Inflammatory Stress Disrupt FAT/CD36Expression And Exacerbate Lipid Accumulation And Injury In Kidney

Objectives: Chronic, low grade and systemic inflammation is closelyrelated to lipid metabolism disorders， inflammation involved in theoccurrence and development of metabolism disease through a variety ofcell signal pathway. In the study of the patients who with chronic kidneydisease，we found that inflammatory cytokines level in the serum of thesepatients increased significantly. Our study is to induce inflammatory modelusing casein injection in C57BL/6J mice，mimic human chronic, low gradeand systemic inflammatory state.Methods: Eight week-old male C57BL/6J mice were randomlyassigned to4groups for different diet and treating methods:Normal chow diet group (NCD), NCD plus subcutaneous injection ofcasein group (NCD+Casein), high fat diet group (HFD) and HFD plussubcutaneous injection of casein group (HFD+Casein). High fat dietcontains35%fat,26%protein and0.3%cholesterol. The NCD+casein group and the HFD+casein group mice were treated with casein injectionevery other day, and the other mice were treated with NS injection. Themice were sacrificed after14weeks and the blood was collected for serumamyloid A (SAA), human tumor factor-α（TNF-α）and FAA assays.Collected the renal tissues. The serum SAA, TNF-α and FAA levels weremeasured by ELISA kits.Results: The levels of serum inflammation cytokines (TNF-α, SAA)and serum FFA level were higher in casein-injected mice compared withtheir respective controls.Conclusion: Inflammation can be induced in C57BL/6J mice after thesubcutaneous injection of casein for14weeks．The inflammatory modelhave been established successfully． Objectives: To study the disturbance of lipid metabolism underinflammatory stress by detecting the lipid level in the kidney of C57BL/6Jmice, HMCs and HK2cells, to observe the oxidative stress levels andfibrosis levels in kidney, HMCs and HK2cells. Methods: Human kidney mesangial cells (HMCs)and human kidneyproximal tubular epithelial cells（HK2）were both treated with serum freemedium (control),palmitic acid(PA,0.04μmol/ml),TNF-α(25ng/ml),IL-6(20ng/ml),0.04μmol/ml PA plus25ng/ml TNF-α,0.04μmol/ml PAplus20ng/ml IL-6. The arrangement of C57BL/6J mice was descripted inPart1.The lipid accumulation in renal tissues or in cells were measured byOil Red O staining and a quantitative intracellular triglyceride assay wasperformed using colorimetric method. FFA level in HMCs, HK2cells andkidney of C57BL/6J mice were measured by ELISA kits.Oxidatie stresslevel were evaluated by H2O2and ROS tests. Kidney collagen fibers weremeasured by Masson trichrome and sirius red staining. The levels of α-SMA was measured by immunihistochemistry staining. And Blood sampleswere used for test the serum creatinine(Scr), urea nitrogen(BUN).Results: ORO staining, TG and FFA test results showed thatinflammation can stimulate lipid accumulation in HMCs，HK2cells andrenal tissues of C57BL/6J mice. Further analysis showed inflammatorystress can increase H2O2and ROS levels. In vivo studies, Masson trichromestaining and Sirius Red staining showed inflammatory stress induced bycasein injection increased collagen fibers in kidney tissue. Inflammatorystress increased the expression of α-SMA in renal tissues of C57BL/6Jmice also. And inflammatory stress can induce renal function failurecompared with the NCD group. Conclusion：Inflammation can exacerbate lipid accumulation in HK2cells, HMCs and in the renal tissue of C57BL/6J mice, and inflammatorystress could lead to kidney injure. Objective: FAT/CD36, a transmembrane glycoprotein, which iswidely distributed in various tissues, belongs to the scavenger family andplays an impotent role in the uptake of fatty acid. Our study is to observethe expression of FAT/CD36in vivo and in vitro under inflammatorystress.Methods：The levels of FAT/CD36mRNA and protein were tested byreal-time PCR,Western blotting and immunihistochemistry staining.Results： We find that inflammation can increase the mRNAexpression of FAT/CD36in HMCs,HK2and kidney of C57BL/6J mice,high fat diet in mice and palmitic acid loading in cells can increaseFAT/CD36mRNA expression also, and, in the high fat plus inflammatorystress groups the mRNA expression of FAT/CD36increased more significantly. Westein blotting and immunohistochemical staining resultsalso showed that the level of FAT/CD36proteins have been increasedunder inflammatory stress whether in vivo or in vitro, which wereconsistent with the mRNA results.Conclusion： Inflammatory stress can increase the expression ofFAT/CD36in kidney.