Hip fracture aggravates systemic inflammation and lung injury in aged chronic cigarette smoke exposed rats

The aim of this investigation was to examine the influence of hip fracture on systemic inflammation and lung injury in aged chronic cigarette smoke exposed rats. Male Sprague Dawley (SD) aged rats (22-25 months old, 460-570 g) were used. Animals were subjected to either chronic cigarette smoke (CS) or air exposure for 12 weeks. These animals then underwent a sham procedure or hip fracture. Endpoint was 24 h. Systemic inflammation was assessed by TNF-α, IL-6, and IL-10 levels. Pulmonary function, inflammatory cell counts and protein concentrations in BAL, pulmonary pathological changes and scores were obtained to assess lung injury. And TLR4 mRNA expression in lung tissue was determined. The indices mentioned above were unchanged in air-exposed rats after hip fracture. However, CS-exposed animals were found to have increased serum levels of TNF-α, IL-6, and IL-10, impaired pulmonary function, increased inflammatory cell counts and protein concentrations in BAL, and intensified pathologic changes and scores. In addition, lung tissue harvested following CS-exposure demonstrated increased TLR4 mRNA expression. Our results indicate that systemic inflammation and lung injury in aged CS-exposed animals were further aggravated by hip fracture. The overexpression of TLR4 mRNA induced by CS exposure may, at least in part, involve in this process.