Members of the tripartite motif (TRIM) family are a part of the innate immune system to counter intracellular pathogens. TRIM22 has been reported to possess antiretroviral activity. Here we report that TRIM22 is involved in antiviral immunity against hepatitis B virus (HBV). Our results showed that TRIM22, being a strongly induced gene by interferons in human hepatoma HepG2 cells, could inhibit HBV gene expression and replication in a cell culture system as well as in a mouse model system. Importantly, it was found that TRIM22 could inhibit the activity of HBV core promoter (CP) in a dose-dependent manner. However, TRIM22 lacking the C terminal SPRY domain lost this activity. Further study showed that the SPRY domain deletion mutant was localized exclusively to the cytoplasm of HepG2 cells. In contrast, the wild-type TRIM22 was localized to the nucleus, as expected for a transcriptional suppressor. Interestingly, although RING domain mutants of TRIM22 were localized to the nucleus, they could not inhibit HBV CP activity, indicating that TRIM22-mediated anti-HBV activity was dependent on the nuclear-located RING domain. Conclusion: These findings suggest that TRIM22, which exhibits anti-HBV activity by acting as a transcriptional suppressor, may play an important role in the clearance of HBV. (HEPATOLOGY 2009.)

Rational: Myocardial infiltrating macrophages play an important role in the pathogenesis of viral myocarditis in male BALB/c mice following coxsackievirus B3 (CVB3) infection. Interestingly, comparable macrophage numbers were observed in the myocardium of female mice during acute myocarditis. Objective: Given CVB3 infection causes severe myocarditis in male but not female mice, we postulated that macrophages infiltrating the myocardium of female mice may display distinct functional properties that contribute to differential susceptibility to CVB3 myocarditis. Methods and Results: Here, we found that myocardial infiltrating macrophages from CVB3-infected male mice expressed high levels of classically activated macrophages (M1) markers, including inducible nitric oxide synthase, interleukin-12, tumor necrosis factor-α, and CD16/32, whereas those of females showed enhanced expression of arginase 1, interleukin-10, macrophage mannose receptor (MMR) and macrophage galactose type C-type lectin (MGL) that were associated with alternatively activated macrophage (M2) phenotype. Moreover, distinct myocardial-derived cytokines were found to play a critical role in differential macrophage polarization between sexes after CVB3 infection. Adoptive transfer of ex vivo programmed M1 macrophages, as expectedly, significantly increased myocarditis in both male and female mice. Strikingly, transfer of M2 macrophages into susceptible male mice remarkably alleviated myocardial inflammation by modulating local cytokine profile and promoting peripheral regulatory T cell (Treg) differentiation. Conclusions: Taken together, this study may facilitate the understanding of the mechanism underlying gender bias in susceptibility to CVB3 myocarditis and the development of therapeutic strategies based on macrophage polarization for inflammatory heart disease.

Patients with systemic lupus erythematosus (SLE) are found to be accompanied with innate immunity dysregulation including abnormally macrophage activation. But the functional polarization of the activated macrophages and its underlying molecular mechanism during the pathogenesis of SLE remains unknown. As an important local cellular interaction mechanism responsible for cell fate determination, Notch signaling is reported to exert crucial functions in the development and differentiation of various immunocytes, whereas its role in macrophage polarization is not fully understood. In this study, in the SLE murine model generated by immunization with activated lymphocyte-derived DNA (ALD-DNA), infiltrated macrophages in the nephritic tissues were found to exhibit activation and M2b functional polarization. Notch1 signaling activity was significantly upregulated in the ALD-DNA–induced M2b macrophages in vitro and in vivo. Furthermore, ALD-DNA–induced M2b polarization was found to be dependent on enhanced Notch1 signaling through accelerating NF-κB p50 translocation into the nucleus mediated by PI3K and MAPK pathways. Moreover, blockade of Notch1 signaling with γ-secretase inhibitor treatment before or after the disease initiation could ameliorate murine lupus through impeding macrophage M2b polarization. Our results implied that Notch1 signaling-dependent macrophage M2b polarization might play a pivotal role in the pathogenesis of SLE, which could provide Notch1 signaling blockade as a potential therapeutic approach for SLE disease.

Viral myocarditis, which is most prevalently caused by coxsackievirus B3 (CVB3) infection, is a serious clinical condition characterized by cardiac inflammation. Inflammasome plays an essential role in the regulation of diverse inflammatory responses by serving as a platform for caspase-1 activation and caspase-1-dependent proteolytic maturation and secretion of IL-1β. Although inflammasome has been reported to be crucial for the development of many inflammatory diseases, its role in the pathogenesis of viral myocarditis is still elusive. The present study aims to investigate whether CVB3 infection activates inflammasome and whether the activation of inflammasome contributes to CVB3-induced myocarditis. Our results showed that CVB3 infection induced inflammasome activation both in vitro and in vivo. With the inhibition of inflammasome activation, the severity of CVB3-induced myocarditis was significantly alleviated as evidenced by less weight loss, decreased serological indexes of creatine kinase and creatinekinase-MB activities, as well as less severe myocardial injury. Of importance, echocardiography results showed that inhibition of inflammasome activation also efficiently improved cardiac function as revealed by enhanced left ventricular ejection fraction and left ventricular fractional shortening. Despite that CVB3 infection significantly increased the expression of both retinoic acid-inducible gene 1 and NOD-like receptor family, pyrin domain containing 3 (NLRP3) in cardiac myocytes, CVB3-induced inflammasome activation was NLRP3-, but not retinoic acid-inducible gene 1, dependent. Further study showed that reactive oxygen species production and K⁺efflux were critical for the activation of NLRP3 inflammasome upon CVB3 infection. Collectively, our study demonstrated a crucial role of the NLRP3 inflammasome in the pathogenesis of CVB3-induced myocarditis, and modulation of inflammasome activation might represent a promising therapeutic strategy for viral myocarditis.