Development and characterization of a rat model of chronic obstructive pulmonary disease (COPD) induced by sidestream cigarette smoke

Use of a soluble epoxide hydrolase inhibitor in smoke-induced chronic obstructive pulmonary disease

Tobacco smoke-induced chronic obstructive pulmonary disease (COPD) is a prolonged inflammatory condition of the lungs characterized by progressive and largely irreversible airflow limitation attributable to a number of pathologic mechanisms, including bronchitis, bronchiolitis, emphysema, mucus plugging, pulmonary hypertension, and small-airway obstruction. Soluble epoxide hydrolase inhibitors (sEHIs) demonstrated anti-inflammatory properties in a rat model after acute exposure to tobacco smoke. We compared the efficacy of sEHI t-TUCB (trans-4-{4-[3-(4-trifluoromethoxy-phenyl)-ureido]-cyclohexyloxy}-benzoic acid) and the phosphodiesterase-4 (PDE4) inhibitor Rolipram (Biomol International, Enzo Life Sciences, Farmingdale, NY) to reduce lung injury and inflammation after subacute exposure to tobacco smoke over a period of 4 weeks. Pulmonary physiology, bronchoalveolar lavage, cytokine production, and histopathology were analyzed to determine the efficacy of sEHI and Rolipram to ameliorate tobacco smoke-induced inflammation and injury in the spontaneously hypertensive rat. Both t-TUCB and Rolipram inhibited neutrophil elevation in bronchoalveolar lavage. sEHI t-TUCB suppressed IFN-γ, while improving lung function by reducing tobacco smoke-induced total respiratory resistance and tissue damping (small-airway and peripheral tissue resistance). Increases in tobacco smoke-induced alveolar airspace size were attenuated by t-TUCB. Rolipram inhibited the production of airway mucus. Both t-TUCB and Rolipram inhibited vascular remodeling-related growth factor. These findings suggest that sEHI t-TUCB has therapeutic potential for treating COPD by improving lung function and attenuating the lung inflammation and emphysematous changes caused by tobacco smoke. To the best of our knowledge, this is the first report to demonstrate that sEHI exerts significant protective effects after repeated, subacute tobacco smoke-induced lung injury in a rat model of COPD.

Detection of tumor necrosis factor-α and interleukin-6 in exhaled breath condensate of rats with pneumonia due to staphylococcal enterotoxin B

Exhaled breath condensate (EBC) may contain mediators of acute lung injury. The objectives were to determine if EBC could be collected in a mechanically ventilated rat, to measure tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the EBC after staphylococcal enterotoxin B administration (SEB) and to find out if the concentrations of TNF-α and IL-6 correlated with those in lung lavage. Four hours after SEB instillation, rats were placed on mechanical ventilation and EBC was collected over 90 minutes. Lung lavage was collected and white cell count was determined. TNF-α and IL-6 were measured in the EBC and lavage. EBC was available in a sufficient quantity (250-400 μL) for the measurement of cytokines. The rats that received SEB had an inflammatory response when compared to control rats as shown by an increase in white cell count. TNF-α and IL-6 were detected in the EBC. Concentration of TNF-α correlated with that in the lavage (r = .497, P = .021), whereas IL-6 did not. EBC can be collected in rats in sufficient quantities to study acute lung injury. TNF-α and IL-6 can be measured in the EBC. Correlation between TNF-α in the EBC and lavage was demonstrated in this rat model of lung injury.

Patterns of cytokine release and evolution of remote organs from proximal femur fracture in COPD rats

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is at increased risk for developing osteoporosis (OP) with subsequent proximal femur fracture. The presence of COPD is suggested to be a strong risk factor for proximal femur fracture or hip fracture. However, what happen behind it is not clearly understood.

OBJECTIVE

To investigate the pattern of cytokine (TNF-a, IL-6, and IL-10) releases in pulmonary and hepatic in rats with COPD suffering from proximal femur fracture, and its possible adverse effect on pulmonary and hepatic.

METHODS AND SUBJECTIVE

This paper has two parts. In the first part, we describe the procedure of COPD model in detail. In the second part, we study the influences of fracture on the COPD rats. 5 months WISTAR rats with 37 weeks cigarette smoking exposure (CS group) were dynamically determined for pulmonary function, inflammatory response in bronchoalveolar lavage fluid (BALF), histological changes in pulmonary in the first part. When the COPD model is proved to be successful, we begin the second part. COPD rats were euthanized at 2, 24, 48, 72, and 96h after proximal femur fracture (fracture group) or anaesthesia (control group). Cytokines (TNF-a, IL-6, and IL-10) and myeloperoxidase activity of pulmonary and hepatic (MPO) were measured with enzyme-liked immunosorbent assay technique. Permeability changes of the lung were assessed via bronchoalveolar lavage, and those of the liver via assessment of oedema formation. Tissues were further examined microscopically.

RESULTS

The current sidestream cigarette smoke induced rat COPD model has been proved an adequate animal model with several advantages as assessed by dynamically monitored lung mechanics and pathological changes for 37 weeks. In the second part, TNF-a, IL-6, and IL-10 levels of pulmonary tissue were significantly increased after proximal femur fracture compared to control rats. TNF-a, and IL-6 levels in pulmonary peaked at 2h, 24h in fracture group, whereas IL-10 level peaked at 24h and 96h. Pulmonary myeloperoxidase activity, permeability and histological score in fracture group were remarkably elevated, and peaked at 24h. In addition to TNF-a, all above parameters did not return to normal through our study. Hepatic in COPD rats showed notable increase of cytokines (TNF-a, IL-6, and IL-10), myeloperoxidase activity, histological score, and permeability in fracture group compared to control rats, and severity of these changes were much lower than in pulmonary. Apart from TNF-a, the peak of these parameters was at 24h after fracture. Changes of cytokines, MPO activity, permeability and histological score in pulmonary and hepatic in control rat were little changed.

CONCLUSION

COPD rats produced a remarkably increase of inflammatory response (TNF-a, IL-6, IL-10) in lung (liver) after proximal femur fracture, which lead to lung (liver) injury, as evidence by changes of MPO, permeability, and histological scores in local organs.

Carbon monoxide pollution promotes cardiac remodeling and ventricular arrhythmia in healthy rats

RATIONALE

Epidemiologic studies associate atmospheric carbon monoxide (CO) pollution with adverse cardiovascular outcomes and increased cardiac mortality risk. However, there is a lack of data regarding cellular mechanisms in healthy individuals.

OBJECTIVES

To investigate the chronic effects of environmentally relevant CO levels on cardiac function in a well-standardized healthy animal model.

METHODS

Wistar rats were exposed for 4 weeks to filtered air (CO < 1 ppm) or air enriched with CO (30 ppm with five peaks of 100 ppm per 24-h period), consistent with urban pollution. Myocardial function was assessed by echocardiography and analysis of surface ECG and in vitro by measuring the excitation-contraction coupling of single left ventricular cardiomyocytes.

MEASUREMENTS AND MAIN RESULTS

Chronic CO pollution promoted left ventricular interstitial and perivascular fibrosis, with no change in cardiomyocyte size, and had weak, yet significant, effects on in vivo cardiac function. However, both contraction and relaxation of single cardiomyocytes were markedly altered. Several changes occurred, including decreased Ca(2+) transient amplitude and Ca(2+) sensitivity of myofilaments and increased diastolic intracellular Ca(2+) subsequent to decreased SERCA-2a expression and impaired Ca(2+) reuptake. CO pollution increased the number of arrhythmic events. Hyperphosphorylation of Ca(2+)-handling and sarcomeric proteins, and reduced responses to beta-adrenergic challenge were obtained, suggestive of moderate CO-induced hyperadrenergic state.

CONCLUSIONS

Chronic CO exposure promotes a pathological phenotype of cardiomyocytes in the absence of underlying cardiomyopathy. The less severe phenotype in vivo suggests a role for compensatory mechanisms. Arrhythmia propensity may derive from intracellular Ca(2+) overload.