Tapan Bhavsar

Attenuating effect of taurine on lipopolysaccharide-induced acute lung injury in hamsters

This study has evaluated the ability of the semiessential amino acid taurine to attenuate lipopolysaccharide (LPS)-induced lung inflammation, oxidative stress and apoptosis in a small animal model. For this purpose, bacterial LPS (0.02mg in phosphate buffered saline (PBS) pH 7.4) was instilled intratracheally into female Golden Syrian hamsters, before or after a 3-day intraperitoneal treatment with a single dose (50mg/kg in PBS pH 7.4) of taurine. At 24h after the last treatment, lung tissue and bronchoalveolar lavage fluid (BALF) samples were collected. In comparison to samples from animals receiving only PBS pH 7.4, serving as controls, those of LPS-stimulated animals exhibited a higher count of both total leukocytes and neutrophils in the BALF, and increased incidence of apoptosis, depletion of intracellular glutathione and evidence of inflammation confined to the parenchyma in the lung. In addition, LPS caused cells in the BALF to exhibit a higher expression of tumor necrosis factor-1, a higher activity of caspase-3, marked lipid peroxidation, and altered activities of catalase, glutathione peroxidase and superoxide dismutase relative to control samples. In contrast, a treatment with taurine was found to significantly attenuate all of the cellular and biochemical alterations induced by LPS, more so when given before rather than after the endotoxin. The present results suggest that taurine possesses intrinsic antiinflammatory and antioxidant properties that may be of benefit against the deleterious actions of LPS in the lung.

Aerosolized recombinant human lysozyme ameliorates pseudomonas aeruginosa–induced pneumonia in hamsters

ABSTRACT As an alternative to conventional antibiotics, aerosolized recombinant human lysozyme (rhLZ) was used to treat experimentally induced pneumonia. Syrian hamsters were inoculated intratracheally with a nonmucoid strain of Pseudomonas aeruginosa (PA), then exposed to a 1.0%% solution of rhLZ in water for 2 hours per day for 3 consecutive days (controls were treated with aerosolized water alone). Compared to controls, the rhLZ-treated group showed statistically significant reductions in the following parameters: (1) lung histopathological changes, (2) bacterial colony-forming units in whole lung and bronchoalveolar lavage fluid (BALF), (3) total BALF leukocytes, (4) percent BALF neutrophils, and (5) alveolar septal apoptosis. Exposure to aerosolized rhLZ also resulted in a large increase in BALF lysozyme activity. These findings indicate that aerosolized rhLZ may be potentially useful in reducing the level of bacterial colonization and inflammation in the lungs of patients with PA pneumonia.

Protective action of taurine, given as a pretreatment or as a posttreatment, against endotoxin-induced acute lung inflammation in hamsters

To assess the effect of taurine on lipopolysaccharide (LPS)-induced lung inflammation, oxidative stress and apoptosis, female Golden Syrian hamsters were intratracheally instilled with bacterial LPS (0.02 mg in phosphate buffered saline (PBS) pH 7.4), before or after a 3-day intraperitoneal treatment with a single dose of taurine (50 mg/kg/day in PBS pH 7.4), and bronchoalveolar lavage fluid (BALF) and lung tissue samples were collected at 24 hr after the last treatment. In comparison to BALF samples from animals receiving only PBS pH 7.4, and serving as controls, those of LPS-stimulated animals exhibited a higher count of both total leukocytes and neutrophils and increased expression of tumor necrosis factor receptor 1. In comparison to lungs from control animals, those from LPS-treated animals showed increased cellular apoptosis, lipid peroxidation, decreased glutathione levels, altered activities of antioxidant enzymes (catalase, glutathione peroxidase, superoxide dismutase) and focal inflammation confined to the parenchyma. A treatment with taurine was found to significantly attenuate all these alterations, with the protection being, in all instances, greater when given before rather than after LPS. The present results suggest that taurine is endowed with antiinflammatory and antioxidant properties that are protective in the lung against the deleterious actions of Gram negative bacterial endotoxin.

Aerosolized recombinant human lysozyme enhances the bactericidal effect of tobramycin in a hamster model of pseudomonas aeruginosa–induced pneumonia

ABSTRACT Previous studies from this laboratory have shown that aerosolized recombinant human lysozyme (rhLZ) mitigates Pseudomonas aeruginosa (PA)-induced pneumonia. In the current investigation, our laboratory tested the hypothesis that aerosolized rhLZ can potentiate the effects of tobramycin (TBMN), thereby reducing the effective dose of this agent in the treatment of PA-induced pneumonia. Syrian hamsters were instilled intratracheally with PA, then exposed to an aerosol containing either 1% rhLZ, 3 μg TBMN, or a combination of both agents. In contrast to the initial studies with rhLZ, which involved 3 separate aerosol exposures, only a single treatment was used in the current investigation. Twenty-four hours after completion of the aerosol regimen, the following parameters were measured: (1) whole-lung colony-forming units (CFU), (2) total bronchoalveolar lavage fluid (BALF) CFU, (3) lung histopathology, and (4) total BALF neutrophils. The combination of rhLZ and TBMN significantly reduced whole-lung and BALF CFU, as well as the inflammatory index, compared to TBMN alone. Similar results were seen in vitro with regard to bactericidal activity. These findings provide a rationale for clinical testing of rhLZ as an adjunct to commercial antibiotic treatment.

Preferential recruitment of neutrophils by endothelin-1 in acute lung inflammation induced by lipopolysaccharide or cigarette smoke

This study examined the role of endothelin-1 (ET-1) in recruiting inflammatory cells to the lung after induction of injury with either lipopolysaccharide (LPS) or cigarette smoke. Hamsters injected with either ET-1 or its precursor peptide (Big ET-1) prior to treatment with LPS or cigarette smoke had markedly increased concentrations of neutrophils in bronchoalveolar lavage fluid (BALF) despite a reduction in total numbers of BALF leukocytes. Furthermore, the effect of ET-1 on smoke-exposed animals was reversed by addition of an endothelin-A receptor antagonist. These results are consistent with preferential recruitment of neutrophils by ET-1, and suggest that inhibition of this proinflammatory mediator may decrease acute pulmonary inflammation associated with cigarette smoke and other pulmonary toxins.

Endothelin-1 potentiates smoke-induced acute lung inflammation.

The current study examined the role of endothelin-1 (ET-1) in mediating acute lung inflammation induced by short-term cigarette smoke exposure. Hamsters received intraperitoneal injections of ET-1, followed by a 2-hour period of smoke exposure, for 3 consecutive days. The lungs were then evaluated for inflammatory changes, using the following parameters: (1) lung histopathology, (2) neutrophil content of bronchoalveolar lavage fluid (BALF), (3) percent tumor necrosis factor receptor 1 (TNFR1)-labeled BALF macrophages, and (4) alveolar septal cell apoptosis. Results indicate that ET-1 significantly amplified the effect of smoke on each of these inflammatory markers and that these responses could be blocked by pretreatment with a novel endothelin receptor A antagonist, HJP272. In particular, exogenous ET-1 induced a marked increase in BALF neutrophils, consistent with a role for this mediator as an inflammatory cell “gatekeeper.”

Short-Term Cigarette Smoke Exposure Predisposes the Lung to Secondary Injury

Brief exposure to cigarette smoke is not generally associated with pulmonary injury and may adversely affect the lung only if underlying disease is present. To test this hypothesis, our laboratory performed a series of experiments involving exposure of hamsters to second-hand cigarette smoke (2 h/day for 5 days), either immediately before or after induction of acute pulmonary injury by intratracheal administration of amiodarone. Compared to controls receiving amiodarone alone, hamsters pretreated with smoke showed significant increases in the following parameters: (1) lung inflammation graded on a scale of 0-4 (3.4 vs. 1.6; p < 0.001), (2) percentage of neutrophils in bronchoalveolar lavage fluid (BALF) (75.0 vs. 1.3; p < 0.001), (3) percentage of TNFR1-positive BALF macrophages (44.7 vs. 2.7; p < 0.001), and (4) apoptotic lung parenchymal cells per ten high-power microscopic fields (7.3 vs. 0.7; p < 0.001). Animals post-treated with smoke also showed significant increases in these parameters compared to controls but to a lesser degree than pre-exposed animals. With regard to human disease, such synergistic interactions may account for a significant portion of the morbidity associated with second-hand smoke exposure.

PHOSPHORAMIDON, AN ENDOTHELIN-CONVERTING ENZYME INHIBITOR, ATTENUATES LIPOPOLYSACCHARIDE-INDUCED ACUTE LUNG INJURY

Phosphoramidon blocks the formation of endothelin-1 (ET-1), a proinflammatory mediator implicated in the pathogenesis of a variety of lung diseases. To determine whether phosphoramidon can ameliorate pulmonary inflammation, our laboratory undertook a series of experiments involving treatment of hamsters with either intraperitoneal (i.p.) or aerosolized phosphoramidon prior to induction of acute lung injury by intratracheal administration of lipopolysaccharide (LPS). The results indicate that phosphoramidon significantly reduces LPS-induced pulmonary inflammation as measured by lung histology, neutrophil content of bronchoalveolar lavage (BAL) fluid, percent tumor necrosis factor receptor 1 (TNFR1)-labeled BAL macrophages, and alveolar septal cell apoptosis. In additional experiments, i.p. administration of a novel endothelin A receptor anatgonist (HJP272) similarly decreased BAL neutrophils, whereas i.p. administration of either ET-1, or its precursor peptide, “big” ET-1, had the opposite effect. These findings support further evaluation of phosphoramidon and other ET-1 suppressors as potential treatments for human inflammatory lung disease.