The mortality cases caused by influenza virus are offen associated with the secondary bacterial infection, Streptococcus pneumoniae infection in particularly. The mechanisms underlying the interaction between the virus and the bacteria are unclear at present. The damage of normal protective epithelial layer and changes in airway function caused by influenza virus provides increased numbers of attachment sites and culture spaces for the bacteria. The effect of influenza on immune system is a further opportunity for subsequent bacterial infection. The synergistic effect between influenza virus and Streptococcus pneumoniae might not be unidirectional. The bacteria caused the secondary infection could enhance the pathogenicity of the virus. The bacterium-derived proteases could cleave hemagglutinin to its active components that are required for infectivity of the virus. The effect of the bacteria on the virus could enhance the lethality of the primary viral disease, which can explain why antibiotic therapy was less successful to treat the influenza patient with subsequent bacteria infection. Effective strategies to prevent and treat the severe diseases could be suggested based on the knowledge of interaction between virus and bacteria.

Objective: To investigate the role and mechanism of Hydroxysafflor yellow A (HSYA) in the calcification of vascular smooth muscle cells (VSMC) induced by β-glycerol phosphate (β-GP). Methods: VSMC were cultured with 10% fetal bovine serum+1% double anti-high glucose DMEM medium at 37℃ and 5%CO₂ incubator, and were subcultured according to cell growth density at 1∶4 ratio. The cells were divided into three groups: control group (NC), high-phosphate-induced calcification (HP) group, and HSYA intervention (HSYA) group. The Calcium deposition amount was measured by alizarin red staining and calcium determination kit. The expressions of ALP, RUNX2, RANKL, α-SMA and inflammation indicators TLR4, TNF-α, IL-8 were detected by Western blotting method; Western blotting was also used to detect calcification index alkaline phosphatase (ALP) and Runt-related transcription factor 2 (RUNX2). Nuclear factor kappa B receptor activating factor ligand(RANKL), α-smooth muscle actin (α-SMA), and the expressions of TLR4/NF-κB pathway and inflammatory response-related indicators Toll-like receptor 4 (TLR4), interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-α). The nuclear protein and cytoplasmic proteins were respectively extracted. The expressions of p65 in nucleus and cytoplasm, as well as the expressions of p65 and phosphorylated p65 in total proteins were detected by Western blotting method. Superoxide dismutase (SOD) and malondialdehyde (MDA) kit were used to detect the content of antioxidant enzymes and oxidation end products in cells. Results: Western blotting showed that the expressions of ALP, RUNX2 and RANKL in HSYA group were significantly lower than that in HP group. The expression of α-SMA was increased than that of HP group (all P<0.01). The expression levels of TLR4, TNF-α, IL-8 and p-NF-κB/p65 in HSYA group were decreased compared with that in the HP group, and p65 was decreased in nucleus and increased in cytoplasm (all P<0.05). SOD content in HSYA group was significantly higher than that in HP group, and MDA content was significantly lower than that in HP group (all P<0.01). Conclusions HSYA can reduce calcification and calcium deposition of vascular smooth muscle cells induced by high phosphorus. The mechanism is related to the inhibition of the activation of TLR4/NF-κB pathway and the inhibition of oxidative stress.