The Prognostic Value Of IL-32 In SCAP And The Protective Effects Of 1,25（OH）₂D₃ On Klebsiella Infection

Objective:Severe community-acquired pneumonia(SCAP)is a common critical illness with high mortality.This study examined the expression of IL-3 2 in plasma of SCAP patients and analyzed its clinical significance.Methods:We Collected 63 cases of venous blood plasma samples from patients with SCAP and 89 blood plasma samples from Non-SCAP patients,In addition,52 healthy volunteers were included as the controls.The end point of the case group was 30 days after diagnosis.Patientrelated clinical information and conduct CURB-65 and PSI scores were collected on the day of diagnosis.We used ELSIA method to detect the expression level of IL-32 in plasma,and analyzed the statistical relationship between IL-32 concentration and clinical variables.ROC curve was used to evaluate the value of each clinical variable in predicting death within 30 days of SCAP patients.Kaplan-Meier method was performed to calculate the effect of different IL-32 expression levels on patient survival.The Cox proportional hazard regression model was applied for analyzing and screening independent risk factors for patient survival.Results:The concentration of IL-32 in plasma of SCAP group was significantly higher than that of Non-SCAP group and healthy control group(P<0.001),There was no significant difference in the expression level of IL-32 between Non-SCAP group and healthy control group(P=0.482).The concentration of IL-32 was not significantly correlated with the age,sex,smoking history and distribution of pathogens in SCAP patients,but positively correlated with CURB-65,PSI scores,and the need for vasopressor or invasive mechanical ventilation in SCAP patients.ROC curve analysis found that the AUC value of IL-32 predicted death in patients with SCAP is 0.793(P<0.001),the optimal cutoff value is IL-32>15.2 pg/mL.The concentration of IL-32 in the survival group of SCAP patients was significantly lower than that in the death group.Kaplan-Meier method confirmed that the 30-day cumulative survival rate of IL-32 high expression group in SCAP patients was significantly lower than that in low expression group(P<0.001).Multivariate Cox regression analysis found that IL-32>15.2 pg/mL and PSI>137 were independent risk factors for survival in SCAP patients.The RR were 2.936(P=0.028)and 6.571(P=0.003),respectively.Conclusion:The plasma concentration of IL-32 is related to the severity and prognosis of patients with SCAP.IL-32 is a potential molecular marker for assessing and judging the prognosis of patients with SCAP.Klebsiella pneumoniae(Kp)is a Gram-negative bacillus an common pathogen for community-acquired pneumonia and nosocomial pneumonia.In recent years,Kp’s resistance to antibiotic has become increasingly serious which leads to a great therapeutic dilemma.Macrophages are the major innate immunocyte.Autophagy plays an important role in the process of macrophage’s clearance of pathogens.Studies have shown that 1,25(OH)2D3 can induce autophagy.However,the role of 1,25(OH)2D3 in the process of macrophage’s clearance of Kp infection and its related mechanisms are still unclear.In this study,We used Kp infected THP-1 derived macrophage and established Kp-infected mouse pneumonia model to investigate the role of 1,25(OH)2D3 in macrophage’s clearance of KP infection.In this study,we found that 1,25(OH)2D3 promotes autophagy in macrophages by activating VDR and upregulating Atg16L1 expression.Thereby enhancing its clearance of Kp infection and declined the expression of various proinflammatory cytokines like TNF-α,IL-6 and IL-1β.These effects of 1,25(OH)2D3 were attenuated by using the autophagy inhibitor bafilomycin as well as knock down the expression of VDR and ATG16L1.The pneumonia model of Kp-infected mice showed that intraperitoneal injection of 1,25(OH)2D3 significantly reduced the infiltration inflammatory cells,lung injury and bacterial burden.The survival time of the mice in the 1,25(OH)2D3 injection group was higher than that in the control group.The protective effect of 1,25(OH)2D3 was significantly attenuated when the autophagy inhibitor chloroquine was used at the same time.In summary,1,25(OH)2D3 up-regulates the expression of Atg16L1 by activating VDR to induce macrophages autophagy,thereby enhancing its ability to alleviate Kp infection,while decreasing the production of various pro-inflammatory cytokines and reducing lung injury.