Rapid induction of messenger RNA for nitric oxide synthase II in rat neutrophils in vivo by endotoxin and its suppression by prednisolone

Effect of Dexamethasone Combination with Gentamicin in Chemical Labyrinthectomy on Hearing Preservation and Vertigo Control in Patients with Unilateral Meniere's Disease: A Randomized Controlled Clinical Trial

Chemical labyrinthectomy using gentamicin is a popular method for treating intractable vertigo attacks in Meniere’s disease. However, the risk of hearing loss remains a major concern for clinicians. We investigated the effect of simultaneous dexamethasone and gentamicin application on hearing preservation and vertigo control in patients with intractable unilateral Meniere’s disease. A single-institutional, prospective, single-blinded, randomized clinical trial was conducted. Gentamicin-soaked Gelfoam^® was directly applied on the oval window following middle ear exploration. On the round window, dexamethasone-soaked Gelfoam^® was applied in the gentamicin with dexamethasone group (GD group, n = 18), and saline-soaked Gelfoam^® was applied in the gentamicin with sham reagent group (GO group, n = 19). The hearing change 8 weeks after the procedure and vertigo control 2–12 months after the procedure were investigated. The high-frequency hearing threshold was significantly increased in the GO group (p = 0.005 and 0.012 for 4 and 8 kHz, respectively), but not in the GD group. The short-term (2–6 months) vertigo control was more successful in the GD group (57.89% vs. 94.44%, p = 0.019), but long-term control (6–12 months) was insignificant. In conclusion, the combined application of gentamicin and dexamethasone in chemical labyrinthectomy is an effective method for protecting high-frequency hearing and vertigo control.

Anti-apoptotic effect of dexamethasone in an ototoxicity model

Background

Dexamethasone (DEX) is used for the treatment of various inner ear diseases. However, the molecular mechanism of DEX on gentamicin induced hair cell damage is not known. Therefore, this study investigated the protective effect of DEX on gentamicin (GM)-induced ototoxicity and the effect of GM on the expression of apoptosis related genes.

Methods

The protective effects of DEX were measured by phalloidin staining of explant cultures of organ of Corti from postnatal day 2–3 mice with GM-induced hair cell loss. Terminal deoxynucleotidyl transferase dUTP nick end labeling staining was used to detect apoptosis and immunofluorescence was done to analyze the effect of DEX on the expression of apoptosis related genes.

Results

Cochlear explant cultures of postnatal day-4-old mice were exposed to 0, 1, 5, 10, 30, 50, and 100 μg/ml DEX and GM during culture. DEX protected from GM-induced hair cell loss in the inner ear of postnatal day 4 mice. To understand the molecular mechanisms by which DEX pre-treatment decreased hair cell loss, the testes of cochlear explant cultures of postnatal day 4 mice were examined for changes in expression of cochlear apoptosis mediators. The pro-apoptotic protein Bax was significantly down-regulated and numbers of apoptotic hair cells were decreased.

Conclusions

DEX has a protective effect on GM-induced hair cell loss in neonatal cochlea cultures and the protective mechanism may involve inhibition of the mitochondrial apoptosis pathway. The combination with scaffold technique can improve delivery of DEX into the inner ear to protect GM-induced ototoxicity.

Nitric oxide synthesis by hepatic cells is down regulated in endotoxin tolerant rats

The administration of a non-lethal dose of lipopolysaccharide (LPS) to experimental animals and human subjects results in a state of hyporesponsiveness to a second lethal challenge. Relatively little is known about the mechanisms of this endotoxin tolerance, especially about the induction of nitric oxide formation after LPS under these condition. Male Sprague-Dawley rats were divided into four groups: 1) rats that received a non-lethal i.v. injection of Escherichia coli LPS (0.5 mg/kg i.v., 'low dose'); 2) rats given a single injection of 'high dose' of LPS (3 mg/kg i.v.); 3) rats administered a low dose of LPS 12-168 h before they were challenged by a second injection of a high dose LPS (0.5 mg/kg followed by 3 mg/kg i.v., 'double injection'); and 4) rats treated with saline instead of LPS (1 ml/kg i.v., 'control'). 6 h after the high dose LPS, the livers were perfused with Krebs Henseleit buffer in a recirculating system at 37°C for 1 h, or hepatic cells were isolated. The isolated hepatocytes, Kupffer and hepatic endothelial cells were incubated in Hank's balanced salt solution (HBSS), containing 1 mM L-arginine, at 37°C for 3 h. The liver perfusate and supernatant from cell incubation were collected for determination of nitrite plus nitrate. Transcripts for inducible nitric oxide synthase (iNOS) were measured by cDNA equalized reverse transcription polymerase chain reaction in freshly isolated hepatic cells. Plasma glucose, lactate, alanine aminotransferase (ALT) and reactive nitrogen intermediates (RNIs) were also determined. High dose LPS alone caused a significant hypoglycemia (from 121.6 ± 3.0 to 84.5 ± 9.2 mg/dl), lactacidemia (from 8.3 ± 0.7 to 40.2 ± 5.7 mg/dl) and increase in plasma ALT (from 20.5 ± 2.8 to 477.8 ± 105.4 u/l). RNI levels in plasma also increased after 3 h and reached the maximum at 24 h after LPS (from 32.0 ± 1.3 to 795.3 ± 121.5 μM). RNI release from the perfused liver 6 h after high dose LPS was increased from 9.0 ± 2.0 to 156.6 ± 24.6 nmoles/g.h. Freshly isolated hepatic cells from control or low dose LPS treated rats released only small amounts of RNI. After high dose LPS administration, however, RNI release by hepatocytes, Kupffer and hepatic endothelial cells was increased 2.5, 14 and 4.5 fold, respectively. The 'high dose' LPS-induced increase of RNI production was associated with upregulation of iNOS mRNA in Kupffer and endothelial cells. After double injection of LPS (group 3), a protective effect was demonstrated by attenuated mortality, glucose changes, lactacidemia, and amino transferase activity, as compared to the high dose group. LPS tolerance with regard to RNI production by the liver was observed by 12 h, reached its maximum at about 72 h and was still evident even 120 h after the first injection of LPS. An attenuated RNI production in the supernatant from isolated hepatic cell cultures was also observed in the double injection group as compared to RNI release following the 'high dose' alone. This was associated with suppression of upregulation of iNOS mRNA induced by high dose LPS in Kupffer and hepatic endothelial cells. In contrast to the attenuated hepatic release of RNI during acute tolerance, RNI levels in plasma did not show hyporesponsiveness.

Comparison of the protective effects of intratympanic dexamethasone and methylprednisolone against cisplatin-induced ototoxicity

OBJECTIVE

This study aimed to compare the efficacies of intratympanic dexamethasone and methylprednisolone in preventing in cisplatin-induced ototoxicity in rats.

METHODS

Experimental groups of rats (n = 8 each) received intratympanic isotonic saline, intraperitoneal cisplatin and intratympanic isotonic saline, intraperitoneal cisplatin and intratympanic dexamethasone, or intraperitoneal cisplatin and intratympanic methylprednisolone. Distortion product otoacoustic emission thresholds were compared on days 0 and 10 in all rats, and correlations between drug effects and changes in cochlear histology were evaluated.

RESULTS

Distortion product otoacoustic emission thresholds were comparable in groups III and IV (p > 0.05). Significant protection against cisplatin-induced ototoxicity was seen in groups III and IV compared with group II (p < 0.05). Dexamethasone and, to a lesser extent, methylprednisolone protected against cellular apoptosis in cisplatin-induced ototoxicity.

CONCLUSION

Dexamethasone (and possibly methylprednisolone) may be clinically useful as an intratympanic chemopreventive agent to treat cisplatin ototoxicity. Future clinical studies should investigate the use of dexamethasone for this purpose in adult patients.

Gaseous therapeutics in acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) remain major causes of morbidity and mortality in critical care medicine despite advances in therapeutic modalities. ALI can be associated with sepsis, trauma, pharmaceutical or xenobiotic exposures, high oxygen therapy (hyperoxia), and mechanical ventilation. Of the small gas molecules (NO, CO, H₂S) that arise in human beings from endogenous enzymatic activities, the physiological significance of NO is well established, whereas that of CO or H₂S remains controversial. Recent studies have explored the potential efficacy of inhalation therapies using these small gas molecules in animal models of ALI. NO has vasoregulatory and redox-active properties and can function as a selective pulmonary vasodilator. Inhaled NO (iNO) has shown promise as a therapy in animal models of ALI including endotoxin challenge, ischemia/reperfusion (I/R) injury, and lung transplantation. CO, another diatomic gas, can exert cellular tissue protection through antiapoptotic, anti-inflammatory, and antiproliferative effects. CO has shown therapeutic potential in animal models of endotoxin challenge, oxidative lung injury, I/R injury, pulmonary fibrosis, ventilator-induced lung injury, and lung transplantation. H₂S, a third potential therapeutic gas, can induce hypometabolic states in mice and can confer both pro- and anti-inflammatory effects in rodent models of ALI and sepsis. Clinical studies have shown variable results for the efficacy of iNO in lung transplantation and failure for this therapy to improve mortality in ARDS patients. No clinical studies have been conducted with H₂S. The clinical efficacy of CO remains unclear and awaits further controlled clinical studies in transplantation and sepsis.

Development of oxidative stress and cell damage in the liver of rats with water-immersion restraint stress

We examined how oxidative stress and cell damage develop in the liver of rats subjected to water-immersion stress (WIRS). In rats subjected to WIRS for 1.5, 3 or 6 h, serum alanine aminotransferase and aspartate aminotransferase activities increased time-dependently. In the liver tissue, vacuolization and apoptosis occurred at 1.5 h of WIRS and vacuolization further developed without further appearance of apoptosis at 3 h or 6 h. Serum lipid peroxide (LPO) and NOx (nitrite/nitrate) concentrations increased at 3 h of WIRS and these increases were enhanced at 6 h. In liver tissue, increases in LPO and NOx concentrations and myeloperoxidase activity and decreases in ascorbic acid and reduced glutathione concentrations and superoxide dismutase activity occurred at 3 h of WIRS and these changes were enhanced at 6 h, although vitamin E concentration and xanthine oxidase activity were unchanged. These results indicate that oxidative stress in the liver of rats with WIRS develops after the appearance of cell damage in the tissue, and suggests that oxidative stress is caused through disruption of the antioxidant defense system and increases in NO generation and neutrophil infiltration in the liver, which may contribute to the progression of cell damage in the tissue.

Intratympanic Dexamethasone to Prevent Cisplatin Ototoxicity

Objective. To determine whether intratympanic administration of dexamethasone reduces ototoxicity from systemic cisplatin.

Study Design. Prospective animal study.

Setting. Cisplatin chemotherapy induces ototoxicity manifesting as irreversible, sensorineural hearing loss. This is due to damage to the inner ear structures by free radicals. Steroidal anti-inflammatories have been shown to reduce the formation of free radicals and protect hearing in animal models.

Subjects and Methods. Pure tone auditory brainstem responses were obtained in 58 female albino guinea pigs before and 3 days after intraperitoneal (IP) cisplatin chemotherapy. Auditory brainstem responses were also taken up to 1 month after a low dose of cisplatin. Part I consisted of a dosing study to determine the optimal ototoxic dose of cisplatin. In part II, auditory brainstem response thresholds were compared after bilateral intratympanic dexamethasone doses to act as controls. For part III, the otoprotection of dexamethasone against cisplatin was tested in separate bilateral and unilateral studies.

Results. IP injection of 12 mg/kg of cisplatin induced significant hearing loss (57.2 ± 4.4 dB, P < .01) with 0% mortality. Ears treated with intratympanic dexamethasone alone showed no significant threshold changes. Ears that received IP cisplatin and intratympanic dexamethasone showed reduced threshold shifts at 8 kHz when the greatest concentration of dexamethasone was administered.

Conclusion. Modest intratympanic dexamethasone otoprotection of the guinea pig ear was greatest at the highest concentration tested and occurred in a frequency-dependent manner. Intratympanic dexamethasone presents as a safe, simple, and effective treatment modality to minimize cisplatin ototoxicity without interfering with the chemotherapeutic effects of cisplatin.

PDT-induced inflammatory and host responses

Photodynamic therapy (PDT) is used in the management of neoplastic and nonmalignant diseases. Its unique mechanisms of action include direct cytotoxic effects exerted towards tumor cells, destruction of tumor and peritumoral vasculature and induction of local acute inflammatory reaction. The latter develops in response to (1) damage to tumor and stromal cells that leads to the release of cell death-associated molecular patterns (CDAMs) or damage associated molecular patterns (DAMPs), (2) early vascular changes that include increased vascular permeability, vascular occlusion, and release of vasoactive and proinflammatory mediators, (3) activation of alternative pathway of complement leading to generation of potent chemotactic factors, and (4) induction of signaling cascades and transcription factors that trigger secretion of cytokines, matrix metalloproteinases, or adhesion molecules. The majority of studies indicate that induction of local inflammatory response contributes to the antitumor effects of PDT and facilitates development of systemic immunity. However, the degree of PDT-induced inflammation and its subsequent contribution to its antitumor efficacy depend on multiple parameters, such as chemical nature, concentration and subcellular localization of the photosensitizers, the spectral characteristics of the light source, light fluence and fluence rate, oxygenation level, and tumor type. Identification of detailed molecular mechanisms and development of therapeutic approaches modulating PDT-induced inflammation will be necessary to tailor this treatment to particular clinical conditions.

Evolution of portal-systemic collateral vasopressin response in endotoxemic portal hypertensive rats

Cirrhotic patients with portal hypertension and variceal hemorrhage are vulnerable to endotoxemia. However, the direct influence of endotoxemia on portal-systemic collateral vasculature remains unexplored. In this study, portal hypertension was induced in Sprague-Dawley rats by partial portal vein ligation. On the 7th day after portal vein ligation, at 0.5, 1.5, and 5 h post endotoxin (LPS; Escherichia coli serotype O111:B4, 3 mg/kg, i.p., E0.5, E1.5 and E5, respectively) or saline (control, C0.5, C1.5, and C5, respectively) injection, hemodynamic measurements and concentration-response relationships to arginine vasopressin (AVP; 10(-10)-10(-7) mol/L) in collateral vascular bed were obtained. In another six parallel groups, reverse-transcriptase-polymerase chain reaction of iNOS, eNOS, and endothelin 1 (ET-1) mRNA expressions for splenorenal shunt, the most prominent intra-abdominal collateral vessel, was performed. The results showed that E0.5 had lower perfusion pressure changes to AVP and higher splenorenal shunt eNOS expression than C0.5 group (P < 0.05). Compared with C1.5, tachycardia, higher perfusion pressure changes and enhanced splenorenal shunt iNOS and ET-1 expression were observed in E1.5 group (P < 0.05). In E5, systemic and portal hypotension with markedly enhanced collateral AVP responsiveness and splenorenal shunt iNOS and ET-1 expressions were noted (P < 0.05). In conclusion, vasoactive substances counterregulation participates, at least in part, the time-dependent changes of collateral AVP responsiveness in endotoxemic portal hypertensive rats.

Protective effect of L-ascorbic acid against oxidative damage in the liver of rats with water-immersion restraint stress

We examined whether L-ascorbic acid (AA) (or reduced ascorbic acid) protects against oxidative damage in the liver of rats subjected to water-immersion stress (WIRS). AA (100, 250 or 500 mg/kg) was orally administered at 0.5 h before the onset of WIRS. Rats with 6 h of WIRS had increased serum corticosterone, glucose, total ascorbic acid (T-AA), AA, lipid peroxide (LPO), and NOx concentrations and alanine aminotransferase and aspartate aminotrasferase activities. The stressed rats had increased hepatic LPO, NOx, and dehydroascorbic acid concentrations and myeloperoxidase activity, decreased hepatic T-AA, AA, reduced glutathione concentrations and superoxide dismutase activity, and unchanged hepatic vitamin E concentration. Pre-administered AA attenuated the stress-induced changes in serum LPO and NOx concentrations and alanine aminotransferase and aspartate aminotrasferase activities and hepatic LPO, NOx, and T-AA, AA, dehydroascorbic acid, and reduced glutathione concentrations and myeloperoxidase and superoxide dismutase activities dose-dependently. Pre-administered AA did not affect the stress-induced changes in serum corticosterone and glucose concentrations. These results indicate that pre-administered AA protects against oxidative damage in the liver of rats with WIRS possibly by attenuating disruption of the antioxidant defense system and increases in NO generation and neutrophil infiltration in the tissue.

Cisplatin-induced ototoxicity: effect of intratympanic dexamethasone injections

HYPOTHESIS

Intratympanic (IT) application of dexamethasone will reduce ototoxicity associated with systemic cisplatin therapy.

BACKGROUND

Cisplatin is a common chemotherapeutic drug often dose-limited by ototoxicity attributed to the formation of reactive oxygen and nitrogen species damaging critical inner ear structures. Steroids have been shown to reduce formation of reactive oxygen species and thus may reduce ototoxicity. In the present pilot study, we test this hypothesis by IT administration of dexamethasone in a novel murine model of cisplatin ototoxicity.

METHODS

Click- and pure-tone-evoked auditory brainstem responses (ABRs) in young CBA/J mice were measured. The first phase consisted of a dosing study to identify the optimal cisplatin dose for ototoxicity. In the next phase, ABR thresholds were measured in cisplatin-treated mice after 5 days of IT injection of 24 mg/ml of dexamethasone in 1 ear and normal saline in the opposite ear to serve as controls.

RESULTS

Intraperitoneal injection of 14 mg/kg of cisplatin induces significant hearing loss (click-evoked ABR threshold elevation = 12 +/- 7 dB, mu +/- standard error of the mean) with acceptable mortality (20%). The ears that received IT dexamethasone in cisplatin-treated mice had minimal ABR threshold shifts with the click, 8 and 16 kHz of stimuli. There was no significant difference between IT dexamethasone and IT saline ears at 32 kHz.

CONCLUSION

IT dexamethasone protected the mouse ear against cisplatin-induced ototoxicity in a frequency-dependent manner. The present results suggest that IT dexamethasone may be a safe, simple, and effective intervention that minimizes cisplatin ototoxicity without interfering with the chemotherapeutic actions of cisplatin.

Systemic NO production during (septic) shock depends on parenchymal and not on hematopoietic cells: in vivo iNOS expression pattern in (septic) shock

Septic shock is the leading cause of death in noncoronary intensive care units and the 10th leading cause of death overall. Several lines of evidence support an important role for the vasodilator NO in hypotension, a hallmark of septic shock. However, NO may also positively or negatively regulate inflammation, apoptosis, and oxidative stress. These dual effects of NO may relate to its isoform specific production but also to differences in cellular and/or temporal expression. Via bone marrow transplantations, we examined the contribution of hematopoietic cells to the dramatically elevated NO levels seen in (septic) shock. Surprisingly, hematopoietic cells are not responsible at all for the production of circulating NO after systemic tumor necrosis factor or lipopolysaccharide challenge and contribute only marginally in a bacteremic (Salmonella) model of septic shock. Immunohistochemistry identified the nonhematopoietic sources of NO as hepatocytes, paneth cells, and intestinal and renal epithelial cells. In contrast, during granulomatous Bacillus Calmette-Guérin inflammation, the hematopoietic cell population represents the sole source of systemic NO. These mouse data demonstrate that, in contrast to the general conjecture, the dramatically elevated levels of NO during (septic) shock are not produced by hematopoietic cells such as monocytes/macrophages but rather by parenchymal cells in liver, kidney and gut.

Therapeutic efficacy of intra-cochlear administration of methylprednisolone after acoustic trauma caused by gunshot noise in guinea pigs

The therapeutic efficacy of cochlear infusion of methylprednisolone (MP) after an impulse noise trauma (170dB SPL peak) was evaluated in guinea pigs. The compound action potential threshold shifts were measured over a 14 days recovery period after the gunshot exposure. For each animal, one of the cochlea was perfused directly into the scala tympani with MP during 7 days via a mini-osmotic pump, whereas the other cochlea was not pump-implanted. The functional study of hearing was supplemented by histological analysis. Forty eight hours after the trauma, significant differences between auditory threshold shifts in the implanted and non-implanted ears were observed for frequencies above 8kHz. At day 7, the difference was significant for only one frequency and no difference was observed after 14 days recovery. Cochleograms showed that the hair cell losses were significantly lower in the MP treated ears. This work indicates that direct infusion of MP into perilymphatic space accelerates hearing recovery, reduces hair cell losses after impulse noise trauma but does not limit permanent threshold shifts.

ATTENUATION OF ENDOTOXIN-INDUCED OXIDATIVE STRESS AND MULTIPLE ORGAN INJURY BY 3,4-METHYLENEDIOXYPHENOL IN RATS

Endotoxin is a potent inducer of lipid peroxidation (LPO), which is associated with the development of endotoxemia. 3,4-Methylenedioxyphenol (sesamol) is one of the sesame oil lignans with a high anti-LPO effect. Whether sesamol can attenuate endotoxin-induced LPO and multiple organ injury is unknown. After a dose response for sesamol in endotoxin-challenged rats was established, experiments were conducted to assess its effects on hydroxyl radical, peroxynitrite, and superoxide anion counts, activities of superoxide dismutase, catalase, and glutathione peroxidase, as well as the production of nitric oxide (NO) and the expression of inducible NO synthase. In addition, the effects of sesamol on endotoxin-induced hepatic and renal injuries were assessed. Sesamol (a) dose dependently reduced serum LPO inendotoxin-challenged rats, (b) decreased hydroxyl radical and peroxynitrite, but not superoxide anion counts, (c)increased the activities of superoxide dismutase, catalase, and glutathione peroxidase in endotoxin-treated rats, (d)reduced NO production and inducible NO synthase expression, and (e) attenuated hepatic and renal injuries induced by endotoxin in rats. We concluded that sesamol might protect against organ injury by decreasing NO-associated LPO in endotoxemic rats.

The effects of nitric oxide in acute lung injury

Acute lung injury (ALI) is a common clinical problem associated with significant morbidity and mortality. Ongoing clinical and basic research and a greater understanding of the pathophysiology of ALI have not been translated into new anti-inflammatory therapeutic options for patients with ALI, or into a significant improvement in the outcome of ALI. In both animal models and humans with ALI, there is increased endogenous production of nitric oxide (NO) due to enhanced expression and activity of inducible NO synthase (iNOS). This increased presence of iNOS and NO in ALI contributes importantly to the pathophysiology of ALI. However, inhibition of total NO production or selective inhibition of iNOS has not been effective in the treatment of ALI. We have recently suggested that there may be differential effects of NO derived from different cell populations in ALI. This concept of cell-source-specific effects of NO in ALI has potential therapeutic relevance, as targeted iNOS inhibition specifically to key individual cells may be an effective therapeutic approach in patients with ALI. In this paper, we will explore the potential role for endogenous iNOS-derived NO in ALI. We will review the evidence for increased iNOS expression and NO production, the effects of non-selective NOS inhibition, the effects of selective inhibition or deficiency of iNOS, and this concept of cell-source-specific effects of iNOS in both animal models and human ALI.

Nitric oxide synthase is downregulated, while haem oxygenase is increased, in patients with septic shock

BACKGROUND

The vasodilatation characteristic of human septic shock is conventionally attributed to increased nitric oxide production, primarily by extrapolation of animal and human in vitro studies. There are no conclusive studies of human disease, and the cellular source of nitric oxide in human sepsis is not known. Haem oxygenase is upregulated by oxidative stress, but little is known about haem oxygenase expression in human sepsis. Haem oxygenase may modulate nitric oxide production, and may also have a direct effect on vascular tone.

METHODS

Mesenteric arterial smooth muscle (ASM) (obtained during laparotomy) and peripheral blood mononuclear cells (PBMCs) were obtained from patients with early septic shock and from control patients. mRNA levels were determined by real-time RT-PCR.

RESULTS

mRNA for inducible and endothelial nitric oxide synthase was reduced in both ASM and PBMCs from septic patients. In contrast, inducible haem oxygenase mRNA was increased in sepsis in both cell types.

CONCLUSIONS

These results suggest that, rather than being induced, the enzymes which produce nitric oxide are reduced at this time point in human septic shock. Thus many of the in vitro models of sepsis studied to date may not fully replicate human disease. The increase in haem oxygenase expression confirms that these cells have been subjected to oxidative stress in sepsis. The activity of induced haem oxygenase may limit nitric oxide production, while possibly causing vasodilation through production of carbon monoxide.

Direct inner ear infusion of dexamethasone attenuates noise-induced trauma in guinea pig

The protective effect of dexamethasone (DEX) against noise-induced trauma, as reflected in hair cell destruction and elevation in auditory brainstem response (ABR) sensitivity, was assessed in guinea pigs. The animals were administered DEX (1, 10, 100, and 1000 ng/ml) or artificial perilymph (AP) via a mini-osmotic pump directly into scala tympani and, on the fourth day after pump implantation, exposed to 120 dB SPL octave band noise, centered at 4 kHz, for 24 h. Animals receiving DEX demonstrated a dose-dependent reduction in noise-induced outer hair cell loss (significant at 1, 10 and 100 ng/ml DEX animals compared to AP control animals) and a similar attenuation of the noise-induced ABR threshold shifts, observed 7 days following exposure (significant at 100 ng/ml DEX animals compared to AP control animals). These physiological and morphological results indicate that direct infusion of DEX into the perilymphatic space has protective effects against noise-induced trauma in the guinea pig cochlea.

Protective effect of corticosteroid against the cytotoxicity of aminoglycoside otic drops on isolated cochlear outer hair cells

OBJECTIVES

Otic drops are commonly used not only for otitis externa but also for otorrhea in the presence of tympanic membrane perforation or tympanostomy tube. Many studies demonstrated the ototoxicity of aminoglycoside. In our previous study, we observed that gentamicin (GM), when activated with liver extract, demonstrated significant cytotoxicity. The purpose of this study was to assess the protective effect of corticosteroid against the cytotoxicity of GM and tobramycin drops using isolated cochlear outer hair cells (OHCs) in vitro with liver extract.

METHODS

OHCs from adult chinchilla cochleae were exposed to standard bathing solution, liver extract alone, and aminoglycoside otic drops with and without corticosteroid and liver extract. All experiments were performed at an osmolality of 305 +/- 5 mOsm, at room temperature, and for up to 60 minutes. The images of OHCs were recorded using an inverted microscope and analyzed on the Image Pro-Plus 3.0 program. Time to cell death and change of cell length were measured and analyzed.

RESULTS

The time to cell death and percent change in cell length observed was significantly longer in the GM + liver extract + dexamethasone group than the GM + liver extract group (P <.05). The Tobradex + liver extract group showed an insignificant increase in percent change of cell length (P >.05) and significantly increased time to cell death than the tobramycin + liver extract group (P <.05).

CONCLUSION

This study demonstrated that dexamethasone significantly reduced aminoglycoside cytotoxicity.

Use of aminoguanidine (Pimagedine) to prevent the formation of advanced glycation endproducts

Aminoguanidine (AG) is a prototype therapeutic agent for the prevention of formation of advanced glycation endproducts. It reacts rapidly with alpha,beta-dicarbonyl compounds such as methylglyoxal, glyoxal, and 3-deoxyglucosone to prevent the formation of advanced glycation endproducts (AGEs). The adducts formed are substituted 3-amino-1,2,4-triazine derivatives. Inhibition of disease mechanisms, particularly vascular complications in experimental diabetes, by AG has provided evidence that accumulation of AGEs is a risk factor for disease progression. AG has other pharmacological activities, inhibition of nitric oxide synthase and semicarbazide-sensitive amine oxidase (SSAO), at pharmacological concentrations achieved in vivo for which controls are required in anti-glycation studies. AG is a highly reactive nucleophilic reagent that reacts with many biological molecules (pyridoxal phosphate, pyruvate, glucose, malondialdehyde, and others). Use of high concentrations of AG in vitro brings these reactions and related effects into play. It is unadvisable to use concentrations of AG in excess of 500 microM if selective prevention of AGE formation is desired. The peak plasma concentration of AG in clinical therapy was ca. 50 microM. Clinical trial of AG to prevent progression of diabetic nephropathy was terminated early due to safety concerns and apparent lack of efficacy. Pharmacological scavenging of alpha-oxoaldehydes or stimulation of host alpha-oxoaldehyde detoxification remains a worthy therapeutic strategy to prevent diabetic complications and other AGE-related disorders.

Differential effects of lipopolysaccharide on lipid peroxidation in F344N, SHR rats and BALB/c mice, and protection of melatonin and NAS against its toxicity

The effect of bacterial lipopolysaccharide (LPS) injection on the lipid peroxidation process in Fischer (F344N) rats, spontaneously hypertensive (SHR) rats, and BALB/c mice was studied. Lipid peroxidation, as measured by malondialdehyde + 4-hydroxyalkenals (MDA + HAE) levels, was decreased in brain, kidney, and liver homogenates of F344N rats injected with lower LPS doses of 0.5, 1.0, and 2.0 mg/kg, but was increased with the highest dose of 10 mg/kg body weight. The dose of 10 mg/kg LPS decreased the MDA + HAE levels in SHR brain homogenates and increased levels in the liver homogenates. MDA + HAE levels in the brain and liver but not kidney homogenates in BALB/c mice also increased after administration of LPS at the highest dose (10 mg/kg body weight). The effect of melatonin, N-acetylserotonin (NAS), and GR-135,531 (a melatonin ligand with high affinity for MT3 receptor) on the survival of BALB/c mice injected with lethal dose of LPS was also tested. A single dose of 5 mg/kg of melatonin or NAS simultaneously injected with LPS (25 mg/kg body weight) markedly protected mice from the lethal effect of LPS with survival rates of 90% and 95% for melatonin and NAS, respectively, and 59% for mice injected with just LPS after 24 hours; a survival rate of 50% for both melatonin and NAS, and 32% was obtained for mice injected with just LPS after five days. GR-135,531 did not show protection against a lethal dose of LPS. Our results indicated that the effect of LPS on lipid peroxidation is dose-, time-, and species-dependent, and that melatonin and NAS are equally effective in protecting mice from lethality caused by LPS.

Nitric oxide production by rat bronchoalveolar macrophages or polymorphonuclear leukocytes following intratracheal instillation of lipopolysaccharide or silica

Exposure of the lung to lipopolysaccharide (LPS) or silica results in an activation of alveolar macrophages (AMs), recruitment of polymorphonuclear leukocytes (PMNs) into bronchoalveolar spaces, and the production of free radicals. Nitric oxide (NO) is one of the free radicals generated by bronchoalveolar lavage (BAL) cell populations following either LPS or silica exposure. The purpose of the present study was to assess the relative contributions of AMs and PMNs to the amounts of NO produced by BAL cells following intratracheal (IT) instillation of either LPS or silica. Male Sprague Dawley rats (265-340 g body wt.) were given LPS (10 mg/100 g body wt.) or silica (5 mg/100 g body wt.). BAL cells were harvested 18-24 h post-IT and enriched for AMs or PMNs using density gradient centrifugation. Media levels of nitrate and nitrite (NOx; the stable decomposition products of NO) were then measured 18 h after ex vivo culture of these cells. Following IT exposure to either LPS or silica, BAL cell populations were approximately 20% AMs and approximately 80% PMNs. After density gradient centrifugation of BAL cells from LPS- or silica-treated rats, cell fractions were obtained which were relatively enriched for AMs (approximately 60%) or PMNs (approximately 90%). The amounts of NOx produced by the AM-enriched fractions from LPS- or silica-treated rats were approximately 2-4-fold greater than that produced by the PMN-enriched fractions. Estimations of the relative contribution of AMs or PMNs to the NOx produced indicated that: (i) following LPS treatment, 75%-89% of the NOx was derived from AMs and 11%-25% from PMNs; and (ii) following silica treatment, 76%-100% of the NOx was derived from AMs and 0-24% from PMNs. Immunohistochemistry for inducible NO synthase on lung tissue sections supported these findings. We conclude that AMs are the major source of the NO produced by BAL cells during acute pulmonary inflammatory responses to LPS or silica.

Nitric oxide released from iNOS in polymorphonuclear leukocytes makes them deformable in an autocrine manner

The objective of this study was to determine whether endogenous nitric oxide (NO) derived from reaction catalyzed by the inducible isoform of NO synthase (iNOS: NOS II) in polymorphonuclear leukocytes (PMNs) makes the PMNs deformable. Previous studies have shown that NO increases the deformability of PMNs and decreases the sequestration of PMNs in the lungs. However, there was little information regarding the effect of PMN-derived NO on the cells' deformability. In the present study PMNs were isolated from the blood of rats 24h after ip injection of saline (control) or lipopolysaccharide (LPS), and expression of iNOS in the PMNs of the LPS group was confirmed by immunocytochemistry. PMN deformability was evaluated by measuring the pressure generated during their passage through a microfilter at a constant flow rate. The nitrite/nitrate content of the solution in which the isolated PMNs were incubated was measured by the Griess method. In the control group, no iNOS was detectable in the PMNs, and the nitrite/nitrate level in the PMN incubation solution was low. Deformability was unchanged after incubation with specific iNOS inhibitor aminoguanidine, but decreased after incubation with N-formyl-methionyl-leucyl-phenyl-alanine. In the LPS group, PMN deformability was decreased compared to that of the control group. iNOS was detectable in the PMNs, and the deformability further decreased after incubation with aminoguanidine. These results suggest that endogenous NO generated during reactions catalyzed by iNOS in PMNs makes them deformable in an autocrine manner.

Mediators of peripheral blood neutrophilia induced by photodynamic therapy of solid tumors

Photodynamic therapy (PDT) of tumors elicits a strong host immune response and one of its manifestations is a pronounced neutrophilia. By blocking their function prior to Photofrin-based PDT of mouse EMT6 tumors, we have identified multiple mediators whose regulated action is responsible for this neutrophilia. In addition to complement fragments (direct mediators) released as a consequence of PDT-induced complement activation, there are at least a dozen secondary mediators that all arise as a result of complement activity. The latter include cytokines IL-1beta, TNF-alpha, IL-6, IL-10, G-CSF and KC, thromboxane, prostaglandins, leukotrienes, histamine, and coagulation factors.

Inducible nitric oxide synthase (iNOS) in endotoxemia: chimeric mice reveal different cellular sources in various tissues

The aim of these experiments was to determine the contribution of leukocyte-derived iNOS to total iNOS expression induced by lipopolysaccharide (LPS). By transferring bone marrow between iNOS+/+ and iNOS-/- mice, we created chimeric mice in which iNOS expression was limited to either circulating leukocytes (leukocyte-iNOS mice) or parenchymal cells (parenchyma-iNOS mice). Analysis of congenic markers demonstrated that >95% of thymocytes in chimeric mice were of donor origin. Also, following LPS treatment, iNOS mRNA was detectable in blood from leukocyte-iNOS mice but not parenchyma-iNOS mice. Together these findings indicated that the host marrow had been replaced entirely by donor cells. In the lung, at least 50% of the LPS-induced iNOS mRNA was derived from leukocytes, and immunohistochemical analysis indicated that leukocytes were the main source of iNOS protein. In contrast in the liver, colon, and muscle, iNOS expression was derived predominantly from parenchymal cells. This divergence is potentially explained by the high level of leukocyte recruitment to the lung, relative to the other tissues. Plasma levels of NOS byproducts indicated that parenchymal iNOS was the dominant source of systemic iNOS activity. These findings indicate that in tissues other than the lung, parenchymal cells are the principal source of iNOS during endotoxemia.

Intra-cochlear administration of dexamethasone attenuates aminoglycoside ototoxicity in the guinea pig

This study demonstrates the attenuation of aminoglycoside ototoxicity by cochlear infusion of dexamethasone (Dex) using a microcannulation-osmotic pump delivery system. The results indicate that treating the cochlea with Dex both before and after kanamycin administration was more effective in preventing ototoxicity than Dex treatment only after kanamycin administration. A concentration of 1 ng/ml Dex showed the greatest protective effect on both kanamycin-induced threshold shift of the auditory brainstem response and outer hair cell survival. These results show that the Dex treatment attenuates both functional and structural damage of the inner ear from aminoglycoside toxicity.

Nitric oxide- and oxygen-derived free radical generation from control and lipopolysaccharide-treated rat polymorphonuclear leukocyte

Previous studies from this lab have shown NO-mediated modulation of free radical generation from polymorphonuclear leukocytes (PMNs), following hypoxic-reoxygenation as well as in the normoxic cells. The present study is an attempt to investigate further the regulation of NO and free radical generation in the lipopolysaccharide (LPS)-treated PMNs. PMNs were isolated from the rat blood and peritoneal cavity, 4 h after LPS (1 mg/kg, i.p.) treatment. Nitric oxide synthase (NOS) activity and nitrite content were increased in the peripheral and peritoneal PMNs following LPS treatment. An increase in the apparent V(max) for l-arginine uptake was also observed in the LPS-treated peripheral PMNs, while peritoneal PMNs exhibited increase in both apparent V(max) and affinity for l-arginine. Synthesis of nitrite did not augment after increasing the availability of substrate to control PMNs, however, peripheral and peritoneal PMNs from LPS-treated rats utilized l-arginine more efficiently for nitrite synthesis. NOS activity, l-arginine uptake, and its utilization were maximal in the peritoneal PMNs. Arachidonic acid (AA, 1 x 10(-6) M)-induced free radical generation from PMNs was also enhanced significantly after LPS treatment. Preincubation of PMNs with nitrite elevated the free radical generation and myeloperoxidase (MPO) release. MPO and antioxidant enzyme activity in the PMNs was significantly augmented after LPS treatment. NOS inhibitors, aminoguanidine and 7-nitroindazole, inhibited arachidonic acid-induced free radical generation from LPS treated PMNs. The results obtained thus indicate that augmentation of free radical generation from rat PMNs following LPS treatment appears to be regulated by NO and MPO.

Nitric oxide mediates platelet activating factor-induced microvascular leakage in rat airways

Platelet activating factor (PAF), a highly potent chemical mediator in inflammation and allergic reactions, induces microvascular leakage in several tissues. In rat airways, PAF-induced microvascular leakage is probably mediated by an endothelial cell receptor in the microvessels. Nitric oxide (NO), first identified as endothelium-derived relaxing factor, has been suggested to be a mediator of airway microvascular leakage. However, the role of NO in PAF-induced microvascular leakage in the airways has not yet been established. The aim of this study was to investigate the role of NO in PAF-induced microvascular leakage in rat nasal mucosa and trachea. We injected PAF (1 microg/kg) intravenously, and the amount of PAF-induced microvascular leakage was measured with extravasation of Evans blue dye (30 mg/kg, injected intravenously 5 minutes before the injection of PAF) by means of spectrophotometry and fluorescence microscopy. Five Sprague-Dawley rats were pretreated with NG-nitro-L-arginine methyl ester (L-NAME; 10 mg/kg, intravenously injected 1 hour before the injection of PAF) to inhibit NO synthase, and control rats (n = 4) were pretreated with normal saline solution. The average amount of extravasated Evans blue dye was significantly lower in the L-NAME-pretreated rats than in the control rats (t-test, p < .01). Tissue sections of the L-NAME-pretreated rats clearly showed a decreased extravasation of Evans blue dye on fluorescence microscopy. In conclusion, pretreatment with L-NAME clearly inhibited PAF-induced microvascular leakage in the nasal mucosa and trachea of rats. This finding implies that PAF may activate the constitutive endothelial NO synthase in the microvessels, and that activated endogenous NO may mediate PAF-induced microvascular leakage in rat airways.

Modulation of polymorphonuclear leukocytes function by nitric oxide

Recognition of the endothelium-derived relaxation factor as nitric oxide (NO) gave rise to an impression that NO was synthesised only by the endothelial lining of the vessel wall. Later it was found that NO is synthesized constitutively by the enzyme nitric oxide synthase (NOS) in various cells. However, inflammatory cytokines can induce NOS (known as inducible NOS [iNOS]) activity in all the somatic cells. Blood cells, such as eosinophils, platelets, neutrophils, monocytes, and macrophages, also synthesize NO. Among them, polymorphonuclear leukocytes (PMNs) constitute an important proportion and are also the major participants in a number of pathological conditions with suggestive involvement of NO. PMNs can synthesize NO at rates similar to endothelial cells, thus suggesting the importance of PMN-derived NO in various physiological and pathological conditions. Most of the studies so far focus on the peripheral PMNs, while studies on PMNs after emigration are limited, thus warranting systematic studies on PMNs from both sources. The role of the endothelial NOS (eNOS) and functions of NO derived from the endothelial cells has been studied extensively. However, understanding of the PMNs NOS and its regulatory role in their function is unraveling. The present review summarizes the modulatory role of NO on PMNs functions and points out the discrepancies relating to presence of NOS in PMNs. This information will be helpful in understanding the importance of NO in physiological and pathological conditions associated with PMNs.

Expression of NOS II and its role in experimental small bowel ulceration in rats

BACKGROUND

Overproduction of nitric oxide (NO) has been implicated in the pathogenesis of experimental and clinical inflammatory bowel disease (IBD).

METHODS

We observed the expression and localization of inducible NO synthase (NOS-II) in small intestinal ulceration induced by indomethacin in rats. The role of NO was investigated by using NO synthase inhibitors.

RESULTS

The small intestine was affected by longitudinal ulcers after indomethacin administration and ulceration was associated with distinctive expression of NOS-II protein and mRNA. The amount of its expression was found to correlate with the extent of inflammation. Histologically, both immunohistochemistry and in situ hybridization revealed a similar localization of NOS-II to inflammatory and epithelial cells. The possible amelioration of the inflammation was modulated by aminoguanidine (AG) and NG-nitro-L-arginine methyl ester (L-NAME) treatment for 10 days. Both AG and L-NAME attenuated intestinal myeloperoxidase activity and gross inflammation, only AG was found to decrease intestinal permeability with a significant amelioration of body weight loss.

CONCLUSION

These findings indicate that NO derived mainly from inflammatory cells may play an important role in the pathophysiology of intestinal ulceration and offer the potential for future treatment directed at blocking neutrophils recruitment and NO overproduction in IBD.

Ethanol metabolism is not required for inhibition of LPS-stimulated transcription of inducible nitric oxide synthase

We examined the effect of inhibition of ethanol metabolism on ethanol-mediated suppression of Escherichia coli endotoxin (LPS-induced upregulation of transcription and release of inducible nitric oxide synthase (iNOS) and tumor necrosis factor alpha (TNFalpha) from rat alveolar macrophages (AM) in vivo. Ethanol (3.45 and 5.5 g/kg/IP) and t-butanol (3.7 g/kg, IP), given 30 min before intratracheal administration of LPS (1.0 mg/kg), inhibited the upregulation of iNOS mRNA and protein, determined by competitor equalized RT-PCR and Western immunoblot, respectively, but not TNFalpha mRNA in AM obtained 2 h after LPS administration by bronchoalveolar lavage (BAL). However, ethanol and t-butanol inhibited LPS-stimulated nitrate and nitrite (RNI) and TNFalpha protein in BAL fluid. Pretreatment of rats with 4-methylpyrazole (100 mg/kg, IP) 2 h before, or disulfiram 30 min before, administration of ethanol (3.45 g/kg, IP) failed to attenuate the inhibitory effect on iNOS mRNA or protein. t-Butyl hydroperoxide (100 mg/kg, IP) given to rats 30 min before administration of LPS enhanced LPS-mediated upregulation of iNOS mRNA and TNFalpha protein in AM and BAL fluid. The inhibitory effect of ethanol on iNOS mRNA was not mediated by an interaction with elevated levels of circulating corticosterone because pretreatment of rats with RU-38486 (100 mg/kg, IM), which inhibited prednisolone (50 mg/kg, IM), induced suppression of LPS-stimulated iNOS mRNA, and failed to attenuate ethanol-mediated inhibition of LPS-stimulated iNOS mRNA in AM. We conclude that metabolism of ethanol to acetaldehyde via alcohol dehydrogenase is not required for ethanol-mediated suppression of LPS-induced iNOS transcription and TNFalpha synthesis/release in AM. Moreover, an interaction of ethanol or acetaldehyde with circulating corticosterone is not involved in ethanol-mediated attenuation of LPS-stimulated iNOS mRNA or protein or TNFalpha protein in the lung. Speculatively, because oxidation of t-butanol to t-butylhydroperoxide results in activation, rather than inhibition, of iNOS and TNF-alpha, the reported ethanol-mediated enhancement of iNOS mRNA may result from the action of the hydroxyethyl radical.

Anti-Candida activity of calprotectin in combination with neutrophils or lactoferrin

The effect of an anti-microbial protein, calprotectin, in combination with neutrophils on the growth of Candida albicans was investigated. The growth inhibition of C. albicans by murine neutrophils was augmented by the addition of a low concentration of calprotectin prepared from rat peritoneal exudate cells. The concentrations of calprotectin causing 50% inhibition of growth of C. albicans in the absence or presence of neutrophils at an effector-to-target (E/T) ratio of 30 and 60 were estimated to be 0.45, 0.34 and 0.28 U/ml, respectively. The anti-Candida activity of calprotectin was completely inhibited by 2 microM of zinc ion, while it only partially lowered the activity of the combination of calprotectin and neutrophils. Lactoferrin, which is an anti-microbial protein released from neutrophils, strongly inhibited the growth of C. albicans in combination with calprotectin. These results suggest that calprotectin and lactoferrin released from neutrophils may cooperate to inhibit the growth of C. albicans at a local lesion of the infection where there is an accumulation of neutrophils.

Human and rat neutrophils constitutively express neural nitric oxide synthase mRNA

Freshly isolated rat circulating neutrophils (PMN) constitutively expressed neural nitric oxide synthase (nNOS) mRNA and nNOS protein and exhibited spontaneous basal release of low concentrations of nitrate and nitrite anion (RNI). In contrast, rat peripheral monocytes and macrophages were devoid of nNOS mRNA and protein and did not exhibit basal or spontaneous release of RNI. Constitutive neural NOS mRNA was also found in human PMN. However, nNOS protein was not expressed and spontaneous generation of RNI was absent in the human PMN. Spontaneous release of RNI from rat PMN was inhibited by 7-nitroindazole but not by L-N-iminoethyllysine, which further supported the nNOS origin of the spontaneously produced RNI. Intravenous administration of Escherichia coli endotoxin (0.6 mg/kg) did not acutely affect the content of nNOS mRNA or protein but inhibited nNOS-derived production of RNI in PMN and up-regulated iNOS mRNA and iNOS protein in PMN, macrophages, and monocytes. This communication demonstrates the existence of nNOS mRNA in rat and human PMN and nNOS protein in rat PMN. Moreover, the data also show that the nNOS system in rat PMN is functional and is inhibitable by the nNOS inhibitor 7-nitroindazole. These findings offer an explanation for the spontaneous formation of the PMN-derived relaxing factor resembling nitric oxide (NO). Moreover, since basal production of NO can affect expression of adhesion molecules and cell-cell binding, the nNOS system within the rat may play an important role in PMN function in normal and disease states. Finally and speculatively, if constitutively expressed nNOS mRNA is subject to activation and translation into nNOS protein, nNOS may also play a role in the function of human PMN.

Role of nitric oxide on diaphragmatic contractile failure in Escherichia coli endotoxemic rats

Contractile dysfunction of the respiratory muscles plays an important role in the genesis of respiratory failure during sepsis. Nitric oxide (NO), a free radical that is cytotoxic and negatively inotropic in the heart and skeletal muscle, is produced in large amounts during sepsis by a NO synthase inducible (iNOS) by LPS and/or cytokines. The aim of this study was to investigate whether iNOS was induced in the diaphragm of Escherichia coli endotoxemic rats and whether inhibition of iNOS induction or of NOS synthesis attenuated diaphragmatic contractile dysfunction. Rats were inoculated intravenously (IV) with 10 mg/kg of E. coli endotoxin (LPS animals) or saline (C animals). Six hours after LPS inoculation animals showed a significant increase in diaphragmatic NOS activity (L-citrulline production, P < 0.005). Inducible NOS protein was detected by Western-Blot in the diaphragms of LPS animals, while it was absent in C animals. LPS animals had a significant decrease in diaphragmatic force (P < 0.0001) measured in vitro. In LPS animals, inhibition of iNOS induction with dexamethasone (4 mg/kg IV 45 min before LPS) or inhibition of NOS activity with N(G)-methyl-L-arginine (8 mg/kg IV 90 min after LPS) prevented LPS-induced diaphragmatic contractile dysfunction. We conclude that increased NOS activity due to iNOS was involved in the genesis of diaphragmatic dysfunction observed in E. coli endotoxemic rats.

Changes in protein kinase C in early cardiomyopathy and in gracilis muscle in the BB/Wor diabetic rat

Hyperglycemia can upregulate protein kinase C (PKC), which may be an important mediator of the progression from normal heart and muscle function to diabetic myopathy in the myocardium and skeletal muscle in type 1 insulin-dependent diabetes mellitus (IDM). We evaluated this possibility during the early stage of IDM in BB/Wor diabetic (D) rats and age-matched BB/Wor diabetes-resistant (DR) rats. Interventricular septal thickness, E wave peak velocity of tricuspid inflow (both minimum and maximum), and left ventricular (LV) weight index were increased, and the rate of change in LV pressure (LV dP/dt) decreased in D rats subjected to M-mode and two-dimensional echocardiography and hemodynamic recording of heart rate, LV pressure (LVP), + LV dP/dt, -LV dP/dt, and LV end-diastolic pressure (LVEDP) in vivo and in vitro 41 days after the onset of hyperglycemia. Whole ventricle basal PKC activity was increased by 44.4 and 18.4% in the particulate and soluble fractions, respectively, from D rats compared with that from DR rats using r-32P phosphorylation of appropriate peptide substrates. When measured by Western blot gel densitometry, particulate PKC-alpha and PKC-delta content increased by 89 and 24%, respectively, but soluble PKC-beta and soluble and particulate PKC-epsilon were unchanged compared with that of DR rats. Similarly, gracilis muscle PKC activity and PKC-alpha and PKC-delta were elevated in the gracilis muscle, whereas that of the circulating neutrophil did not differ between the D and DR rats. Thus, in vivo, the early diabetic cardiomyopathy of the D rat is characterized by a restrictive LV with increased septal thickness and is associated with elevated PKC activity and increased amounts of myocardial particulate PKC-alpha and PKC-delta, which are also seen in the skeletal muscle. We conclude that increased PKC isozymes may play a pivotal role during IDM in the development of diabetic cardiomyopathy and skeletal muscle myopathy.

Nitric oxide synthase and cyclo-oxygenase pathways in the inflammatory response induced by zymosan in the rat air pouch

1. We have studied the participation of nitric oxide (NO) in an animal model of inflammation, the rat air pouch stimulated with zymosan. 2. Saline or zymosan was injected into 6-day rat air pouches at different time points and measurements were made of cell migration, levels of nitrite/nitrate (NO2/NO3-), prostaglandin E2 (PGE2), leukotriene B4 (L.TB4) and secretory phospholipase A2 (sPLA2) in exudates. Nitric oxide synthase (NOS) activity was determined in high speed supernatants from cells present in pouch exudates. Western blot analysis was also performed on these samples. 3. Zymosan injection induced a time-dependent increase in leukocyte infiltration, NO2/NO3- levels and cellular NOS activity that reached a peak by 8 h. Western blot analysis showed the same time course for induction of NOS protein. Colchicine administration to rats inhibited cellular infiltration and decreased the levels of NO metabolites and cellular NOS activity zymosan-injected air pouch at 8 h. NOS activity was present in polymorphonuclear leukocytes (PMNs) and monocytes, but not in the lymphocytes present in exudates. This enzyme is calcium-independent and needs NADPH for activity. PGE2 levels in exudates showed a time course inverse to that of NOS activity and NO metabolites, with maximum levels of PGE2 observed at 4 h after zymosan injection. 4. Administration of NG-nitro-L-arginine methyl ester (L-NAME) or aminoguanidine to rats significantly reduced cellular NOS activity, NO2/NO3- levels and chemiluminescence, whereas they were without effect on cell migration and degranulation, eicosanoid levels and sPLA2 activity. 5. Treatment of animals with dexamethasone inhibited cellular NOS activity, NO2/NO3- levels, chemiluminescence and the increase in the levels of PGE2 and LTB4, with only a weak effect on elastase release. 6. Administration of the selective cyclo-oxygenase-2 (COX-2) inhibitor NS398 to rats strongly reduced PGE2 levels in exudates without affecting NO metabolites or NOS activity at 4 h after zymosan injection. 7. Our data indicate that NOS is induced in the zymosan-stimulated rat air pouch model of inflammation. This enzyme is expressed in the cells migrating into the air pouch and caused an increased production of NO metabolites in exudates. The results also suggest the presence of an earlier phase in which eicosanoids play the main role, with participation of COX-2 activity, and a later phase mediated by NO. The endogenous release of NO does not modify prostaglandin biosynthesis in this in vivo model.

The involvement of nitric oxide in the anti-Candida albicans activity of rat neutrophils

Rat peritoneal neutrophils (PMN) spontaneously release nitric oxide (NO) when incubated in vitro. Addition of the NO synthase inhibitor L-monomethylarginine (L-NMMA) to the PMN reduces NO production and impairs the killing of the yeast Candida albicans, both effects being reversed by L-arginine. These data strongly suggest that oxidative metabolism of L-arginine by PMN is involved in the candidacidal activity of these cells. Rat blood PMN, which do not produce significant amounts of NO, exhibit a reduced killing capacity compared with peritoneal cells, except when they are obtained from lipopolysaccharide (LPS)-treated rats. In this case they produce measurable amounts of nitrite and express high fungicidal activity in vitro. Confirming the candidacidal activity of NO, the exposure of the C. albicans cultures to different concentrations of NO donors leads to a reduction in their survival. The candidacidal activity related to the NO pathway in rat PMN is phagocytosis dependent, since the activity can be inhibited by cytochalasin B. However, the oxidative products of oxygen released by rat PMN do not seem to be involved in their candidacidal activity, as incubation of the cells with phorbol myristate acetate (PMA) increases release of superoxide anion but does not affect the pattern of killing. Our results suggest that NO could be an important candidacidal pathway in rat neutrophils.

Ethanol suppresses endotoxin but not platelet activating factor-induced hypotension and nitric oxide

Ethanol (ETOH) inhibits the immune response to endotoxemia. The early stage of endotoxin (LPS)-induced shock is associated with an acute phase cardiovascular depression (APCD). Release of platelet activating factor (PAF) and tumor necrosis factor alpha (TNF alpha) with upregulation of nitric oxide (NO) production may initiate the APCD. Since ETOH inhibits induction of NO synthase (iNOS) mNRA by LPS, we postulate that ETOH may mask the APCD associated with endotoxemia. To test this, Sprague-Dawley rats (280-320 g, n = 5-6/group) were given LPS [0.75 mg/kg, intravenously (i.v.)] or PAF (10 to 150 micrograms/kg, i.v.) 30 min after administration of sterile saline (PBS), BN-5073 a mixed PAF antagonist (0.50 microgram/kg, i.v.), or ETOH [2.2-5.5 g/kg, intraperitoneally (i.p.)]. Cardiovascular parameters and plasma concentrations of nitrate and nitrite (RNI), ETOH, TNF alpha, and neutrophil (PMN) generation of RNI were measured. LPS and PAF both produced APCD. LPS-induced APCD was associated with tachycardia, elevated plasma TNF alpha and RNI, and ex vivo generation of RNI by PMNs. ETOH and BN-50730 prevented LPS-induced APCD and increases in RNI and TNF alpha. ETOH, however, increased the mortality associated with APCD. PAF produced only hypotension, bradycardia and elevated plasma levels of TNF alpha. ETOH and LNMMA did not affect PAF-induced APCD. BN-50730 inhibited PAF-induced APCD and plasma TNF alpha. We conclude that 1) ETOH inhibits the APCD and induction of NO characteristic of endotoxemia and 2) ETOH-induced suppression of LPS-mediated APCD may be mediated in part by suppression of release of intracellular PAF. Ethanol may increase the morbidity and mortality of endotoxemia by masking the hypotension and humoral changes characteristic of early endotoxemia thereby delaying appropriate therapy and by diminution of the protective effects of endogenous NO.

Cytokine-treated human neutrophils contain inducible nitric oxide synthase that produces nitration of ingested bacteria

Although the production of NO within rodent phagocytes is well-characterized, its production and function within human phagocytes are less clear. We show here that neutrophils within human buffy coat preparations stimulated with a mixture of interleukin 1, tumor necrosis factor alpha, and interferon gamma contain inducible NO synthase mRNA and protein, one of the enzymes responsible for NO production. The protein colocalizes with myeloperoxidase within neutrophil primary granules. Using an inhibitor of NO synthase, L-N-monomethyl arginine, we show that activity of this enzyme is required for the formation of nitrotyrosine around phagocytosed bacteria, most likely through the intermediate production of peroxynitrite, a reaction product of NO and superoxide anions.

Nitric oxide: a mediator of endotoxin-induced middle ear effusions

Using a rat model, the authors investigated the role of nitric oxide (NO) in endotoxin-induced middle ear effusion (MEE). After the eustachian tube was obstructed, the middle ear was transtympanically injected with 35 microL of either 1 mg/mL lipopolysaccharide (LPS) or LPS and 1 mmol/L N-nitro-L-arginine methyl ester (L-NAME), a competitive inhibitor of NO synthase. Over the next 6 hours, the fluid within the middle ear was collected every 2 hours, and the quantity of albumin in the fluid, an index of vascular leakage, was determined using enzyme-linked immunosorbent assay. L-NAME significantly reduced LPS-induced vascular extravasation into the middle ear. Inoculation of the ear with L-arginine, the substrate for NO synthase, reversed the effects of L-NAME. These results indicate that NO is a mediator of LPS-induced MEE. Therefore, inhibition of NO synthase may represent a novel approach to the treatment of otitis media with effusion.

Nitric oxide in inflammation and immune response

This short review deals with the role of a recently found signalling molecule, nitric oxide (NO), in inflammatory and immune responses. NO regulates inflammatory erythema and oedema and has cytotoxic action against micro-organisms. In some instances (such as reperfusion injury) NO has cytoprotective properties. Production of large amounts of NO by activated macrophages accounts for their ability to suppress lymphocyte proliferation. NO synthesis in lymphocytes is questionable but cytokines secreted by activated lymphocytes regulate NO synthesis by macrophages. Constitutive NO synthase is activated in neutrophils in response to inflammatory stimuli and NO has diverse, often biphasic effects on neutrophil functions. Increased concentrations of nitrite and nitrate (metabolites of NO) are present in arthritic joints. NO is synthesized not only by migrated inflammatory cells but also by articular chondrocytes and inflamed synovial membrane. In the inflamed joint, NO regulates the synthesis of several inflammatory mediators and functions of inflammatory cells. In addition, NO seems to mediate some destructive effects of proinflammatory cytokines such as interleukin-1. In conclusion, NO regulates several humoral and cellular responses in inflammation, having both anti-inflammatory and proinflammatory properties depending on the type and phase of the inflammatory reaction.

Chronic alcohol administration stimulates nitric oxide formation in the rat liver with or without pretreatment by lipopolysaccharide

This study examines the effect of chronic alcohol consumption on nitric oxide release from the liver of rats with or without lipopolysaccharide (LPS) (Escherichia coli) treatment. Reactive nitrogen intermediates (RNIs) in plasma were monitored with an NOx Analyzer, and nitric oxide (NO) production was measured as nitrite or nitrite + nitrate accumulation in perfusates of the perfused liver, and in supernatants of the freshly isolated hepatic cells after incubation for 3 hr in Hank's balanced salt solution buffer containing 1 mM L-arginine. RNI concentration in plasma of control rats was 32.0 +/- 3.4 microM (mean +/- SE). Livers from diet-fed control rats produced RNIs at the barely detectable rate of 7.8 +/- 1.5 nmol/hr x g wet liver. Six hr after administration of LPS (1 mg/kg, i.v.), plasma RNI levels in diet-fed control rats increased to 426.9 +/- 29.4 microM, and RNI release from the perfused liver was also markedly elevated to 97.7 +/- 7.7 nmol/hr x wet g liver, indicating hepatic NO release as a potentially important source for the increased RNI in plasma. The presence of NG-monomethyl-L-arginine (0.5-1 mM) or the absence of L-arginine in the perfusate inhibited LPS-induced stimulation of RNI release. EGTA (1 mM) had little effect, indicating that the increased RNI release was likely to be due to inducible NO synthase activity. The release of RNIs by freshly isolated Kupffer cells increased 13-fold, and this small cell mass contributed almost half of the hepatic RNI production under these conditions. Plasma ALT concentration was elevated after LPS administration, indicating incipient liver damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Ethanol suppresses Mycobacteria tuberculosis-induced mRNA for nitric oxide synthase in alveolar macrophages, in vivo

Acute ingestion of alcohol [ethanol (ETOH)] adversely affects the immunocompetence of both naive individuals as well as chronic alcohol abusers. An increased incidence and severity of tuberculosis is found in chronic alcohol abusers. Nitric oxide (NO) produced by alveolar macrophages (AMs) may play a role in the in vitro killing of Mycobacterium avium and Mycobacterium tuberculosis (MTB). Moreover, tumor necrosis factor-alpha (TNF-alpha) is believed to be a primary cytokine mediator of NO production by AMs. Recent studies from our laboratory demonstrated that ETOH suppressed endotoxin-induced increases in both TNF-alpha and NO in AMs, in vivo. We tested the postulate that acute ingestion of ETOH can interfere with mycobacteria-induced upregulation of the NO system in AMs, in vivo. We show that heat-killed M. avium complex (MAC) and human virulent MTB instilled into rat lungs rapidly increased mRNA for inducible NO synthase II (iNOS) of AMs in fluid obtained by bronchoalveolar lavage (BAL fluid). This was associated with production of reactive nitrogen intermediates [(RNIs); NO2- and NO3-] in BAL fluid, lung homogenate, and AMs in the absence of a significant increase in BAL fluid TNF-alpha. A single dose of ETOH (5.5 g/kg, ip) administered 30 min before intratracheal administration of MAC or MTB attenuated both MAC and MTB-induced increases in RNI in BAL fluid, lung, and AMs, and the increase in mRNA for iNOS. Thus, mycobacteria upregulate iNOS mRNA and enhance RNI production by AMs without any increase in the production of TNF-alpha. Moreover, ETOH attenuates mycobacteria-induced upregulation of mRNA for iNOS and RNI production in the absence of ETOH-mediated suppression of TNF. Speculatively, ETOH-mediated inhibition of the AM NO system may offer an explanation for the increased severity of mycobacterial infections in alcoholics.

Escherichia coli-induced inhibition of endothelium-dependent relaxation and gene expression and release of nitric oxide is attenuated by chronic alcohol ingestion

We examined the effect of chronic administration of ETOH on Escherichia coli-mediated suppression of relaxation and nitric oxide (NO) production by the rat thoracic aorta (RTA) and gene expression for constitutive NO synthase (cNOS) by the adrenal gland. Chronic alcoholic rats ("alcoholic") were fed a diet containing ETOH as 36% of the caloric intake for 8-10 weeks. Nonalcoholic control rats ("control") were fed an isocaloric equivalent diet containing 36% dextrin. Alcoholic rats were given an injection of approximately approximately 10(10) live E. coli through a dorsal SC catheter 24 and 19 h before experimentation ("alcoholic-septic"), and control rats were treated in an identical manner ("septic"). The next day the rats were anesthetized with ketamine-xylazine (0.1 ml/100 g rat) and rings of RTA were mounted in muscle chambers for isometric recording of force development. Rings of RTA were precontracted with an EC50 concentration of phenylephrine, and relaxation to acetylcholine (ACh), A23187, and nitroglycerin were obtained. A23187- and ACh-induced relaxation was attenuated in RTA obtained from septic rats, whereas the relaxation to nitroglycerin was slightly enhanced. Chronic administration of ETOH attenuated the effects of E. coli on endothelium-dependent relaxation in alcoholic-septic rats. NO was measured with ozone chemiluminescence. Basal and stimulated NO production was attenuated in RTA obtained from septic rats and unaffected in RTA obtained from alcoholic or alcoholic-septic rats. cNOS was unmeasurable in adrenals from septic rats. ETOH increased mRNA for cNOS, an effect amplified in alcoholic-septic rats. Thus, E. coli inhibits endothelium-dependent relaxation and NO production, and ETOH attenuates these effects of E. coli on the endothelium-NO system, possibly by upregulating gene expression for cNOS.