Secondary methicillin‐resistant Staphylococcus aureus (MRSA) infection is a cause of severe pneumonia with high mortality during influenza A virus (IAV) pandemics. Alveolar macrophages (AMs) mount cellular defenses against IAV and MRSA infection, which occurs via the nucleotide‐binding domain‐like receptor protein 3 (NLRP3) inflammasome. However, the activity and function of the NLRP3 inflammasome in MRSA pneumonia secondary to IAV infection remain unclear. To clarify this, we studied MRSA infection secondary to IAV both in vitro and in mouse model. The expression of the NLRP3 inflammasome was evaluated by quantitative reverse transcription polymerase chain reaction, immunofluorescence, Western blot, and enzyme‐linked immunosorbent assay. The lung pathology and the rate of weight change were observed. We found that IAV infection for 1 week activated NLRP3 inflammasome. The enhanced expression of NLRP3, caspase‐1, and cleaved caspase‐1 was associated with MRSA infection secondary to IAV, but the expression of interleukin (IL)‐1β decreased in superinfection with MRSA both in vitro and in vivo. The aggravated inflammatory pathology in MRSA pneumonia secondary to IAV infection was associated with decreased expression of IL‐1β. And increased weight loss in MRSA pneumonia secondary to IAV infection was related to decreased concentration of IL‐1β in serum. It infers that superinfection with MRSA reduces expression of IL‐1β someway, and decreased expression of IL‐1β impairs the host immunity and leads to aggravated pneumonia. These results contributed to our understanding of the detailed activity of the NLRP3 inflammasome, IL‐1β, and their relationship with aggravation of MRSA pneumonia secondary to IAV infection. Immunotherapy targeting the IL‐1β signaling pathway could be possible therapeutic strategy for secondary MRSA pneumonia.

The fruit of Xanthium strumarium L. (Asteraceae) has been used for the treatment of various inflammatory diseases. This study investigates the protective effect of caffeoylxanthiazonoside (CYXD) isolated from fruits of X. strumarium on sepsis mice in vitro and in vivo. Cecal ligation and puncture (CLP) operation was used to establish the sepsis mice model, and sham mice were also performed. CYXD was administered by intraperitoneal injection (10, 20, and 40 mg/kg/d), then the survival rate was measured in 96 h. Additionally, sepsis mice were induced by injection LPS (2 mg/kg); CYXD was administered by intraperitoneal injection (10, 20, and 40 mg/kg/d), then mice were sacrificed, and serum levels of TNF-α and IL-6 were determined by ELISA assay. Furthermore, the ability of CYXD to neutralize LPS was measured by using the LAL test, and expressions of TNF-α, IL-6 were determined by using real-time fluorogenic PCR. Results indicated that CYXD significantly elevated survival rates of sepsis mice induced by CLP (p < 0.05) with survival rates of 35%, 45%, and 65%. Furthermore, the LPS level was decreased obviously by CYXD (1, 2, and 4 mg/L) (p < 0.05). Additionally, CYXD (10, 20, and 40 mg/kg) can not only significantly decrease TNF-α and IL-6 levels induced by LPS in mice's serum (p < 0.05), but also inhibit mRNA expressions of TNF-α and IL-6 induced by LPS in RAW 264.7 cells at doses of 20, 40, and 80 μg/mL (p < 0.05). Our study demonstrated that CYXD has significant protective effects on sepsis mice.

Aim: The aim of this study was to investigate the activity of NLRP3 inflammasome and its effect on inducing severe pneumonia 1 week after influenza A virus (IAV) infection. Materials & methods: The expression levels of NLRP3, caspase-1 and IL-1β were assessed in murine macrophages stimulated with IAV. And the severity of viral pneumonia in mice was explored. Results & conclusion: The data showed that although the expression of NLRP3 diverged, activity of NLRP3 inflammasome was enhanced 1 week after IAV infection, and more severe viral pneumonia was associated with IL-1β in serum. It infers that enhanced activity of NLRP3 inflammasome induces augmented expression of IL-1β and severe pneumonia in a NLRP3-independent way, 1 week after IAV infection.

Background and Aims: Influenza A virus (IAV) is the major cause of severe viral pneumonia. The NLRP3 inflammasome in macrophages has been found essential for responsing against IAV infection. The pathology and immunity in IAV infection are self-limited to within one week commonly. Meanwhile, researches found that inflammation induced by NLRP3 inflammasome in the early and later stage of IAV infection was under debate. This study aims to investigate the detailed activity and role of NLRP3 inflammasome during IAV infection in vitro. Methods: After mouse macrophages were cultured and infected with IAV H1N1 for 6 hours (6h group) and one week (1w group) respectively, RT-qPCR was applied to detect the transcription of NLRP3, caspase-1 and IL-1β, western blot was used to detect the protein of NLRP3, caspase-1 and cleaved caspase-1, protein of NLRP3 in cells was also observed by immunofluorescent staining, and the concentration of IL-1β in supernatant was measured by ELISA. Results: In 6h group, the expression of NLRP3, caspase-1, cleaved caspase-1, IL-1β were increased compared with those of blank group (all P<0.05). The data showed the expression of NLRP3, caspase-1 and IL-1β diverged in IAV infected macrophages at one week after infection. In 1w group, expression of NLRP3 decreased, while expression of caspase-1, cleaved caspase-1 and IL-1β increased sequentially, compared with 6h group (all P<0.05). Conclusion: These findings confirmed that IAV infection activated NLRP3 inflammasome, and the divergent expression of NLRP3 from caspase-1 and IL-1β in 1w group suggested that the transcription and secretion of IL-1β was independent of NLRP3 in the later stage of IAV infection.

Background and Aims: Secondary methicillin resistant staphylococcus aureus (MRSA) infection enhances severity of viral pneumonia with high mortality during influenza A virus (IAV) pandemics. There were abundant researches found that NLRP3 inflammasome in macrophages played an important role in mediating inflammation and immunity by means of IL-1β both in IAV and MRSA infection respectively. However, the detailed activity and effect of NLRP3 inflammasome in aggravated pathology of lung in MRSA pneumonia secondary to IAV infection remain under debate. Methods: MRSA infection secondary to IAV was carried out both in vitro and in vivo in this research. Groups were set as blank group, IAV 1w group, and IAV 1w + MRSA 24h group both in murine macrophages and in mice. Then the expression of NLRP3, caspase-1, cleaved caspase-1, IL-1β and pathological change in lung were investigated by means of RT-qPCR, immunofluorescence, Western blot, ELISA and pathology. Results: The results firstly indicated that IAV infection for one week activated NLRP3 inflammasome, and MRSA infection secondary to IAV enhanced the expression of NLRP3, caspase-1 and cleaved caspase-1, but depressed the expression of IL-1β in vitro. The pneumonia model of mice was established successfully. The data of research in mice confirmed the findings in vitro. And worse condition of mice underwent secondary MRSA infection was in accordance with more severe inflammatory pathology in lung. Conclusion: Aggravated inflammatory pathology in MRSA pneumonia secondary to IAV infection diverged from decreased expression of IL-1β, which implied that excessive inflammatory pathology of lung was independent of IL-1β.

Background: Dengue fever has become a major threat to human beings in tropical and subtropical areas, especially severe dengue (SD). It’s of great necessity to search early parameters to identify SD. Lung involvement was increasingly observed in SD. The types of lung involvement include symptoms of cough, breathlessness and hemoptysis, et al, and chest radiographic findings.This study aimed to explore the suggestive role of lung involvement in recognizing SD. Methods: 592 dengue patients admitted in the Third Affiliated Hospital of Sun Yat-sen University from July 2014 to January 2020 were enrolled. Patients were divided into dengue with lung involvement (DWLI) group and dengue without lung involvement (DWOLI) group. According to the severity of dengue fever, patients in DWLI group were further divided into dengue subgroup and SD subgroup. The clinical data were analyzed and compared between groups and subgroups respectively. Results: The rate of SD was higher in DWLI group (p<0.05). Symptoms of cough and breathlessness were more common in DWLI group (both p<0.01). Patients in SD subgroup had higher frequency of cough and breathlessness as well (both p<0.05). The ratios of inflammatory infiltration and pleural effusion in chest radiographic findings were higher in SD subgroup (both p<0.01), and bilateral inflammatory infiltration was correlated with SD (p=0.025). 10 cases in DWLI group complicated with MODS and 2 of them died, while no MODS and death occured in DWOLI group. Conclusions: Our results suggest that types of lung involvement including symptoms of cough and breathlessness, and chest radiographic findings of pleural effusion and bilateral inflammatory infiltration were clues for recognizing SD.