RESUMEN
Objective To observe the effects of keratinocyte growth factor-2 (KGF-2) on the expressions of chemokine FKN and tight junction protein claudin-5 in lung tissue of rats with acute lung injury (ALI). Methods Healthy male Sprague-Dawley (SD) rats were randomly divided into normal saline (NS) control group, ALI model group and KGF-2 pretreatment group, with 10 rats in each group. The rat ALI model was reproduced by injection of 0.01 mL/kg oleic acid into the tail vein, and the rats in NS control group were injected with the same amount of NS. The rats in KGF-2 pretreatment group were instilled with 5 mg/kg KGF-2 in the airway at 72 hours before the model reproduction, and the rats in the NS control group and the ALI model group were instilled with the same amount of NS. The abdominal aortic blood of rats was collected at 8 hours after model reproduction, and then the rats were sacrificed, bronchoalveolar in left lung was lavage, and the bronchoalveolar lavage fluid (BALF) was collected for determination of protein levels in plasma and BALF, and the lung permeability index (LPI) was calculated. The lung tissues were harvested, after hematoxylin-eosin (HE) staining, the histopathological changes were observed under light microscope, and the ALI pathology score (LIS) was calculated. The lung wet/dry weight (W/D) ratio was determined. Immunohistochemistry and Western Blot were used to qualitatively and quantitatively analyze the expressions of FKN and claudin-5 in the lung tissue. The correlation between two variables was analyzed by linear or curve fitting correlation analysis. Results In the ALI model group, the lung tissue was severely damaged, and obvious pathological changes were observed, including thickened alveolar space and inflammatory cell infiltration, and LIS score, lung W/D ratio and LPI were significantly higher than those of the NS control group (LIS: 3.56±0.28 vs. 0.62±0.36, lung W/D ratio: 6.37±0.29 vs. 4.39±0.33, LPI: 3.46±0.69 vs. 0.98±0.17, all P < 0.01). Compared with the NS control group, the positive expression of FKN in the lung tissue of the ALI model group was significantly increased, and the expression level was significantly increased (FKN/GAPDH: 0.97±0.18 vs. 0.62±0.04, P < 0.01); the positive expression of claudin-5 was significantly decreased, and the expression level was significantly decreased (claudin-5/GAPDH: 0.56±0.11 vs. 1.06±0.13, P < 0.01). There was a significant negative correlation between FKN and claudin-5 protein expression (r = -0.817, P = 0.025). After pretreatment with KGF-2, the degree of lung tissue damage was significantly reduced, and the pathological changes were significantly improved, and the LIS score, lung W/D ratio and LPI were significantly lower than those of the ALI model group (LIS: 2.41±0.17 vs. 3.56±0.28, lung W/D ratio: 5.45±0.55 vs. 6.37±0.29, LPI: 2.42±0.19 vs. 3.46±0.69, all P < 0.01). Compared with the ALI model group, the positive expression of FKN in the lung tissue of KGF-2 pretreatment group was significantly decreased, and the expression level was significantly decreased (FKN/GAPDH: 0.79±0.03 vs. 0.97±0.18, P < 0.01); the positive expression of claudin-5 was significantly increased, and the expression level was significantly increased (claudin-5/GAPDH: 0.80±0.05 vs. 0.56±0.11, P < 0.01). There was still a significant negative correlation between FKN and claudin-5 protein expression (r = -0.847, P = 0.012). Conclusion KGF-2 may restore the expression of tight junction protein claudin-5 by down-regulating the expression of chemokine FKN, thereby reducing the damage of blood barrier in ALI.
RESUMEN
Increasing evidence suggests that the cerebrospinal fluid-contacting nucleus (CSF-contacting nucleus) mediates the transduction and regulation of pain signals. However, the precise molecular mechanisms remain unclear. Studies show that release of fractalkine (FKN) from neurons plays a critical role in nerve injury-related pain. We tested the hypothesis that release of FKN from the CSF-contacting nucleus regulates neuropathic pain, in a chronic constriction injury rat model. The results show that FKN is expressed by neurons, via expression of its only receptor CX3CR1 in the microglia. The levels of soluble FKN (sFKN) were markedly upregulated along with the increase in FKN mRNA level in rats subjected to chronic constriction injury. In addition, injection of FKN-neutralizing antibody into the lateral ventricle alleviated neuropathic pain-related behavior followed by reduction in microglial activation in the CSF-contacting nucleus. The results indicate that inhibition of FKN release by the CSF-contacting nucleus may ameliorate neuropathic pain clinically.