Roles Of Sorcin In Acute Inflammatory Response And The Underlying Molecular Mechanism

Host immune response is the normal physiological response and tightly controlled by negative regulators to avoid excessive immune reactions for homeostasis.Some pathogens,such as Foot-and-Mouth Disease Virus(FMDV),may take advantage of host negative regulating system to evade host defense and establish persistent infection.Our previous report showed that FMDV VP1 interacted with cellular protein soluble resistance-related calcium-binding protein(Sorcin)and Sorcin recruited downstream molecular signal transducer and activator of transcription 3(STAT3)in the negative regulation of TNF-a or SeV induced type I interferon and NF-?B response.This observation suggests that Sorcin might act as an important component of host negative regulating system.However,the exact role of Sorcin in animal model is still unclear.Here we show different acute inflammatory animal models to illustrate the underlying molecular mechanism of Sorcin in vivo.In this study,we found that the level of Sorcin in THP-land Raw264.7 cell lines was no significant change with the treatment of TNF-a,LPS or Poly(I:C)by RT-qPCR.Meanwhile,the level of Sorcin in brain,testicle,kidney,thymus and heart was much higher than that in other tissues and organs.The result validates that the expression of Sorcin is related to specific tissue types.To investigate the role of Sorcin in vivo,we backcrossed Sorcin-deficient mice over ten generations to generate C57BL/6 Sorcin-/-mice or BALB/c Sorcin-/-mice.Furthermore,we cultured the Sorcin+/+ or Sorcin-/-splenocytes with plate-bound anti-CD3 mAb in the presence or absence of anti-CD28 mAb or with ConA only and found that the proliferation of Sorcin-/-splenocytes was remarkably enhanced and produced more IL-2,IL-4,IL-17A and IFN-? but less IL-10.These data suggest that Sorcin is involved in the regulation of splenocytes activation and cytokine expressions in cells.To explore the potential roles of Sorcin in the inflammatory response in vivo,we induced hepatitis with ConA.As a result,Sorcin-/-mice developed severer hepatitis than WT controls,which was characterized by severer focal necrosis,widespread swelling and bleeding in liver and spleen,and higher levels of ALT and AST in serum.The H&E staining showed large amount of inflammatory infiltrates,and hepatocyte death in Sorcin-/-mice liver.In addition,the interaction between Sorcin and STAT3 was confirmed by immunoprecipitation.These results indicate that Sorcin may play an inhibitory role in ConA induced inflammatory response in vivo via STAT3.To further observe the exact impact of Sorcin on the regulation of the septic shock,E.coli/LPS-induced septic shock model was used.We infected the mice with 5×107 CFU E.coli(0119)and found that the Sorcin-/-mice were more susceptible than Sorcin+/+ controls.The death rate of Sorcin+/+ mice was 33%,while 80%of Sorcin-/-mice died 96 h post E.coli infection(p<0.05),indicating that Sorcin-/-mice were more susceptible to E.coli-induced septic shock than that of WT controls.In addition,the Sorcin-/-mice induced higher proinflammatory cytokines level(IL-1,IL-6,IL-12,TNF-a and IL-17A)in the blood and promoted the phagocytosis of macrophages in liver and spleen as well as phosphorylation and nuclear transfer of NF-?B,while reduced the phosphorylation of STAT3 post E.coli induced sepsis shock as compared to that of WT controls.Furthermore,we induced septic shock with LPS,the virulence factor of E.coli.The results were consistent with that of the E.coli infection,which showed that Sorcin-/-mice displayed more susceptible and higher proinflammatory cytokine expressions than Sorcin+/+ controls.These results demonstrate that Sorcin negatively regulates NF-?B signaling transduction,inhibiting the proinflammatory cytokine response and suppressing cytokine storm in E.coli/LPS induced septic shock.In summary,our data indicates that Sorcin acts as an important negative regulator to avoid uncontrolled immune response in ConA-induced hepatitis and E.coli/LPS-induced septic shock.These results further our understanding and provide new insights into the molecular mechanisms of Sorcin in immune responses.