Molecular Mechanism Of Vascular Leakage Induced By Dengue Virus

Dengue virus?DV?is a single-strand,positive-sense RNA virus belonging to the flavivirus genus of the Flaviviridae family.Dengue is a mosquito-borne infection caused by five serotypes of dengue virus?DV1-DV5?and is prevalent in over 100 tropical and sub-tropical countries with approximately 2.5 billion people at risk.DV infection induces a spectrum of clinical symptoms ranging from classical dengue fever?DF?to severe dengue hemorrhagic fever?DHF?/dengue shock syndrome?DSS?.Clinical manifestation of DF is fever,headache,rash,arthralgia,myalgia and retro-orbital pain and is provided lifelong immunity to the infecting strain.However,secondary infection with different serotypes induces severe DHF/DSS,which is associated with life-threatening increases in hypotension,hypovolemia,vascular permeability and shock.Although a hypothesis is known as antibody-dependent enhancement,the pathogenesis of DHF/DSS remains unclear.Clinical studies demonstrated that cytokines play a vital role in the DHF pathogenesis.During the process of DV infection,cytokines participate in the disease onset and homeostatic regulation.Interleukin-1??IL-1??,is a most important proinflammatory cytokine increased during dengue virus infection.NLRP3inflammasome plays an important role in host natural immune system recognition of pathogen invasion,especially RNA virus infection.In the present study,we revealed a new mechanism by which NLRP3 detects DENV infection thus facilitates the assembly of the NLRP3 inflammasome.It also innovatively linked NLRP3 inflammasome directly to vascular leakage symptoms caused by dengue virus infection.Firstly,we showed that DENV induces the cleavage of pro-caspase-1 and the secretion of mature IL-1?through activating NLRP3 inflammasome.Detailed studies demonstrated that the replication and protein synthesis of Dengue virus is essential for the activation of the NLRP3 inflammasome.More interesting,we found that M protein of Dengue virus promotes the activation of NLRP3 inflammasome through directed interaction with NLRP3.Furthermore,our dates indicated that DENV M protein promotes vascular permeability of organs in Mice through up-regulating the production of IL-1?.However,when we infected NLRP3^-/-mice with AAV9-M,compared with normal mice infected with AAV9-M,the level of IL-1?in organs was significantly decreased and the vascular permeability of organs was significantly restored.Finally,we directly stimulated normal mice with recombinant IL-1?protein and found significantly changes in the vascular permeability of organs.The above experiments indicated that IL-1?that was produced by the NLRP3 inflammasome activated by dengue virus M protein played a direct role in inducing vascular leakage.The NS1 protein of dengue virus could directly induce vascular endothelial cell permeability and lead to vascular leakage.Previous studies have found that NS1,on the one hand,could act as PAMP by releasing inflammatory cytokines through TLR4 to damage the integrity of endothelial cells leading to vascular leakage,on the other hand,NS1 could cause changes in vascular permeability by destroying the polyglycoprotein complex on the cell surface.Since the NS1 protein itself does not have this destructive effect,the specific molecular mechanism is not clear.Here we reveal that DENV induces the secretion of MMP-9 protein in macrophages and PBMCs.Immunoprecipitation screening found that NS1 protein could interact with MMP-9 and NS1 protein promote the secretion of MMP-9 by activating the NF-?B signaling pathway.Further studies have found that NS1 protein could recruit MMP-9 protein from immune cells to endothelial cells,by destroying the junctions between endothelial cells,which leads to the change of endothelial permeability and vascular leakage in MMP-9^-/-mice.Taken together,this work reveals a new mechanism of vascular leakage induced by dengue virus infection.Taking together,our study elucidated the specific molecular of vascular leakage induced by dengue virus infection through different directions,which perhaps provide new insight into the development of therapeutics against DHF/DHS.