Role Of The Sphk1/S1P Pathway Protects Nonalcoholic Fatty Liver From Ischemia/Reperfusion Injury By Alleviating Oxidative Stress In Hepatocytes

Background and aimsThe incidence of nonalcoholic fatty liver(NAFL)has gradually increased result from the changes in people's living standards and lifestyles,and NAFL has become an exacerbation of hepatic ischemia-reperfusion(I/R)injury in liver surgery,but the pathophysiology of aggravating IRI in the liver remains unclear.Previous studies have particularly highlighted the disorder in sphingolipid metabolism resulting in ceramides(CER)and sphingosine 1-phosphate(S1P)accumulation in the liver with NAFL.Interestingly,the upregulation of CER and S1P were also found in the healthy liver upon I/R challenge.CER is an important component of cell membrane and an important active lipid,which plays an important role in regulating a series of pathophysiological responses such as cell senescence,growth inhibition,apoptosis,and inflammatory response.As a metabolite of CER,S1P is another important active lipid,which plays an important role in regulating cell survival,proliferation and maintaining vascular integrity.CER and S1P are significantly related to the occurrence and development of various diseases.However,there has none of research reported the role of CER and S1P in NAFL upon I/R challenge(NAFL-I/R injury)in mice.This topic will focus on studying the dysfunction of sphingolipid metabolism caused by NAFL-I/R injury,elucidate the mechanism of sphingolipid metabolism dysregulation in the occurrence and development of NAFL-I/R injury,and study the role of sphingomyelin metabolism dysregulation in NAFL aggravating I/R injury.This study will provide a new idea for the clinical prevention and treatment of NAFL-I/R injury.Methods1.Establishment of mouse NAFL model and mouse NAFL-I/R injury model;2.Establish a lipidomics analysis method to study the correlation between NAFL-I/R injury and CER metabolism disorders at the metabolites level;3.Real time PCR detect the mRNA level of CER metabolic enzyme,studying the correlation between NAFL-I/R injury and sphingolipid metabolism at the level of metabolic enzymes;4.Screen and intervene CER metabolic enzymes with significantly different expression levels,and analysis the effects of gene intervention on sphingolipid metabolism and NAFL-I/R injury;5.Exogenous injection of the downstream product of this enzyme to study the effect of this product on NAFL-I/R damage.Results1.Successfully established the mouse NAFL model and mouse NAFL-I/R injury model;2.Revealed lipid metabolism changes in liver after NAFL-I/R injury in mice,and found that I/R activates the sphingolipid metabolism pathway produced by S1P;3.NAFL-I/R injury caused sphingolipid metabolism disorders at the level of metabolic enzymes.Sphk1 is a CER metabolic enzyme with significantly different expression levels in NAFL-I/R injury;4.Knockdown Sphk1 promotes CER production,inhibits S1P production,aggravates oxidative stress in liver cells,causes apoptosis and necrosis,and further aggravates NAFL-I/R injury;5.Exogenous injection of S1P reduce NAFL-1/R injury in mice by inhibiting oxidative stress in hepatocytes.ConclusionsThrough this study,we found that mouse NAFL-I/R injury activates the sphingolipid metabolism pathway of S1P production.Sphk1 is the most significantly altered enzyme in CER metabolic enzymes.Sphk1 maintains S1P production and plays a hepatoprotective role.Sphk1/S1P pathway reduces NAFL-I/R damage in mice by inhibiting oxidative stress in hepatocytes.This study may serve as a clinical target for NAFL-I/R injury in the clinic,which will help develop new therapeutic drugs to treat I/R injury in NAFL patients.