Inducible Nitric Oxide Synthase Inhibition Potentiates Multiple Organ Dysfunction Induced by Endotoxin in Conscious Rats

The renin-angiotensin system modulates endotoxic postconditioning of exacerbated renal vasoconstriction in preeclamptic offspring

We recently reported exacerbated endotoxic signs of neuroinflammation and autonomic defects in offspring of preeclamptic (PE) dams. Here, we investigated whether PE programming similarly modifies hemodynamic and renal vasoconstrictor responsiveness to endotoxemia in PE offspring and whether this interaction is modulated by gestational angiotensin 1-7 (Ang1-7). Preeclampsia was induced by gestational treatment with L-NAME. Adult offspring was challenged with lipopolysaccharides (LPS, 5 mg/kg) and systolic blood pressure (SBP) and renal vasoconstrictions were assessed 4 h later. Male, but not female, offspring of PE rats exhibited SBP elevations that were blunted by LPS. Renal vasoconstrictions induced by angiotensin II (Ang II), but not phenylephrine, were intensified in perfused kidneys of either sex. LPS blunted the heightened Ang II responses in male, but not female, kidneys. While renal expressions of AT1-receptors and angiotensin converting enzyme (ACE) were increased in PE offspring of both sexes, ACE2 was upregulated in female offspring only. These molecular effects were diminished by LPS in male offspring. Gestational Ang1-7 caused sex-unrelated attenuation of phenylephrine vasoconstrictions and preferentially downregulated Ang II responses and AT1-receptor and nuclear factor-kB (NFkB) expressions in females. Together, endotoxemia and Ang1-7 offset in sexually-related manners imbalances in renal vasoconstriction and AT1/ACE/ACE2 signaling in PE offspring.

The Bezold-Jarisch Reflex and The Inflammatory Response Modulation in Unanesthetized Endotoxemic Rats

Evidence indicates that the activation of the parasympathetic branch of the autonomic nervous system may be effective in treating inflammatory diseases. Previously, we have described that baroreflex activation displays anti-inflammatory properties. Analogous to the baroreflex, the Bezold-Jarisch reflex also promotes parasympathetic activation with simultaneous inhibition of the sympathetic system. Thus, the present study aimed to evaluate whether the activation of the Bezold-Jarisch reflex would also have the ability to reduce inflammation in unanesthetized rats. We used lipopolysaccharide (LPS) injection (5mg/kg, i.p.) to induce systemic inflammation in male Wistar Hannover rats and phenylbiguanide (PBG) administration (5μg/kg, i.v.) to activate the Bezold-Jarisch reflex. Spleen, heart, hypothalamus, and blood samples were collected to determine the levels of cytokines. Compared to baseline, PBG reduced the arterial pressure (115±2 vs. 88±5mmHg) and heart rate (380±7 vs. 114±26bpm), immediately after its administration, confirming the activation of the parasympathetic system and inhibition of the sympathetic system. From the immunological point of view, the activation of the Bezold-Jarisch reflex decreased the plasma levels of TNF (LPS: 775±209 vs. PBG + LPS: 248±30pg/ml) and IL-6 levels in the spleen (LPS: 39±6 vs. PBG + LPS: 24±4pg/mg of tissue). However, it did not change the other cytokines in the plasma or the other tissues evaluated. These findings confirm that the activation of the Bezold-Jarisch reflex can modulate inflammation and support the understanding that the cardiovascular reflexes regulate the immune system.

Extracellular heat shock protein HSC70 protects against lipopolysaccharide-induced hypertrophic responses in rat cardiomyocytes

We have recently shown that exogenous administration of extracellular heat shock protein HSC70, a previously recognized intracellular chaperone protein, can protect against LPS-induced cardiac dysfunction through anti-inflammatory actions. However, whether it can also exert anti-hypertrophic effect is unknown. The present study was aimed to investigate the efficacy of HSC70 against cardiac hypertrophy and its underlying molecular mechanisms. Cardiomyocytes were isolated from the cardiac ventricles of neonatal Wistar rats and LPS (1 μg/mL) was used to induce the hypertrophic responses. We found that HSC70 (0.1, 1 and 5 μg/mL) pretreatment attenuated LPS-induced cardiomyocyte hypertrophy dose-dependently. In addition, HSC70 mitigated LPS-induced inflammatory mediators including TNF-α, IL-6, NO, iNOS and COX-2, with down-regulated protein expression of MMP-2 and MMP-9. Moreover, HSC70 repressed LPS-induced signaling of MAPK and Akt. Finally, HSC70 inhibited NF-κB subunit p65, and the DNA binding activity of NF-κB. Taken together, these findings suggest that in vitro HSC70 can exert anti-hypertrophic effects through inhibition of pro-inflammatory mediators, which are potential mediated by the down-regulation of MAPK, Akt and NF-κB signaling pathways. In conclusion, extracellular HSC70 may be a novel pharmacologic strategy in the management of cardiac hypertrophy.

Time Course of Hemodynamic Responses to Different Doses of Lipopolysaccharide in Unanesthetized Male Rats

Lipopolysaccharide (LPS) administration is a well-known method to induce systemic inflammation widely used for investigating new therapeutic strategies for sepsis treatment, which is characterized by clinical manifestations such as tachycardia and hypotension. However, there are different doses of LPS used in several studies, and the hemodynamic responses were not always well characterized. Thus, the present study aimed to evaluate the arterial pressure, heart rate, heart rate variability, and baroreflex function from rats, over time, to different doses of LPS. Femoral artery and vein catheters were inserted into anesthetized Wistar-Hannover male rats for arterial pressure recording and LPS administration, respectively. On the next day, the arterial pressure was recorded before and after (90, 180, and 360 min) LPS injection (0.06, 20, 30, and 40 mg/kg). All doses of LPS tested increased the heart rate and decreased baroreflex sensitivity over time. In addition, while LPS administration of 20, 30, and 40 mg/kg increased the mean arterial pressure over time, 0.06 mg/kg decreased the mean arterial pressure at 360 min, as compared to baseline values. Furthermore, high doses of LPS decreased the power of the HF band of the cardiac interval spectrum over time, and the higher dose increased the power of the LF band. Our data indicate that high doses of LPS promote hypertensive response over time, while a low dose decreases arterial pressure. Moreover, the changes in heart rate variability and baroreflex function elicited by LPS may be not associated with arterial pressure response produced by the endotoxemia.

Sitagliptin attenuates inflammatory responses in lipopolysaccharide-stimulated cardiomyocytes via nuclear factor-κB pathway inhibition

Glucagon-like peptide-1 (GLP-1) and GLP-1 receptors (GLP-1Rs) are responsible for glucose homeostasis, and have been shown to reduce inflammation in preclinical studies. The aim of the present study was to determine whether sitagliptin, an inhibitor of the enzyme dipeptidyl peptidase-4 (DPP-4), as a GLP-1 receptor agonist, exerts an anti-inflammatory effect on cardiomyoblasts during lipopolysaccharide (LPS) stimulation. Exposure to LPS increased the expression levels of tumor necrosis factor (TNF)-α, interleukin-6 (IL)-6 and IL-1β in H9c2 cells, and also resulted in elevations in cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expression and nuclear factor-κB (NF-κB) nuclear translocation. Treatment with the DPP-4 inhibitor sitagliptin dose-dependently downregulated the mRNA levels of IL-6, COX-2 and iNOS in LPS-stimulated H9c2 cells. In addition, sitagliptin inhibited the increased protein expression of IL-6, TNF-α and IL-1β. NF-κB mRNA expression was reduced and its translocation to the nucleus was suppressed by treatment with sitagliptin. The present results demonstrated that sitagliptin exerts a beneficial effect on cardiomyoblasts exposed to LPS by inhibiting expression of inflammatory mediators and suppressing NF-κB activation. These findings indicate that the DPP-4 inhibitor sitagliptin may serve a function in cardiac remodeling attributed to sepsis-induced inflammation.

The effectiveness of heliox in acute respiratory distress syndrome

INTRODUCTION:

The management of acute respiratory distress syndrome (ARDS) was investigated with the use of heliox in an experimental model.

OBJECTIVES:

To investigate whether heliox can be considered a new therapeutic approach in ARDS.

METHODS:

ARDS was designed in Wistar albino male rats, 250-300 g in weight, by intratracheal instillation of physiological saline solution. Anesthezied and tracheotomized rats with ARDS were pressure-controlled ventilated. At the end of 210 min, helium gas was tried. All rats were assigned to two groups: Group 1 (n = 10) was the control group, and was given no treatment; group 2 (n = 7) was given heliox (He: O₂ = 50:50). The heliox group received heliox for 1 h continously. Rats were continued to be kept on a ventilator through the experiment. Two hours after the last inhalation, both lungs of the rats were excised for both histopathological examination and immunohistochemical evaluation.

STATISTICAL ANALYSIS USED:

Histopathological grading were expressed as median interquartile range. Mann–Whitney U-test was used to assess the relationships between the variables.

RESULTS:

The infiltation of neutrophils were decreased in rats treated with heliox. Edema in the interstitial and intraalveolar areas was less than that of the control rats. Also, the diminishing of perivascular and/or intraalveolar hemorrhage was apperant. Hyaline membrane (HM) formation decreased in the heliox group compared with the control group. Decreased inducible nitric oxide synthase expression was shown via immunohistochemical examination in the heliox group.

CONCLUSION:

The present study histopathologically indicated the effectiveness of heliox in the decreasing of neutrophil infiltation, interstitial/intraalveolar edema, perivascular and/or intraalveolar hemorrhage and HM formation in ARDS. Besides the known effect of heliox in obstructive lung disease, inhaled heliox therapy could be associated with the improvement of inflamation in ARDS.

Time course of liver nitric oxide concentration in early septic shock by cecal ligation and puncture in rats

An overwhelming nitric oxide (NO) production is a crucial step in the circulatory events as well as in the cellular alterations taking place in septic shock. However, evidences of this role arise from studies assessing the NO production on an intermittent basis precluding any clear evaluation of temporal relationship between NO production and circulatory alterations. We evaluated this relationship by using a NO specific electrode allowing a continuous measurement of NO production. Septic shock was induced by a cecal ligation and puncture (CLP) in a first group of anesthetized rats. After the same CLP, a second group received a selective iNOS inhibitor (L-NIL). Control rats were sham operated or sham operated with L-NIL administration. While NO concentration was measured every 2 min by a NO-sensitive electrode over 7h following CLP, the liver microcirculation was recorded by a laser-Doppler flowmeter. CLP induced a severe septic shock with hypotension occurring at a mean time of 240 min after CLP. At the same time, an increase in liver NO concentration was observed, whereas a decrease in microvascular liver perfusion was noted. In the septic shock group, L-NIL administration induced an increase in arterial pressure whereas the liver NO concentration returned to baseline values. In addition, shock groups experienced an increase in iNOS mRNA. These data showed a close temporal relationship between the increase in liver NO concentration and the microvascular alteration taking place in the early period of septic shock induced by CLP. The iNOS isoform is involved in this NO increase.

Hindlimb ischemia/reperfusion-induced remote injury to the small intestine: role of inducible nitric-oxide synthase-derived nitric oxide

Systemic inflammatory response syndrome, as a consequence of ischemia/reperfusion (I/R), negatively influences the function of the affected organs. The objective of this study was to assess the role of nitric oxide (NO) in remote intestinal inflammatory response elicited by hindlimb I/R. To this end, C57BL/6 (wild type; WT) and inducible nitric-oxide synthase (iNOS)-deficient mice were subjected to bilateral hindlimb ischemia (1 h) followed by 6 h of reperfusion. Some WT mice were injected with iNOS inhibitor N-[3-(aminomethyl)benzyl] acetamidine (1400W) (5 mg/kg s.c.) immediately before reperfusion, and proinflammatory response was assessed 6 h later. Hindlimb I/R resulted in dysfunction of the small intestine as assessed by the increase in permeability [blood-to-lumen clearance of Texas Red-dextran (molecular mass 3 kDa)] and an increase in the luminal levels of tumor necrosis factor (TNF)-alpha protein and nitrate/nitrite (NO(2)(-)/NO(3)(-)). The above-mentioned changes were accompanied by up-regulation of the proinflammatory phenotype in the mucosa of small intestine with respect to 1) an increase in TNF-alpha and iNOS protein expression, 2) leukocyte accumulation, 3) formation of edema, 4) an increase in leukocyte rolling/adhesion in the submucosal microvasculature, and 5) activation of transcription factor nuclear factor-kappaB and up-regulation of adhesion molecule expression. Interestingly, the most profound changes with respect to intestinal dysfunction were found in jejunum and ileum, whereas duodenum was affected the least. Interfering with iNOS activity (1400W and iNOS-deficient mice) significantly attenuated hindlimb I/R-induced inflammatory response and dysfunction of the small intestine with respect to the above-mentioned markers of inflammation. The obtained results indicate that hindlimb I/R induces remote inflammatory response in the small intestine through an iNOS-derived NO-dependent mechanism.

Endotoxin-induced gene expression differences in the brain and effects of iNOS inhibition and norepinephrine

PURPOSE

We studied gene expression differences in brain homogenate, hippocampus, somatosensory cortex and cerebellum of rats suffering from sepsis-associated delirium and analyzed the effects of norepinephrine and 1,400 W (specific inhibitor of the inducible nitric-oxide synthase).

METHODS

We applied microarray screenings to rat brain homogenate 1, 3 and 4.5 h after lipopolysaccharide (LPS, 5 mg/kg) or 0.9% NaCl treatment. Therapy groups were analyzed after 4.5 h. Validations and compartment specific investigations were carried out by real-time PCR.

RESULTS

Most striking gene expression differences were seen 4.5 h after LPS administration, especially within the hippocampus (chemokines and endothelial cell-specific molecule 1). Norepinephrine resulted in a discrete chemokine up-regulation, while 1,400 W had hardly any effect.

CONCLUSION

Strongest gene regulations were found within the hippocampus. Norepinephrine showed a tendency of having a proinflammatory influence, while 1,400 W had no clear-cut effect onto the gene expression level.

Changes of midazolam pharmacokinetics in Wistar rats treated with lipopolysaccharide: relationship between total CYP and CYP3A2

It has been reported that infection interferes with drug metabolism, resulting in changes in pharmacokinetics. In this study, we investigated the effects of lipopolysaccharide (LPS) on hepatic total cytochrome P450 (CYP), CYP3A2, and CYP2C11 contents in a transient, LPS-induced, endotoxemia model of rats. In addition, to assess the effects on CYP3A2 activities, the pharmacokinetics of midazolam (CYP3A2 substrate) and 1-OH-midazolam (metabolite of midazolam) were investigated. Hepatic total CYP contents were significantly low until day 3 ( P < 0.05) but returned to the control level on day 5. Hepatic CYP3A2 contents were significantly decreased on day 1 until day 5 ( P < 0.05) but returned to the control level on day 7. Hepatic CYP2C11 contents were continuously low until day 7, and lowest on day 3. The AUC of 1-OH-midazolam was significantly decreased on day 1 after LPS administration ( P < 0.01). In conclusion, LPS (5 mg/kg) challenge decreased hepatic total CYP, CYP3A2, and CYP2C11 contents and also decreased the activities of hepatic CYP3A2. It took at least 7 days for hepatic total CYP and CYP3A2 to recover to control levels, and it was suggested that the changes of hepatic total CYP contents might correlate with those of hepatic CYP3A2 contents and activities. Additionally, it is shown that their changes might reflect the recovery process from inflammation.

Time-limited hyporesponsiveness to inhaled nitric oxide and pulmonary phosphodiesterase activity in endotoxemic rats

In acute lung injury (ALI) pulmonary hyporesponsiveness to inhaled nitric oxide (iNO) still represents an unresolved clinical challenge. In septic ALI-patients the incidence of hyporesponsiveness to iNO is increased; therefore, endotoxemia appears to play a major role. Experimental data suggest that endotoxemia, e.g., induced by lipopolysaccharides (LPS), contribute to the hyporesponsiveness to iNO. Guanosine 3',5'-cyclic monophosphate (cGMP) is metabolized by phosphodiesterases (PDE). The role of PDE in reduced pulmonary vascular response in experimental endotoxemia is still not known. Here, we hypothesized that PDE activity modulates initial pulmonary responsiveness to iNO in ALI following systemic endotoxin exposure. Rats were treated with LPS or used as controls. Lungs were isolated-perfused 0-36 h after LPS injection and the synthetic thromboxane analogue U46619 was added to increase pulmonary artery pressure by 6-8 mmHg (n = 47). Then, the pulmonary vasodilatory response to 3 doses of iNO (0.4, 4 and 40 ppm) was measured. Furthermore, lungs were prepared as described previously, and 2, 10, and 18 h after LPS the change in pulmonary artery pressure in response to two different inhibitors of PDE, one of which is PDE sensitive (8-Br-cGMP) and one is PDE stable (8-pCPT-cGMP), was determined (n = 43). Serum nitrite/nitrate levels started to increase 4 h after LPS, with a maximum at 18 h. In contrast, decreased pulmonary vasoreactivity in response to iNO developed as early as 2 h later and remained depressed up to 18 h. The pulmonary vasoreactivity to the PDE-sensitive 8-Br-cGMP after LPS-stimulation was lower than that in lungs treated with the PDE-stable 8-pCPT-cGMP. In rats pretreated with LPS, hyporesponsiveness of pulmonary vessels to iNO is time-limited and associated with increased serum nitrite/nitrate levels, and appears to be attributed in part to increased pulmonary PDE activity.

Inducible nitric oxide synthase and heme oxygenase-1 in the lung during lipopolysaccharide tolerance and cross tolerance

OBJECTIVE

Pretreatment with low-dose lipopolysaccharide protects cells/organs against a subsequent lethal Gram-negative (lipopolysaccharide tolerance) or Gram-positive (cross tolerance) stimulus. We determined whether this occurs in the rat lung. The involvement of inducible nitric oxide synthase and heme oxygenase-1 was evaluated.

DESIGN

Laboratory study.

SETTING

University hospital laboratory.

SUBJECTS

Anesthetized male Wistar rats.

INTERVENTIONS

To test the hypothesis, rats received saline or lipopolysaccharide (1 mg/kg). At 2, 4, 8, 16, or 24 hrs later, blood samples and lung tissue were taken to determine messenger RNA, protein concentration, and activity of inducible nitric oxide synthase and heme oxygenase-1. In additional experiments, rats were challenged with lipopolysaccharide (1 mg/kg) and subjected to Gram-negative (lipopolysaccharide) or Gram-positive (lipoteichoic acid and peptidoglycan) shock 24 hrs later. These studies were carried out in the presence and absence of inducible nitric oxide synthase or heme oxygenase-1 inhibitors (1400W or tin protoporphyrin IX). Following 6 hrs of shock, lung tissue was taken to determine lung damage and heme oxygenase-1 concentration and activity.

MEASUREMENTS AND MAIN RESULTS

In the rat lung, lipopolysaccharide (1 mg/kg) induced a significant increase in inducible nitric oxide synthase protein at 8 hrs with a corresponding increase in plasma nitrate/nitrite at 8-16 hrs. Simultaneously, heme oxygenase-1 messenger RNA transcripts were observed at 8-16 hrs, and maximal expression of the protein followed (24 hrs). Pretreatment with low-dose lipopolysaccharide reduced myeloperoxidase activity (neutrophil infiltration) and wet-dry ratio (pulmonary edema) in the lungs of animals subjected to Gram-negative or Gram-positive shock, demonstrating tolerance. Pretreatment with low-dose lipopolysaccharide and the selective inducible nitric oxide synthase inhibitor 1400W reduced heme oxygenase-1 protein expression, and lung protection was abolished. Tin protoporphyrin IX did not affect heme oxygenase-1 expression, but heme oxygenase activity and lung protection were significantly reduced.

CONCLUSIONS

We propose that nitric oxide (most likely inducible nitric oxide synthase derived) regulates the induction of heme oxygenase-1 in the lung, which in turn plays an important part in pulmonary protection during lipopolysaccharide tolerance and cross tolerance.

Nitric oxide modulates air embolism-induced lung injury in rats with normotension and hypertension

1. Air embolism the in lungs induces microvascular obstruction, mediator release and acute lung injury (ALI). Nitrite oxide (NO) plays protective and pathological roles in ALI produced by various causes, but its role in air embolism-induced ALI has not been fully investigated. 2. The purpose of the present investigation was to elucidate the involvement of NO and pro-inflammatory cytokines in the pathogenesis of ALI following air infusion into isolated perfused lungs from spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKY) rats. 3. The extent of ALI was evaluated by changes in lung weight, Evans blue dye leakage, the protein concentration in the bronchoalveolar lavage and pathological examination. We also measured nitrite/nitrate (NO(x)), tumour necrosis factor (TNF)-alpha and interleukin (IL)-1beta concentrations in lung perfusate and determined cGMP in lung tissue. 4. The NO synthase (NOS) inhibitors N(G)-nitro-l-arginine methyl ester (l-NAME) and l-N(6)-(1-iminoethyl)-lysine (l-Nil), as well as the NO donors sodium nitroprusside (SNP) and s-nitroso-N-acetylpenicillamine (SNAP), were administered 30 min before air embolism at a concentration of 10(-3) mol/L in the lung perfusate. 5. Air embolism-induced ALI was enhanced by pretreatment with l-NAME or l-Nil, but was alleviated by SNP or SNAP pretreatment, in both SHR and WKY rats. In both SHR and WKY rats, AE elevated levels of NO(x) (2.6 and 28.7%, respectively), TNF-alpha (52.7 and 158.6%, respectively) and IL-1beta (108.4 and 224.1%, respectively) in the lung perfusate and cGMP levels in lung tissues (35.8 and 111.2%, respectively). Pretreatment with l-LAME or l-Nil exacerbated, whereas SNP or SNAP abrogated, the increases in these factors, except in the case of NO(x) (levels were decreased by l-LAME or l-Nil pretreatment and increased by SNP or SNAP pretreatment). 6. Air embolism caused increases in the lung weight (LW)/bodyweight ratio, LW gain, protein concentration in bronchoalveolar lavage and Evans blue dye leakage. These AE-induced changes were less in lungs isolated from SHR compared with normotensive WKY rats. 7. The results suggest that ALI and associated changes following air embolism in lungs isolated from SHR are less than those in WKY rats. Nitric oxide production through inducible NOS isoforms reduces air embolism-induced lung injury and associated changes. Spontaneously hypertensive rats appear to be more resistant than WKY rats to air embolism challenge.

Niacinamide abrogates the organ dysfunction and acute lung injury caused by endotoxin

Poly (ADP-ribose) synthabse (PARS) or polymerase (PARP) is a cytotoxic enzyme causing cellular damage. Niacinamide inhibits PARS or PARP. The present experiment tests the effects of niacinamide (NCA) on organ dysfunction and acute lung injury (ALI) following lipopolysaccharide (LPS). LPS was administered to anesthetized rats and to isolated rat lungs. In anesthetized rats, LPS caused systemic hypotension and increased biochemical factors, nitrate/nitrite (NOx), methyl guanidine (MG), tumor necrosis factoralpha (TNFalpha), and interleukin-1beta (IL-1beta). In isolated lungs, LPS increased lung weight (LW) to body weight ratio, LW gain, protein and dye tracer leakage, and capillary permeability. The insult also increased NOx, MG, TNFalpha, and IL-1beta in lung perfusate, while decreased adenosine triphosphate (ATP) content with an increase in PARP activity in lung tissue. Pathological examination revealed pulmonary edema with inflammatory cell infiltration. These changes were abrogated by posttreatment (30 min after LPS) with NCA. Following LPS, the inducible NO synthase (iNOS) mRNA expression was increased. NCA reduced the iNOS expression. Niacinamide exerts protective effects on the organ dysfunction and ALI caused by endotoxin. The mechanisms may be mediated through the inhibition on the PARP activity, iNOS expression and the subsequent suppression of NO, free radicals, and proinflammatory cytokines with restoration of ATP.

The detrimental role of inducible nitric oxide synthase in the pulmonary edema caused by hypercalcemia in conscious rats and isolated lungs

We aim to test the hypothesis that hypercalcemia produces pulmonary edema (PE) and to elucidate the mechanism. Experimentations were carried out in conscious rats and isolated perfused rat lungs. We evaluated PE by lung weight changes, protein concentration in bronchoalveolar lavage, dye leakage, and microvascular permeability. Plasma nitrate/nitrite, methyl guanidine (MG), proinflammatory cytokines, procalcitonin levels, and histopathological examinations were evaluated. Immunochemical staining and reverse-transcriptase polymerase chain reaction (RT-PCR) were used to detect inducible nitric oxide synthase (iNOS) and endothelial NOS (eNOS) in the lungs. Hypercalcemia was produced in the conscious rat and isolated perfused lungs. Calcitonin and L-N(6) (1-iminoethyl)-lysine (L-Nil) were administered before hypercalcemia to observe their effects. Hypercalcemia caused severe PE in rats. Pathological and immunochemical examinations revealed hemorrhagic edema with iNOS activity in the alveolar macrophages and epithelial cells. RT-PCR showed an increase in iNOS mRNA expression. Hypercalcemia increased nitrate/nitrite, MG, proinflammatory cytokines and procalcitonin levels. Pretreatment with calcitonin or L-Nil prevented these changes. In conclusion, hypercalcemia caused PE in conscious rats and isolated perfused rat lungs. The increases in nitrate/nitrite, free radicals, proinflammatory cytokines, procalcitonin and iNOS activity suggest that hypercalcemia induces a sepsis-like syndrome. The effect of hypercalcemia on the lung may involve iNOS and NO.

Endotoxin-induced acute lung injury and organ dysfunction are attenuated by pentobarbital anaesthesia

1. Acute lung injury (ALI) as a result of sepsis is a major cause of mortality. Certain anaesthetic agents have been reported to suppress pro-inflammatory cytokines and inducible nitric oxide (NO) synthase (iNOS) activities. We investigated the effects of pentobarbital on ALI and organ functions after the administration of endotoxin. 2. Intravenous (i.v.) pentobarbital (20 or 40 mg/kg) was administered 5 min after lipopolysaccharide (LPS; 10 or 30 mg/kg via i.v. infusion). To avoid hypoxia and/or hypercapnia following anaesthesia, we installed a special chamber connected to a rodent ventilator to provide ventilation with 95% oxygen content and 5% nitrogen. The animal was kept at eucapnic conditions (arterial PCO2 at an average of 38 +/- 2 mmHg). 3. We monitored the arterial pressure (AP) and heart rate (HR). Acute lung injury was evaluated by lung weight changes, protein concentration in bronchoalveolar lavage, and Evans blue leakage. Plasma nitrate/nitrite, methyl guanidine and biochemical factors were determined. Pathological and immunofluorescent examinations were performed to observe the lung changes and to determine the activities of pro-inflammatory cytokines, nitrotyrosine and iNOS. 4. Lipopolysaccharide caused dose-dependent systemic hypotension with an increase in the extent of ALI. The lung pathology included oedema and inflammatory cell infiltration. Accompanying the ALI, LPS elevated plasma nitrate/nitrite, methyl guanidine, blood urea nitrogen, lactic dehydrogenase, creatinine phosphokinase, glutamic transaminase and amylase. The lung tissue content of tumour necrosis factor-alpha, interleukin-lbeta, iNOS and nitrotyrosine was increased following LPS administration. These changes were abrogated by pentobarbital anaesthesia. 5. Our results indicated that pentobarbital anaesthesia significantly augmented the LPS-induced systemic hypotension. However, it attenuated the LPS-induced ALI and organ dysfunctions. This agent also improved the survival rate following LPS at high and low doses. This mechanism may be related to the inhibitory effects on the increases in the production or activity of NO, free radicals, pro-inflammatory cytokines, nitrotyrosine and iNOS.

Inhibition of inducible nitric oxide synthase attenuates acute endotoxin-induced lung injury in rats

1. In the present study, we investigated the effects of the inducible nitric oxide (iNOS) inhibitors S-methylisothiourea (SMT) and l-N(6)-(1-iminoethyl)-lysine (l-Nil) on endotoxin-induced acute lung injury (ALI), as well as the associated physiological, biomedical and pathological changes, in anaesthetized Sprague-Dawley rats and in rat isolated perfused lungs. 2. Endotoxaemia was induced by an intravenous (i.v.) infusion of lipopolysaccharide (LPS; Escherichia coli 10 mg/kg). Lipopolysaccharide produced systemic hypotension and tachycardia. It also increased the lung weight/bodyweight ratio, lung weight gain, exhaled nitric oxide (NO), the protein concentration in bronchoalveolar lavage and microvascular permeability. 3. Following infusion of LPS, plasma nitrate/nitrite, methyl guanidine, pro-inflammatory cytokines (tumour necrosis factor-alpha and interleukin-1beta) were markedly elevated. Pathological examination revealed severe pulmonary oedema and inflammatory cell infiltration. Pretreatment with SMT (3 mg/kg, i.v.) or l-Nil (3 mg/kg, i.v.) significantly attenuated the LPS-induced changes and ALI. 4. The results suggest that the inflammatory responses and ALI following infusion of LPS are due to the production of NO, free radicals and pro-inflammatory cytokines through the iNOS system. Inhibition of iNOS is effective in mitigating the endotoxaemic changes and lung pathology. Inhibitors of iNOS may be potential therapeutic agents for clinical application in patients with acute respiratory distress syndrome.

Exercise training attenuates septic responses in conscious rats

PURPOSE

To evaluate the effects of exercise training on the changes induced by endotoxin in arterial pressure, heart rate (HR), blood cells, biochemical factors, plasma nitrite/nitrate, methyl guanidine (MG), proinflammatory cytokines, and pathology of the heart, liver, and lung.

METHODS

Twenty-four 10-wk-old male Wistar-Kyoto rats weighing 320-350 g were randomly assigned into two groups. The exercise-trained group (Tr; N = 12) received exercise training for 4 wk. The control (Con) group was placed on the treadmill and remained sedentary for the same time period. Endotoxemia was induced by intravenous (i.v.) infusion of lipopolysaccharide (LPS; 10 mg.kg(-1)) for 20 min, after which the animals were observed for 72 h. The femoral artery was cannulated to monitor arterial pressure and HR. Blood samples were collected 1 h before and at various times after LPS infusion. We determined plasma nitrite/nitrate, MG, white blood cells, neutrophils, lymphocytes, red blood cells, blood urea nitrogen, creatinine (Cr), aspartate aminotransferase, alanine aminotransferase, lactic acid dehydrogenase, creatine phosphokinase, amylase, lipase, tumor necrosis factor(alpha), and interleukin-1(beta). The heart, liver, and lung were taken for pathological examination and assessment after the experiment.

RESULTS

The Tr group had lower basal levels of arterial pressure, HR, MG, neutrophils, and Cr than the Con group. Exercise training attenuated the LPS-induced decreases in blood cells. After LPS administration, plasma levels of nitrate/nitrite, MG, biochemical factors, and proinflammatory cytokines in the Con group were higher than in the Tr group. Pathological examination and assessment revealed that cardiac, hepatic, and pulmonary injury were more severe in the Con group than in the Tr group.

CONCLUSIONS

Exercise training attenuates septic responses and protects organs from damage in sepsis.

Responsiveness to inhaled NO in isolated-perfused lungs from endotoxin-challenged rats is dependent on endogenous nitrite/nitrate synthesis

BACKGROUND AND OBJECTIVES

In isolated-perfused lungs of lipopolysaccharide (LPS)-challenged rats, vasodilatation to inhaled nitric oxide (NO) is impaired. Inhibition of nitric oxide synthase 2 (NOS2) by aminoguanidine (AG) prevented hyporesponsiveness to inhaled NO. Here, we investigated whether NOS2-mediated nitrite/nitrate synthesis modulates responsiveness to inhaled NO.

METHODS

Sprague-Dawley rats received intraperitoneally 0.5 mg kg(-1) LPS. Four hours later, LPS-treated rats received 3, 10 or 30 mg kg(-1) AG or 0.01, 0.1 or 1 mg kg(-1) S-methylisothiourea (SMT) by intraperitoneal injection. Sixteen to eighteen hours later, lungs were isolated and perfused, and pulmonary artery pressure (PAP) was elevated by 6-8 mmHg using the thromboxane analogue U46619. The decrease of PAP in response to inhaled NO and nitrate/nitrite levels in serum and perfusate was measured.

RESULTS

In rats treated with LPS alone or 0.01 or 0.1 mg kg(-1) SMT, 40 ppm NO decreased PAP less than in rats treated with AG and 1 mg kg(-1) SMT (-1.8 mmHg (95% confidence interval: -1.5 to -2.1) vs. -6.0 mmHg (-5.7 to -6.3), P < 0.01). Improved NO responsiveness was associated with lower serum and perfusate nitrite/nitrate levels than in rats with hyporesponsiveness to inhaled NO (102 micromol (82-122) vs. 282 micromol (261-303) and 8.1 micromol (6.9-9.3) vs. 19.8 micromol (17.2-22.4), respectively, P < 0.01).

CONCLUSIONS

These observations demonstrate that in isolated-perfused lungs of LPS-treated rats, NOS2 inhibition improved responsiveness to inhaled NO. Here, responsiveness to inhaled NO is dependent on the ability of NOS2 inhibitors to reduce nitrite and nitrate levels in serum and released in the lung.

Endotoxin-induced acute lung injury is enhanced in rats with spontaneous hypertension

1. Acute lung injury (ALI), or acute respiratory distress syndrome, is a major cause of mortality in endotoxaemia. The present study tested whether the endotoxaemia-induced changes and associated ALI were enhanced in rats with established hypertension and to examine the possible mechanisms involved. 2. Fifty spontaneously hypertensive rats (SHR) and the same number of normotensive Wistar Kyoto (WKY) rats, aged 12-15 weeks, were used. The experiments were performed in conscious, unanaesthetized rats. Endotoxaemia was produced by intravenous lipopolysaccharide (LPS; 10 mg/kg). N(G)-Nitro-L-arginine methyl ester (L-NAME; 10 mg/kg, i.v.), L-N(6)-(1-iminoethyl)-lysine (L-Nil; 5 mg/kg, i.v.) and 3-morpholinosydnonimine (SIN-1; 5 mg/kg, i.v.) were given 5 min before LPS to observe the effects of nitric oxide synthase (NOS) inhibition and nitric oxide (NO) donation. 3. We monitored arterial pressure and heart rate and evaluated ALI by determining the lung weight/bodyweight ratio, lung weight gain, leakage of Evans blue dye, the protein concentration in bronchoalveolar lavage and histopathological examination. Plasma nitrate/nitrite, methyl guanidine, pro-inflammatory cytokines, including tumour necrosis factor-alpha and interleukin-1beta, and lung tissue cGMP were determined. Expression of mRNA for inducible and endothelial NOS was examined using reverse transcription-polymerase chain reaction. 4. Lipopolysaccharide caused systemic hypotension, ALI and increases in plasma nitrate/nitrite, methyl guanidine, pro-inflammatory cytokines and lung cGMP content. The LPS-induced changes were greater in SHR than in WKY rats. Pretreatment with L-NAME or L-Nil attenuated, whereas the NO donor SIN-1 aggravated, the endotoxin-induced changes. 5. In conclusion, rats with genetic hypertension are more susceptible to endotoxaemia and this results in a greater extent of ALI compared with normotensive WKY rats.

Propofol exerts protective effects on the acute lung injury induced by endotoxin in rats

Acute lung injury (ALI) is a major culprit of mortality in endotoxemia. Propofol has been commonly used in critical ill patients for sedation. This experiment attempted to elucidate the effects and possible mechanisms of propofol on the ALI induced by endotoxin. Experimentations were carried out using anesthetized, ventilated rats and isolated perfused rat lungs. Endotoxemia was induced by intravenous lipopolysaccharide (LPS, 10 mg kg(-1)). Various groups of rats received infusion of physiological saline solution (PSS) and LPS. Five min after LPS, propofol at low dose (5 mg kg(-1)h(-1)) or high dose (10 mg kg(-1)h(-1)) was infused for 6h. In isolated perfused rat lungs, PSS, LPS, and propofol (30 or 60 mg kg(-1)) were added into the perfusion circuit. During or after 6h observation, we determined the lung weight (LW)/body weight ratio, LW gain, exhaled nitric oxide (NO) and protein concentration in broncheoalveolar lavage. Lung pathology was evaluated to quantify the lung injury score. Plasma nitrate/nitrite, methyl guanidine (MG), tumor necrosis factor(alpha), and interleukin-1(beta) were examined. Blood leukocytes were counted. Capillary filtration coefficient (K(fc)) was obtained in isolated perfused lungs. Posttreatment of propofol at low or high dose attenuated or prevented the extent of ALI. It also reduced the plasma nitrate/nitrite, MG, and pro-inflammatory cytokines including tumor necrosis factor(alpha) (TNF(alpha)) and interleukin-1(beta) (IL-1(beta)). In the isolated perfused rat lungs, propofol significantly reduced the LPS-induced increase in K(fc). This agent did not affect the leukocytopenia caused by LPS. Accordingly, the effects of propofol on the ALI were not related to leukocyte activation or sequestration. Our results suggest that propofol exerts protective effect on the endotoxin-induced ALI. The mechanisms of actions may be mediated through inhibition on the release of pro-inflammatory cytokines, free radicals and NO. In addition, propofol abrogates the microvascular leakage of water and protein in the lungs. The results imply that the use of propofol in critically ill is not only for sedation, but also useful for the prevention of inflammatory progression and lung damage.

N-acetylcysteine abrogates acute lung injury induced by endotoxin

1. Acute lung injury (ALI) or acute respiratory distress syndrome is a serious clinical problem with high mortality. N-Acetylcysteine (NAC) is an anti-oxidant and a free radical scavenger. It has been reported recently that NAC ameliorates organ damage induced by endotoxin (lipopolysaccharide; LPS) in conscious rats. The present study was designed to evaluate the effects of NAC on LPS-induced ALI and other changes in anaesthetized rats. 2. Sprague-Dawley rats were anaesthetized with pentobarbital (40 mg/kg, i.p.). Endotracheal intubation was performed to provide artificial ventilation. Arterial pressure and heart rate were monitored. The extent of ALI was evaluated with the lung weight (LW)/bodyweight ratio, LW gain, exhaled nitric oxide (NO) and protein concentration in bronchoalveolar lavage (PCBAL). Haematocrit, white blood cells, plasma nitrate/nitrite, methyl guanidine (MG), tumour necrosis factor (TNF)-alpha and interleukin (IL)-1b were measured. Pathological changes in the lung were examined and evaluated. 3. Endotoxaemia was produced by injection of 10 mg/kg, i.v., LPS (Escherichia coli). Animals were randomly divided into three groups. In the vehicle group, rats received an i.v. drip of physiological saline solution (PSS) at a rate of 0.3 mL/h. The LPS group received an i.v. drip of PSS for 1 h, followed by LPS (10 mg/kg by slow blous injection, i.v., over 1-2 min). Rats in the LPS + NAC group received NAC by i.v. drip at a rate of 150 mg/kg per h (0.3 mL/h) for 60 min starting 10 min before LPS administration (10 mg/kg by slow blous injection, i.v., over 1-2 min). Each group was observed for a period of 6 h. 4. N-Acetylcysteine treatment improved the LPS-induced hypotension and leukocytopenia. It also reduced the extent of ALI, as evidenced by reductions in LW changes, exhaled NO, PCBAL and lung pathology. In addition, NAC diminished the LPS-induced increases in nitrate/nitrite, MG, TNF-a and IL-1b. 5. In another series of experiments, LPS increased the mortality rate compared with the vehicle group (i.v. drip of PSS at a rate of 0.3 mL/h) during a 6 h observation period. N-Acetylcysteine, given 10 min prior to LPS, significantly increased the survival rate. 6. The results of the present study suggest that NAC exerts a protective effect on the LPS-induced ALI. The mechanisms of action may be mediated through the reduction of the production of NO, free radicals and pro-inflammatory cytokines.