maintenance of articular cartilage. However, both in osteoarthritis (OA) and rheumatoid arthritis (RA) chondrocytes are involved in the process of cartilage degradation and synthesize important immunomodulatory mediators, including nitric oxide (NO) generated by the inducible NO synthase (iNOS). To uncover the role of iNOS in the pathomechanisms of OA and RA, we analyzed the regulation of iNOS expression using immortalized human chondrocytes as a reproducible model. In C-28/I2 chondrocytes, iNOS expression was associated with the expression of the chondrocyte phenotype. Peak induction by a cytokine cocktail occurred between 6 and 8h and declined by 24h. Inhibition of p38MAPK, NF-kappaB and the JAK2-STAT-1alpha pathways resulted in a reduction of iNOS expression. In contrast to other cell types, the cytokine-mediated induction of the human iNOS promoter paralleled the induction rate of the iNOS mRNA expression in C-28/I2 chondrocytes. However, in addition post-transcriptional regulation of iNOS expression by the RNA binding protein KSRP seems to operate in these cells. As seen in other chondrocyte models, glucocorticoids were not able to inhibit cytokine-induced iNOS expression in C-28/I2 cells, due to the lack of the glucocorticoid receptor mRNA expression. In this model of glucocorticoid-resistance, the new fungal anti-inflammatory compound S-curvularin was able to inhibit cytokine-induced iNOS expression and iNOS-dependent NO-production. In summary, we demonstrate for the first time that differentiated human immortalized C-28/I2 chondrocytes are a representative cell culture model to investigate iNOS gene expression in human joint diseases.

4-Hydroxykobusin Inhibits the Induction of Nitric Oxide Synthase by Inhibiting NF-.KAPPA.B and AP-1 Activation

We recently isolated a novel lignan, 4-hydroxykobusin from Geranium thunbergii (Liu et al., Arch. Pharm. Res., 29, 1109-1113, 2006). Here, we studied its effect on the expression of inducible nitric oxide synthase (iNOS) gene in RAW264.7 cells. 4-Hydroxykobusin inhibited nitric oxide (NO) production in a concentration-dependent manner and blocked the lipopolysaccharide (LPS)-induced expression of inducible nitric oxide synthase (iNOS). To identify the mechanistic basis for its inhibition of iNOS induction, we examined the effect of 4-hydroxykobusin on the transactivation of iNOS gene by luciferase reporter activity using -1.59 kb flanking region. The lignan suppressed the reporter gene activity and the LPS-induced reporter activations of nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) were also significantly blocked by 4-hydroxykobusin. These findings suggest that the inhibition of LPS-induced NO formation by 4-hydroxykobusin is due to its inhibition of NF-kappaB and AP-1 activation.

Potent inhibition of the inductions of inducible nitric oxide synthase and cyclooxygenase-2 by taiwaniaflavone

The improper productions of nitric oxide and prostaglandins following the inductions of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) are involved in the pathogenesis of chronic inflammation. Selaginella tamariscina is used as an oriental medicine for its anti-inflammatory effects. Here, we isolated taiwaniaflavone from S. tamariscina and investigated whether taiwaniaflavone affects the induction of iNOS and COX-2 in RAW264.7 macrophages stimulated with lipopolysaccharide. We found that taiwaniaflavone blocks the transactivations of iNOS and COX-2 genes by blocking the nuclear translocation of p65 and subsequent nuclear factor-kappaB inactivation. It is known that NF-kappaB activation is controlled by the phosphorylation and subsequent degradation of I-kappaBalpha, and in the present study, we found that the phosphorylation and degradation of I-kappaBalpha were also inhibited by taiwaniaflavone. Our findings indicate that taiwaniaflavone may provide a developmental basis for an agent against inflammatory diseases.

7,7'-Dihydroxy bursehernin inhibits the expression of inducible nitric oxide synthase through NF-kappaB DNA binding suppression

This study isolated a lignan, 7,7'-dihydroxy bursehernin, from Geranium thunbergii and investigated whether or not the lignan affects the induction of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in RAW264.7 macrophages stimulated with lipopolysaccharide (LPS). The gel shift analysis and luciferase reporter gene assays using the iNOS promoter and nuclear factor-kappaB (NF-kappaB) minimal promoter showed that a treatment with 7,7'-dihydroxy bursehernin reduced the reporter activities and binding of NF-kappaB to the NF-kappaB consensus sequence, while it had no effect on the nuclear translocation of p65 and the phosphorylation/degradation of I-kappaBalpha. It was reported that a few natural compounds directly suppressed the binding activity of the NF-kappaB components to DNA. The NF-kappaB binding activity was not reversed by the in vitro exposure of the nuclear extracts to 7,7'-dihydroxy bursehernin, which suggest that a metabolite(s) of 7,7'-dihydroxy bursehernin might target the binding of the NF-kappaB complex to the DNA binding domain region in the promoter region of the iNOS gene. After incubation of RAW264.7 cells with 7,7-dihydroxy bursehernin for 18h, the levels of parent compound were negligible; while a main metabolite, 4-[4-(n-hydroxy-phenyl)-2,3-dimethyl-buta-1,3-dienyl]-benzene-1,2-diol was detected in cell lysates and culture medium.

Inhibition of lipopolysaccharide-inducible nitric oxide synthase expression by acteoside through blocking of AP-1 activation

Acteoside is a phenylpropanoid glycoside with antioxidant and anti-inflammatory activities. We isolated acteoside from Buddlejae Flos, which has been used as a traditional medicine to treat conjunctive congestion and sepsis. The effect of acteoside on the expression of the inducible nitric oxide synthase (iNOS) gene was examined in the Raw264.7 macrophage cell line. An acteoside pretreatment significantly inhibited the release of NO in the cells treated with lipopolysaccharide (LPS). Western blot and RT-PCR analyses revealed that acteoside inhibited the LPS-induced levels of the iNOS protein and mRNA. Activation of the nuclear factor-kappaB (NF-kappaB) and the activator protein-1 (AP-1) is the key step in the signaling pathways mediating iNOS induction. In this study, acteoside selectively suppressed AP-1 activation, which may be essential for iNOS induction in the LPS-treated macrophages. The inhibitory effect of AP-1 activation by acteoside may be associated with the anti-inflammatory effects of Buddlejae Flos.

Renal cortex remodeling in nitric oxide deficient rats treated with enalapril

The kidney NO synthase is one of the most important renal controlling systems. This paper aims the quantification of renal cortical components involved in blood pressure regulation under NOs blockade. Spontaneous hypertensive rats (SHRs) are submitted to chronic blockade of NOs by L-nitro-arginine-methyl-ester (L-NAME) and an ACE inhibitor (enalapril) in comparison with the normotensive Wistar rats. Twenty SHRs and 5 Wistar rats were divided in 5 groups and observed for 21 days for blood pressure (BP) and serum creatinine: control Wistar (5) (C-W), control SHR (5) (C-SHR), L-SHR (5)--received L-NAME 30 mg/kg/day, L+E-SHR (5)--received L-NAME and Enalapril maleate 15 mg/kg/day, E-SHR (5)--received Enalapril maleate. A quantitative morphometric study (glomerular density, QA[gl], interstitium volume density, Vv[i], tubular surface and length densities, Sv[t] and Lv[t]) were performed at the end. The BP reached 226+/-15 mmHg in L-SHR group. The BP difference between the L-SHR and the C-SHR groups was significant from the first week while the E-SHR group became significant from the second week. At the end of the experiment the BP of the E-SHR group was similar to the BP in the C-W group. The QA[gl] was similar among C-SHR, L-SHR and L+E-SHR groups and no difference was found between E-SHR and C-W groups. In the L-SHRs serum creatinine was greatly increased, and microscopy showed thickening of arteriolar tunica media with an increase of the wall-to-lumen ratio, perivascular fibrosis, inflammatory infiltrated, tubular atrophy and interstitial fibrosis with focal segmental glomerulosclerosis. The use of enalapril was not completely efficient in reducing BP and morphological injury when the hypertension of SHRs was increased with the NOs blockade suggesting that NO deficiency-induced hypertension is not entirely mediated by the RAAS.

Inhibitory mechanisms of YC-1 and PMC in the induction of iNOS expression by lipoteichoic acid in RAW 264.7 macrophages

In the present study, the signal pathways involved in NO formation and iNOS expression in RAW 264.7 macrophages stimulated by LTA were investigated. We also compared the relative inhibitory activities and mechanisms of PMC, a novel potent antioxidant of alpha-tocopherol derivatives, with those of YC-1, an sGC activator, on the induction of iNOS expression by LTA in cultured macrophages in vitro and LTA-induced hypotension in vivo. LTA induced concentration (0.1-50 microg/mL)- and time (4-24 hr)-dependent increases in nitrite (an indicator of NO biosynthesis) in macrophages. Both PMC (50 microM) and YC-1 (10 microM) inhibited NO production, iNOS protein, mRNA expression, and IkappaBalpha degradation upon stimulation by LTA (20 microg/mL) in macrophages. On the other hand, PMC (50 microM) almost completely suppressed JNK/SAPK activation, whereas YC-1 (10 microM) only partially inhibited its activation in LTA-stimulated macrophages. Moreover, PMC (10 mg/kg, i.v.) and YC-1 (5 mg/kg, i.v.) significantly inhibited the fall in MAP stimulated by LTA (10 mg/kg, i.v.) in rats. In conclusion, we demonstrate that YC-1 shows more-potent activity than PMC at abrogating the expression of iNOS in macrophages in vitro and reversing delayed hypotension in rats with endotoxic shock stimulated by LTA. The inhibitory mechanisms of PMC may be due to its antioxidative properties, with a resulting influence on JNK/SAPK and NF-kappaB activations. YC-1 may be mediated by increasing cyclic GMP, followed by, at least partly, inhibition of JNK/SAPK and NF-kappaB activations, thereby leading to inhibition of iNOS expression.

Decrease in activity of smooth muscle L-type Ca2+ channels and its reversal by NF-kappaB inhibitors in Crohn's colitis model

We investigated the mechanisms of dysmotility of the colonic circular muscle of the Crohn's disease rat model. Contractions induced by KCl, carbachol, and Bay K 8644 were decreased in circular smooth muscles isolated from 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis rat colon. However, the absolute force and Ca2+ sensitivity of contractile proteins were not affected as assessed in alpha-toxin permeabilized smooth muscle. The current density of the L-type Ca2+ channel in circular smooth muscle cells was significantly decreased in the TNBS-treated colonic cells. However, expressions of the L-type Ca2+ channel mRNA and protein did not differ between control and TNBS-treated preparations. Pretreatment with the NF-kappaB inhibitors pyrrolidinedithiocarbamate and sulfasalazine partially recovered the decreased contractility and current density of the L-type Ca2+ channel by TNBS treatment. These results suggest that the decrease in the contraction of circular smooth muscle isolated from TNBS-induced colitis rat colon, which may be related to gut dysmotility in Crohn's disease, is attributable to the decreased activity of the L-type Ca2+ channel. The dysfunction of the L-type Ca2+ channel may be mediated by NF-kappaB-dependent pathways.

Cyclooxygenase inhibition as a strategy to ameliorate brain injury

Cyclooxygenase (COX) is the obligate, rate-limiting enzyme for the conversion of arachidonic acid into prostaglandins. Two COX enzymes have been identified: a constitutively expressed COX-1 and an inducible, highly regulated COX-2. Widely used to treat chronic inflammatory disorders, COX inhibitors have shown promise in attenuating inflammation associated with brain injury. However, the use of COX inhibition in the treatment of brain injury has met with mixed success. This review summarizes our current understanding of COX expression in the central nervous system and the effects of COX inhibitors on brain injury. Three major targets for COX inhibition in the treatment brain injury have been identified. These are the cerebrovasculature, COX-2 expression by vulnerable neurons, and the neuroinflammatory response. Evidence suggests that given the right treatment paradigm, COX inhibition can influence each of these three targets. Drug interactions and general considerations for administrative paradigms are also discussed. Although therapies targeted to specific prostaglandin species, such as PGE2, might prove more ameliorative for brain injury, at the present time non-specific COX inhibitors and COX-2 specific inhibitors are readily available to researchers and clinicians. We believe that COX inhibition will be a useful, ameliorative adjunct in the treatment of most forms of brain injury.

Novel agents in the therapy of endotoxic shock

Endotoxic shock, or Gram-negative septic shock, can occur as a component of Gram-negative sepsis and is characterised by hypotension, poor tissue perfusion and multi-organ dysfunction. Despite antibiotic therapy and intensive care management, the morbidity and mortality rates of Gram-negative septic shock remain high. Endotoxin mediates its effects through interaction with receptors on the surface of a variety of host cells. These interactions result in the production and release of numerous biochemical mediators including nitric oxide, cytokines, prostaglandins and leukotrienes and toxic oxygen radicals. It is these biochemical mediators that exert toxic effects during endotoxic shock and which are often the target of novel treatment strategies. Several of these pharmacological agents are currently being investigated for use in Gram-negative septic shock and include inhibitors of the enzyme responsible for nitric oxide production, scavengers of the nitric oxide molecule and cytokine modulators. Although many agents have been studied for potential use as modulators of cytokine levels, this study will focus on pentoxifylline and the 21-aminosteroids, or lazaroids. Examination of the literature regarding pharmacological agents used to treat endotoxic shock often yields confusing and contradictory results. The reasons for these mixed results include differences in models, drug dosages, dosing methods and intervals and timing of administration relative to disease duration and severity. However, despite mixed results, several of the drugs discussed in this paper offer promise in the therapy of an often frustrating and lethal condition.

Nitric oxide based influence of nitrates on micturition in patients with benign prostatic hyperplasia

BACKGROUND

Nitric oxide (NO) is involved in the physiologic regulation of smooth muscle relaxation in the prostate. Organic nitrates act as NO donors. In this prospective open study we prove the influence of orally given nitrates on micturition.

METHODS

Thirty-two patients underwent a urological medical check-up prior to starting nitrate medication for cardiovascular disease. We examined peak flow rates, residual urine, IPS-score, PSA level and prostate volume. Exact inclusion and exclusion criteria were defined. Fifteen patients suffered from obstructive symptoms, 17 patients reported no subjective micturition problems. Urological re-evaluation was performed two weeks and three months after nitrate medication.

RESULTS

A significant improvement of peak urinary flow rates (+3.1 ml/s; p<0.05), IPS score and significant decrease of residual urine volume (-22 ml; p<0.05) were found in the symptomatic patients. No significant changes of micturition parameters were found in asymptomatic patients. PSA levels and prostate volumes did not change in either groups.

CONCLUSIONS

Organic nitrates influence micturition parameters in patients with obstructive benign prostatic hyperplasia. This might be explained by the known mechanism of NO donation (smooth muscle relaxation) of nitrates. More functional controlled studies are necessary to describe the grade of influence of nitrates on the prostate. Concomitant oral medication with nitrates must be considered as a relevant bias factor on BPH in future clinical studies.

Treatment of endotoxic shock: glucocorticoids, lazaroids, nonsteroidals, others

Review of the literature would indicate that a therapy inhibiting a single step in the inflammatory mediator cascade, although potentially beneficial, cannot serve as the "magic bullet" in endotoxic shock. Thus, combination therapy using drugs that target multiple steps in the mediator cascade may prove useful in the future. Until controlled clinical studies have been performed in veterinary medicine using the agents discussed in this manuscript (or others), many questions will remain regarding the best possible pharmacologic therapies to use in supplementing traditional supportive care (e.g., fluids, broad-spectrum antimicrobials) measures. Many of the therapies discussed in this manuscript hold tremendous potential, but must be administered before endotoxic shock occurs or early in the course of endotoxic shock to elicit a beneficial response. Unfortunately this is not usually possible in the clinical situation. Further, the possibility of eliciting a detrimental response by use of drugs at inappropriate dosages or too late in the course of the disease must be considered. In time, therapies may be grouped into those that hold promise for being beneficial in the patient at risk for endotoxic shock and those that are beneficial for treatment of established endotoxic shock. Therapies that may hold promise for the patient with established endotoxic shock possibly include the lazaroids, certain NSAIDs, pentoxifylline, and selective inhibitors of iNOS activity. Although still controversial, methylprednisolone and other glucocorticoids are probably best reserved for the patient at risk for endotoxic shock, or those identified very early in the course of endotoxemia and endotoxic shock, and should never be used in conjunction with NSAIDs. Since no one therapy is likely to provide the "magic bullet" for the patient in endotoxic shock, treatment may ultimately involve combination therapy using some of these drugs that target different pathways and mediators and may also include antibodies against endotoxin or its mediators.

Evaluation of nitric oxide production by Leishmania infantum-infected dog macrophages

Protozoa of the genus Leishmania (L.) infect reticuloendothelial cells of several mammalian species, including dogs, in which they often give rise to a chronic, not self-healing visceral disease. Since the parasitocidal mechanism of macrophages towards Leishmania in dog has not yet been well investigated, in this work we have evaluated in Leishmania infantum-infected macrophage cultures from 10 healthy dogs, killing capacity and nitric oxide (NO) production, in terms of nitrite (NO2) levels. Parallel experiments were performed on macrophages stimulated with both Concanavalin A (ConA)-activated PBMC supernatants and Salmonella typhimurium lipopolysaccharide (LPS), and in the same conditions, but in the presence of the NO synthase inhibitor L-N monomethylarginine (L-NMMA). In L. infantum-infected macrophages, nitric oxide production was observed at a concentration significantly higher after stimulation with both Con A-activated PBMC supernatants and LPS than that observed in uninfected cells cultured in medium alone, or infected cells unstimulated or stimulated by PBMC supernatants or LPS alone, respectively. Moreover, NO production was abolished in the presence of the NO synthase inhibitor L-NMMA. Finally, killing of Leishmania by macrophages was significantly reduced in the presence of L-NMMA.

Water soluble furoxan derivatives as NO prodrugs

The synthesis, characterization, NO donor properties, and in vitro vasodilating activity of a series of water soluble furoxans (5-14a,b) are described. All of the compounds released NO when treated with a large excess of cysteine under physiological conditions (pH 7.4; 37 degrees C). The amount of NO produced after 1 h of incubation was evaluated by detecting nitrites, via the Griess reaction. Derivatives 5b, 7b, and 14b were able to release nitric oxide also in the absence of the thiol cofactor. The initial rates of NO release were determined at different concentrations, using a spectrophotometric technique based on the NO-induced oxidation of oxyhemoglobin (HbO2) to methemoglobin (MetHb). The initial rates of NO release were linearly dependent on the concentrations of the single compounds. The vasodilating potency (EC50) of all the derivatives was assessed on rat aortic strips precontracted with noradrenaline. Correlation between potency and initial NO release rate is discussed.

Nitric oxide synthase is expressed in experimental malignant glioma and influences tumour blood flow

The distribution and function of nitric oxide synthase (NOS) was studied in the rodent C6 implantation glioma model. Using a histochemical stain for NADPH diaphorase, which colocalises with NOS, morphological studies revealed non homogenous staining of the constituent tumour cells and the neoplastic endothelium. Immunocytochemical staining for macrophages (ED1, ED2) showed dense positivity at the tumour brain interface with more patchy positivity within the tumour mass. This finding suggests that both macrophages, which are known to produce large amounts of NO, and the C6 cells contribute to the NADPH diaphorase positivity. Administration of the NOS inhibitor Ng-nitro-L-argine methyl ester (L-NAME) significantly reduced both tumour (40%) and contralateral local cerebral blood flow (20%) compared to control animals. These findings demonstrate that (i) NOS is present in experimental malignant glioma; (ii) NO mediated mechanisms contribute to tumour blood vessel dilatation and blood flow regulation; and (iii) using this model there is a significant differential sensitivity of the tumour and brain parenchymal vascular beds to a NOS inhibitor. Further investigations are required to determine the potential therapeutic and biological relevance of these findings and the relative contributions of tumour cells, neoplastic endothelium and reactive macrophages to NO mechanism in gliomas.