Hypoxia-induced acute lung injury is aggravated in streptozotocin diabetic mice

Hypoxia is an inevitable consequence of many respiratory diseases resulting from inadequate alveolar ventilation. As pulmonary dysfunction is recently recognized as one of the many clinical features associated with diabetes, this study aims to investigate the effect of streptozotocin (STZ)-induced diabetes on hypoxia-induced lung injury.

Mice were randomly allocated to four groups (Control, Hypoxia, Diabetes, Diabetes+Hypoxia). Control and type I diabetic (100 mg/kg STZ-treated) mice were followed for 4 weeks and finally exposed to normoxia or hypoxia (8% O2). Twelve hours later, lung tissues were collected for histopathologic examination, and determination of interleukin (IL)-1β, IL-6, myeloperoxidase (MPO), malondialdehyde (MDA), total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, and Toll-like receptor (TLR)4 expression.

STZ-induced diabetes aggravated histopathological changes in the lung exposed to acute hypoxia. Hypoxia increased lung MDA level but decreased T-AOC and SOD activity. STZ-induced diabetic mice presented significant increases in MDA level and SOD activity in the lung. Moreover, no difference was found in the levels of both oxidant index (MDA) and anti-oxidant indexes (T-AOC and SOD) between "Hypoxia" group and "Hypoxia plus Diabetes" group. On the other hand, STZ-induced diabetic mice presented significant increases in pulmonary neutrophil infiltration, pro-inflammatory cytokines (IL-1β and IL-6) production, as well as TLR4 expression. Although acute hypoxia alone had no significant effect on pulmonary inflammatory markers, it profoundly increased STZ-diabetes-induced neutrophil infiltration, pro-inflammatory cytokine production, and TLR4 expression in lung tissues.

STZ-induced diabetes may aggravate acute hypoxia-induced lung injury through enhancing pulmonary inflammatory responses.