Exogenous Hydrogen Sulfide Regulates Mycoplasma pneumoniae Lipid-Associated Membrane Proteins to Induce Expression of Heme Oxygenase-1 and Proinflammatory Cytokines.

This study was designed to investigate the effect of exogenous hydrogen sulfide (H2S) on the secretion of Heme oxygenase (HO-1) and proinflammatory cytokines in human mononuclear cell line THP-1 stimulated by lipid-associated membrane proteins (LAMPs) prepared from Mycoplasma pneumoniae (M. pneumoniae) and explore its regulatory mechanism. Cultured cells were stimulated with M. pneumoniae LAMPs after pretreatment with H2S to analyze the production of proinflammatory cytokines and HO-1 by enzyme-linked immunosorbent assay (ELISA) and Western blot. The results showed that THP-1 cells, which were stimulated by LAMPs after pretreatment with H2S, had decreased production of interleukin-6 (IL-6) and interleukin-8 (IL-8) by inhibiting the mitogen-activated protein kinases (MAPKs)/nuclear factor-kappa B (NF-κB) signaling pathway and increased expression of HO-1 by activating the nuclear factor E2-related factor 2 (Nrf2) signaling pathway. Our results indicate that H2S may play an important role in attenuating inflammation induced by M. pneumoniae LAMPs due to its ability to decrease the production of IL-6 and IL-8 and increase the expression of the HO-1. These findings support further studies for possible clinical applications.

High expression of HMGB1 in children with refractory Mycoplasma pneumoniae pneumonia.

BACKGROUND: Increasing numbers of refractory or severe, even fatal, cases of Mycoplasma pneumoniae infections have been reported in recent years. Excessive inflammatory responses play a vital role in the pathogenesis of refractory M. pneumoniae pneumonia (RMPP). HMGB1 is an actively secreted cytokine produced by macrophages and other inflammatory cells that participates in various infectious diseases. The present study aimed to explore the role and clinical significance of HMGB1 in children with RMPP and the potential mechanism of HMGB1 expression. METHODS: Four hundred and fifty-two children diagnosed with M. pneumoniae pneumonia, including 108 children with RMPP, were enrolled from January 2013 to December 2015 at the Children's Hospital of Soochow University. HMGB1, TNF-α, and IL-6 in peripheral blood from RMPP and non-RMPP (NRMPP) cases were detected by real-time PCR and ELISA. Lipid-associated membrane proteins (LAMPs) were extracted from live M. pneumoniae and prepared at different concentrations for stimulation of THP-1 cells. After coculture with LAMPs, HMGB1, TNF-α, IL-6, RAGE, TLR2, and TLR4 in THP-1 cells were detected by real-time PCR. RESULTS: Occurrences of cough, fever, and abnormal lung signs were more frequent in RMPP cases compared with NRMPP cases (all p < 0.05). Children with RMPP had longer hospital stays than children with NRMPP (p < 0.05). Different distributions of lymphocytes were noted between RMPP and NRMPP cases. HMGB1, TNF-α, and IL-6 levels were significantly higher in RMPP cases compared with NRMPP cases (all p < 0.05). HMGB1 had good diagnostic ability to differentiate RMPP with AUC of 0.876, sensitivity of 0.833, and specificity of 0.824 compared with TNF-α and IL-6. HMGB1 expression in THP-1 cells was increased by stimulation with 10 µg/ml LAMPs. TLR2 expression was increased after stimulation with 6 µg/ml LAMPs. HMGB1 level was positively associated with TNF-α, IL-6, and TLR2 levels. CONCLUSIONS: HMGB1 is a good diagnostic biomarker for differentiating RMPP and NRMPP. LAMPs from M. pneumoniae may induce HMGB1 expression in immune cells through the TLR2 pathway. Further in vitro and in vivo studies are needed for the development of a new treatment strategy to inhibit the HMGB1 pathway, thereby preventing the inflammation in RMPP.

Ureaplasma spp. lipid-associated membrane proteins induce human monocyte U937 cell cycle arrest through p53-independent p21 pathway.

Ureaplasma spp. are known to be associated with human genitourinary tract diseases and perinatal diseases and Ureaplasma spp. Lipid-associated membrane proteins (LAMPs) play important roles in their related diseases. However, the exact mechanism underlying pathogenesis of Ureaplasma spp. LAMPs is largely unknown. In this study, we explored the pathogenic mechanisms of Ureaplasma spp. LAMPs by elucidating their role in modulating the cell cycle and related signaling pathways in human monocytic cell U937, which is highly related to the inflammatory and protective effect in infectious diseases. We utilized the two ATCC reference strains (Ureaplasma parvum serovar 3 str. ATCC 27,815 (UPA3) and Ureaplasma urealyticum serovar 8 str. ATCC 27,618 (UUR8)) and nine clinical isolates which including both UPA and UUR to study the effects of Ureaplasma spp. LAMPs on U937 in vitro. We found that LAMPs derived from UUR8 and both UPA and UUR of clinical strains markedly inhibited the cell proliferation, while UPA3 LAMPs suppressed slightly. Besides, the result of flow cytometry analysis indicated all the Ureaplasma spp. LAMPs could arrest U937 cells in G1 phase. Next, we found that the cell cycle arrest was associated with increased levels of p53 and p21, and a concomitant decrease in the levels of CDK2, CDK4, CDK6 and cyclin E1 at both transcriptional and translational levels after treatment with LAMPs derived from UUR8 or clinical strains, while only cyclin E1 was down-regulated after treatment with UPA3 LAMPs. Further study showed that p53 down-regulation had almost no effect on the distribution of cell cycle and the expression of p21. In conclusion, this study demonstrated that LAMPs derived from UUR8 and clinical strains could inhibit the proliferation of U937 cells by inducing G1 cell cycle arrest through increasing the p21 expression in a p53-independent manner, while UPA3 LAMPs could induce the cell cycle arrest slightly. Our study could contribute to the understanding of Ureaplasma spp. pathogenesis, which has potential value for the treatment of Ureaplasma spp. infections.

Nrf2 regulates the inflammatory response, including heme oxygenase-1 induction, by mycoplasma pneumoniae lipid-associated membrane proteins in THP-1 cells.

A series of inflammatory responses caused by Mycoplasma pneumoniae largely depend on the lipid-associated membrane proteins (LAMPs). Nuclear factor E2-related factor 2 (Nrf2), a transcription factor, is considered to be a critical modulator of inflammatory responses and cellular redox homeostasis. Monocytes play an important role in the invasion and immunity to resist pathogens. Here, we investigated the role of Nrf2 in the anti-inflammatory response stimulated by LAMPs using the human monocyte cell line THP-1. LAMPs were shown to affect the localization of Nrf2, and the levels of reactive oxygen species and inflammatory reactants, including nitric oxide (NO), prostaglandin E2 (PGE2) and cytokines (IL-6, IL-8), were highly elevated in LAMP-stimulated Nrf2-silenced THP-1 cells. Moreover, LAMPs induced the levels of mRNA and the expression of heme oxygenase-1 (HO-1). In summary, our results demonstrated that LAMPs cause nuclear translocation of Nrf2, which further suppresses the expression of inflammatory reactants in THP-1 cells.

The lipid-associated membrane proteins derived from Mycoplasma pneumoniae strains induced the expression of HO-1 in THP-1 cells / 中华微生物学和免疫学杂志

Objective To investigate the effects of lipid-associated membrane proteins ( LAMPs) derived from Mycoplasma pneumoniae ( M.pneumoniae) strains on the expression of heme oxygenase 1 ( HO-1) in a human monocyte cell line (THP-1).Methods THP-1 cells were in vitro cultured with different concentrations of LAMPs for different times.The cytotoxicity of LAMPs to THP-1 cells was analyzed by using lactate dehydrogenase ( LDH) releasing test.The expression of HO-1 at protein and mRNA levels were de-tected by Western blot and real-time RT-PCR, respectively.The enzymatic activity of HO-1 protein was ex-amined by colorimetric assay.THP-1 cells stimulated with PBS and LPS were set up as the negative and pos-itive controls, respectively.Results A significantly enhanced LDH releasing rate was observed in THP-1 cells treated with 10 μg/ml of LAMPs.The expression of HO-1 at protein and mRNA levels in THP-1 cells were induced by LAMPs in a dose-dependent and time-dependent manner.The highest level of HO-1 protein was detected in THP-1 cells treated with 5.0 μg/ml of LAMPs.The transcriptional levels of HO-1 induced by LAMPs were significantly elevated at 3 h, peaked at 9 h and were decreased at 12 h.The expression of HO-1 protein in THP-1 cells was enhanced after 8 h of treatment with LAMPs and a significant decrease was observed at 20 h after reaching peaks at 12 h and 16 h.The activity of HO-1 protein was significantly en-hanced along with the increased expression of HO-1 protein.Conclusion The LAMPs derived from M.pneumoniae strains induced the expression of HO-1 at mRNA and protein levels.Moreover, the enzyme activity of HO-1 protein was enhanced in LAMPs treated THP-1 cells.