Effects Of Vitamin D Supplementation On H9N2 Influenza A Virus-induced Acute Lung Injury In Mice

Acute lung injury is an acute, persistent pulmonary inflammatory response syndrome. In influenza virus infection, overwhelming and simultaneous pro-inflammatory cytokines expression in the lungs are associated with the severe lung damage. To alleviate the lung injury caused by influenza virus, it is crucial to suppress hyper-inflammatory response. As an immunomodulator, vitamin D have been found to influence the production of pro-inflammatory cytokines. Recently, the relationship between vitamin D and influenza virus has become the research hot spot. However, most of current researches are based on designing clinical trials to evaluate the relation between vitamin D and epidemic influenza, it remains unclear whether treatment of vitamin D might alleviate lung injury caused by of influenza viral infection. Therefore, in this study we constructed an ALI mouse model induced by the influenza H9N2 virus, and then elaborated the effect of vitamin D on ALI.Firstly, mice were inoculated intranasally with H9N2 influenza virus to establish ALI mouse model, then daily inoculated intraperitoneally with vitamin D3 on days 1 to 15 post infection. The mice’ clinical signs were monitored daily, and lung injury was evaluated by observation of lung water content and histopathology. Viral titers, cytokines level in lung, and vitamin D content in serum were also measured.More severe clinical signs with notable weight declination, and more sever lung injury were detected in vitamin D-treated infected mice. Furthermore, the mice lung virus titer and the levels of cytokines in lung and the serum concentration of 25-hydroxy vitamin D3 were also increased in vitamin D-treated infected mice.These results demonstrated that supplementation of vitamin D after influenza virus infection had no effect on the inhibition of the H9N2 viral infection, but rather promoted the development of inflammatory responses and caused more severity of ALI in mice. People should be more reasonable on using vitamin D supplement, especially when they get a cold.