br Material and methods br Results br

Material and methods
Results
Discussion RSV is a major cause of lower respiratory tract infections in infancy and early childhood. Several observations suggest that immunological mechanisms may be the key to understand the severity of RSV bronchiolitis in infancy. Several laboratories have demonstrated that RSV induced cytokines such as TNF-alpha and IL8 and chemokines such as CCL5 and CCL3 release from immune and epithelial Apatinib receptor of the human lower respiratory tract and play a fundamental role in the pathogenesis of RSV-induced disease [7], [15]. A positive correlation between nasopharyngeal CCL3 and CCL5 [16] concentrations and illness severity was shown in evaluating patients with RSV bronchiolitis [17]. CCL5 and CCL3 are important for monocyte and lymphocyte recruitment to the lung during RSV infection [7], [16], [18]. Despite the significant progress in the field of RSV immune pathogenesis, however, still unanswered questions regarding the exact mechanism of this process remains to be elucidated. To examine the relationship between 12/15 LOX expression, chemokine production and inflammatory cell infiltration, evaluations were performed at day 5 after RSV infection. BAL cellularity was significantly enhanced at day 5 after RSV infection compared to basal levels (Fig. 1A and B). With respect to cytokine enhancement in lung and BAL cells, the levels of CCL3 and CCL5 were enhanced compared with control group day 5 after RSV infection (Fig. 3, Fig. 4). To investigate potential tissue-specific roles of 12/15-LOX in RSV infection, we surveyed 12/15-LOX mRNA expression in both lung and BAL mice using real-time RTPCR. The mRNA expression level was significantly higher in BAL cells compare to the lung tissue. It was also previously shown that 12/15-LOX mRNA in elicited peritoneal macrophages was 1000 times higher than that in other tissues, including lung, heart, atherosclerotic vessel, liver, gut, spleen, lymph node, kidney, and adipose tissue [12]. In this study, we have founded a potential link between the 12/15-LOX expression and the expression of important pro-inflammatory chemokines in RSV infection. The significantly higher expression of 12/15-LOX during acute RSV infection as well as CCL3 and CCL5 indicates that the elevated classical chemokines levels may due to elevated levels of 12/15-LOX. These results suggest that infiltrating immune cells specially monocytes and neutrophils may be the main source of 12/15-LOX and possibly of some chemokines in vivo. Consistent with our results, it was shown that CCL5 was deficient in the absence of 12/15-LOX during acute bacterial inflammation in mice model [19]. 12/15-LOX pathway induces inflammation in a variety of tissues. In an experimental mice model, pharmacological inhibition of 12/15-LOX significantly decreased neutrophil accumulation in the intravascular, interstitial and alveolar compartments, decreased pulmonary edema formation and decreased the histological signs of lung injury compared to control mice [9]. It was also suggested that 12/15-LOX is critically involved in the regulation of neutrophil recruitment into the different compartments of the lung by modulating chemokine/chemokine receptor homeostasis in LPS-induced pulmonary inflammation [9]. The main pro-inflammatory product of 12/15-LOX is 12-HETE [9]. 12-HETE has been recognized as an inflammatory compound [20], [21], [22]. It has a variety of biological functions. It is a potent, pro-inflammatory chemoattractant for neutrophils [9]. A recently published study demonstrated that 12/15-LOX-derived 12-HETE regulates vascular permeability in acute lung injury through a CXCR2-dependent mechanism and blocking of 12/15-LOX has been proposed as a possible anti-inflammatory approach for therapy. Given these findings, further experiments included evaluation of induced 12(S)-HETE, 2–5 days after the RSV infection in BALF and its relation with immune cell infiltration should be evaluated. Also blocking or eliminating 12/15-LOX or 12(S)-HETE in RSV infection may reduce neutrophil recruitment and could lead to a survival benefit in RSV-induced airway inflammation.