Ificant effect on this proliferation index. Control includes both sham and right lungs (3? rats/group, **P,0.01 vs control). doi:10.1371/journal.pone.0066432.gAcute Ischemia and CXC ChemokinesFigure 8. Functional angiogenesis assessed by Title Loaded From File fluorescent microsphere infusion 14 d after LPAL Dexamethasone treatment had no significant effect on the magnitude of bronchial angiogenesis (n = 4?/group). doi:10.1371/journal.pone.0066432.g[12]. This observation suggests that BAL fluid may not fully reflect lung parenchymal changes. In an attempt to examine more specifically the niche where bronchial vessels originate, we also studied the tissue comprising the left mainstem bronchus. We evaluated CXCL1 and CXCL2 cytokine messenger RNA and protein expression within the bronchial tissue. Results showed that both CXCL1 and CXCL2 protein expression was increased by 6 h after the onset of ischemia. However, since we saw that the right bronchus also showed increased CXCL1 gene expression, we suggest that this is a more generalized response to surgery and or anesthesia. Interestingly, CXCL2 and its primary receptor CXCR2 were uniquely expressed only in the left bronchus, the site of subsequent arteriogenesis. This observation suggests that CXCL2 secretion by local cells within the left bronchus could serve a paracrine role and initiate the growth cascade. Immunostaining for CXCL2 demonstrated that epithelial cells are a likely source of chemokine contributing to the measured changes. However, the contribution of local inflammatory cells, specifically macrophages and neutrophils, requires further evaluation. How pulmonary ischemia stimulates the up-regulation of CXCL2 within large airways is still mechanistically unknown. Given the increase observed in CXCL2 and its epithelial cell source, it is unclear why an increase in this chemokine was not seen in the BAL fluid. This apparent inconsistency might suggest the existence of a positive feedback among members of the CXC family. For example, Zhang and colleagues showed different compartmentalization of CXCL1 and CXCL2 in a rat model of intratracheal LPS challenge [33]. Their results implied that individual CXC chemokines are specifically regulated and may have different effects in the alveolar space and bronchial tissue. Moreover, Zamjahn and coworkers have shown that CXCL1 clearance rate from plasma and blood was more than sevenfold and fourfold higher, respectively, than CXCL2. This indicates the presence of a different flux of CXCL1 and CXCL2 across the epithelial/endothelial barrier of the lung, despite similar molecular size [34]. Cai and colleagues showed that CXCL1 can be important for the local expression of CXCL2 and other cytokines such as CXCL5 [35]. These data add other members of the CXC Ransferred to Hybond N+ membrane (GE Healthcare) overnight. DNA probes for family to a complex scenario. Additional complexity is added when considering receptor affinities as CXCL2 was shown to have a 72-fold greater affinity for CXCR2 than CXCL1 [36?38]. Our results demonstrate unique up-regulation of CXCL2 andits predominant receptor CXCR2 in the left bronchus adding further support that this cytokine-receptor pair are important in airway remodeling. Finally, we delivered an anti-inflammatory treatment to reduce the initial inflammatory response, in an attempt to link an attenuation in chemokine expression with the angiogenic response. Systemic inflammation has been shown to be effectively reduced by the glucocorticoid dexamethasone. Specifically, Sevaljevic and coworkers have demonst.Ificant effect on this proliferation index. Control includes both sham and right lungs (3? rats/group, **P,0.01 vs control). doi:10.1371/journal.pone.0066432.gAcute Ischemia and CXC ChemokinesFigure 8. Functional angiogenesis assessed by fluorescent microsphere infusion 14 d after LPAL Dexamethasone treatment had no significant effect on the magnitude of bronchial angiogenesis (n = 4?/group). doi:10.1371/journal.pone.0066432.g[12]. This observation suggests that BAL fluid may not fully reflect lung parenchymal changes. In an attempt to examine more specifically the niche where bronchial vessels originate, we also studied the tissue comprising the left mainstem bronchus. We evaluated CXCL1 and CXCL2 cytokine messenger RNA and protein expression within the bronchial tissue. Results showed that both CXCL1 and CXCL2 protein expression was increased by 6 h after the onset of ischemia. However, since we saw that the right bronchus also showed increased CXCL1 gene expression, we suggest that this is a more generalized response to surgery and or anesthesia. Interestingly, CXCL2 and its primary receptor CXCR2 were uniquely expressed only in the left bronchus, the site of subsequent arteriogenesis. This observation suggests that CXCL2 secretion by local cells within the left bronchus could serve a paracrine role and initiate the growth cascade. Immunostaining for CXCL2 demonstrated that epithelial cells are a likely source of chemokine contributing to the measured changes. However, the contribution of local inflammatory cells, specifically macrophages and neutrophils, requires further evaluation. How pulmonary ischemia stimulates the up-regulation of CXCL2 within large airways is still mechanistically unknown. Given the increase observed in CXCL2 and its epithelial cell source, it is unclear why an increase in this chemokine was not seen in the BAL fluid. This apparent inconsistency might suggest the existence of a positive feedback among members of the CXC family. For example, Zhang and colleagues showed different compartmentalization of CXCL1 and CXCL2 in a rat model of intratracheal LPS challenge [33]. Their results implied that individual CXC chemokines are specifically regulated and may have different effects in the alveolar space and bronchial tissue. Moreover, Zamjahn and coworkers have shown that CXCL1 clearance rate from plasma and blood was more than sevenfold and fourfold higher, respectively, than CXCL2. This indicates the presence of a different flux of CXCL1 and CXCL2 across the epithelial/endothelial barrier of the lung, despite similar molecular size [34]. Cai and colleagues showed that CXCL1 can be important for the local expression of CXCL2 and other cytokines such as CXCL5 [35]. These data add other members of the CXC family to a complex scenario. Additional complexity is added when considering receptor affinities as CXCL2 was shown to have a 72-fold greater affinity for CXCR2 than CXCL1 [36?38]. Our results demonstrate unique up-regulation of CXCL2 andits predominant receptor CXCR2 in the left bronchus adding further support that this cytokine-receptor pair are important in airway remodeling. Finally, we delivered an anti-inflammatory treatment to reduce the initial inflammatory response, in an attempt to link an attenuation in chemokine expression with the angiogenic response. Systemic inflammation has been shown to be effectively reduced by the glucocorticoid dexamethasone. Specifically, Sevaljevic and coworkers have demonst.
