Chronic inhalation of H2S in low concentration induces immunotoxicity and inflammatory effects in lung tissue of rats.

Hydrogen sulfide (H2S) is a typical odour compound mainly causing respiratory and central nervous system symptoms. However, the immunotoxicity of inhaled H2S and the underlying mechanisms remain largely unknown. In this study, a low-dose inhalation exposure to H2S was arranged to observe inflammatory response and immunotoxicity in lung tissue of rats. Low concentrations of H2S exposure affected the immune level of pulmonary tissue and peripheral blood. Significant pathological changes in lung tissue in the exposure group were observed. At low concentration, H2S not only induced the upregulation of AQP-4 and MMP-9 expression but also stimulated immune responses, initiating various anti-inflammatory and inflammatory factors, altering tissue homeostatic environments. The TNF and chemokine signaling pathway played an important role which can promote the deterioration of pulmonary inflammatory processes and lead to lung injury and fibrosis. Excessive immune response causes an inflammatory effect and blood-gas barrier damage. These data will be of value in evaluating future occupational health risks and providing technical support for the further development of reliable, sensitive, and easy-to-use screening indicators of exposure injury.

An in vitro rat diaphragmatic fatigue model induced by combined hypoxic and hypercapnic acidosis and the effect of salmeterol.

Hypoxia or hypercapnia impairs diaphragmatic contractility and induces fatigue. However, little is known about the combined effect of hypoxic and hypercapnic acidosis (HHA) on diaphragmatic fatigue. In this study, a gas mixture (21% O2, 12% CO2 and 67% N2) was used to produce HHA-induced rat diaphragmatic fatigue. Force-frequency relationships and twitch characteristics including peak twitch tension (PTT), time to peak tension (TPT), half relaxation time (1/2RT), maintaining tension (MT) and direct-muscle-stimulation tension (MST) were measured in diaphragm preparations from male SD rats. The HHA gas mixture attenuated force at all frequencies (5-120 Hz) and decreased PTT, MT and MST significantly. Aminophylline, a positive control drug, blocked the negative inotropic effect of HHA in a dose-dependent manner. Moreover, salmeterol, a long-acting beta2-adrenoceptor agonist, inhibited the harmful effect of HHA at high frequencies (40-120 Hz), but without effect on MT and MST. These results suggest that an in vitro HHA-induced rat diaphragmatic fatigue model could be established by aerating with the gas mixture, which may be an optimal model to screen effective drugs for diaphragmatic fatigue. Furthermore, salmeterol may play a protective role in HHA-induced impairment.

[A model for quantitative cigarette smoking and response of airways to cigarette smoke in guinea pigs].

OBJECTIVE: To establish an animal model for quantitative cigarette smoking and to determine the acute response of airways to cigarette smoke in guinea pigs. METHODS: The device for inhaling quantitative cigarette smoking was made, which was double pass and single-direction with the minimum dead space. The changes of airway resistance(R(L))and dynamic lung compliance(Cdyn) in guinea pigs exposed to compound air consisting of 75% cigarette smoke and 25% oxygen were observed. Exudation of Evans blue in pulmonary vessels was also determined after consecutive inhalation of 60 ml smoke. RESULT: The R(L) increased from the baseline of (0.21+/-0.05) cmH(2)O x ml(-1) x s to (0.37+/-0.13) cmH(2)O x ml(-1) x s after 10 consecutive breaths of cigarette smoke exposure(P<0.01). The Cdyn decreased to (61+/-19)% of baseline at the ninth to eleventh breaths (P<0.01). The exudations of Evans blue significantly increased in all measured parts of the airways such as lower trachea, main bronchi, proximal intrapulmonary airways and distal intrapulmonary airways (P<0.01). CONCLUSION: The model established in this study is useful for measuring the acute responses of airways induced by cigarette smoke in guinea pigs. Acute inhalation of cigarette smoke decreases dynamic lung compliance, increases airway resistance and vascular permeability of pulmonary vessels in guinea pigs.