Chlamydia trachomatis ct143 stimulates secretion of proinflammatory cytokines via activating the p38/MAPK signal pathway in THP-1 cells

Proteomic analysis of HeLa cells after stable transfection with the Chlamydia trachomatis CT143 gene

BACKGROUND

The CT143 protein of Chlamydia trachomatis (Ct) is a key immunodominant antigen and candidate type-III secretion substrate. Although CT143 expression has not been detected in the cytosol of infected cells, it is known to interfere with the physiological behavior of HeLa cells. This study aims to investigate how the CT143 protein affects the protein expression profile of HeLa cells, providing a basis for further research into Ct's pathogenic mechanisms.

METHODS

We constructed a stably transfected HeLa cell line, pCD513B-1-CT143-HeLa, and a control cell line, pCD513B-1-HeLa. Protein expression profiles of these cell lines were determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Differentially expressed proteins were identified, constructed into a database, and verified using parallel reaction monitoring (PRM). Bioinformatics software facilitated the preliminary analysis of the biological functions of these differential proteins.

RESULTS

A total of 221 host proteins were differentially expressed, with 68 upregulated and 153 downregulated. These variations influence the regulation of peptidase activity and are crucial in biological processes such as cell secretion and protease activity. Significant changes were noted in protein processing, alcohol dehydrogenase activity, Aldo-Keto reductase activity, and peptidase regulator activity. Furthermore, alterations were observed in cellular components like the plasma membrane and cell periphery. Pathways involving the hematopoietic system, glycosaminoglycan degradation, retinol metabolism, and cytochrome P450-mediated exogenous drug metabolism were notably affected. Indirect interactions among differentially expressed proteins included three key nodal proteins: C3, IFIT3, and IFIT1.

CONCLUSION

The successful construction of a host differential protein expression profile was achieved through stable transfection of HeLa cells with the CT143 gene. The differential proteins identified are implicated in regulating various biological processes such as intracellular signal transduction, cell secretion, protein processing, hydrolysis, and enzyme activity. These findings suggest that the CT143 protein may influence the host cell's biological behavior by altering host protein expression, potentially hindering Ct growth and development.

Chlamydia trachomatis T3SS Effector CT622 Induces Proinflammatory Cytokines Through TLR2/TLR4-Mediated MAPK/NF-κB Pathways in THP-1 Cells

BACKGROUND

The pathogenesis of Chlamydia trachomatis is associated with the induction of the host inflammatory response; however, the precise underlying molecular mechanisms remain poorly understood.

METHODS

CT622, a T3SS effector protein, has an important role in the pathogenesis of C trachomatis; however, whether CT622 can induce a host inflammatory response is not understood. Our findings demonstrate that CT622 induces the expression of interleukins 6 and 8 (IL-6 and IL-8). Mechanistically, these effects involve the activation of the MAPK/NF-κB signaling pathways (mitogen-activated protein kinase/nuclear factor κB).

RESULTS

Interestingly, we demonstrated that the suppression of toll-like receptor 4 using small interfering RNA markedly reduced the phosphorylation of ERK, p38, JNK, and IκBα, concomitant with a significant decrease in IL-6 and IL-8 secretion. Conversely, disruption of toll-like receptor 2 abrogated the CT622-induced upregulation of IL-8 and activation of ERK, whereas IL-6 expression and p38, JNK, and IκBα phosphorylation were unaffected.

CONCLUSIONS

Taken together, these results indicate that CT622 contributes to the inflammatory response through the toll-like receptor 2/4-mediated MAPK/NF-κB pathways, which provides insight into the molecular pathology of C trachomatis infection.

Chlamydia psittaci hypothetical inclusion membrane protein CPSIT_0842 evokes a pro-inflammatory response in monocytes via TLR2/TLR4 signaling pathways

Chlamydia psittaci (C. psittaci) is an obligate intracellular pathogen that resides within a membrane-bound compartment known as the inclusion. Upon entering the host cell, Chlamydiae secrete numerous proteins to modify the inclusion membrane. Inclusion membrane (Inc) proteins are important pathogenic factors in Chlamydia and play crucial roles in the growth and development of Chlamydia. In the present study, the C. psittaci protein, CPSIT_0842, was identified and shown to localize to the inclusion membrane. Temporal analysis revealed that CPSIT_0842 is an early expression protein of Chlamydia. Moreover, this protein was shown to induce the expression of pro-inflammatory cytokines IL-6 and IL-8 in human monocytes (THP-1 cells) via the TLR2/TLR4 signaling pathway. CPSIT_0842 increases the expression of TLR2, TLR4, and adaptor MyD88. Suppression of TLR2, TLR4, and MyD88 markedly attenuated CPSIT_0842-induced production of IL-6 and IL-8. MAP kinases and NF-κB, important downstream molecules of TLR receptors in inflammatory signaling pathways, were also confirmed to be activated by CPSIT_0842. CPSIT_0842-induced production of IL-6 was reliant on activation of the ERK, p38, and NF-κB signaling pathways while IL-8 expression was regulated by the ERK, JNK, and NF-κB signaling pathways. Specific inhibitors of these signaling pathways significantly decreased CPSIT_0842-mediated expression of IL-6 and IL-8. Together these findings demonstrate that CPSIT_0842 upregulates the expression of IL-6 and IL-8 via TLR-2/TLR4-mediated MAPK and NF-κB signaling pathways in THP-1 cells. Exploring these molecular mechanisms enhances our understanding of C. psittaci pathogenesis.

Integrating lncRNAs and mRNAs Expression Profiles in Penicillin-Induced Persistent Chlamydial Infection in HeLa Cells

Chlamydia trachomatis (C. trachomatis) is a major etiological agent of sexually transmitted infection. Some stressing conditions can result in persistent chlamydial infection, which is thought to be associated with severe complications including ectopic pregnancy and tubal factor infertility. Long noncoding RNAs (lncRNAs) have been identified as key modulators in many biological processes. Nevertheless, the role of lncRNAs in persistent chlamydial infection is still unclear. In this study, we used lncRNA and mRNA microarray to identify the global lncRNAs and mRNAs expression in penicillin-induced persistent chlamydial infection in HeLa cells as well as the control group (HeLa cells without C. trachomatis infection). Among 1005 differentially expressed lncRNAs, 585 lncRNAs were upregulated and 420 downregulated in persistent chlamydial infection, while 410 mRNAs were identified to express differentially, of which 113 mRNAs were upregulated and 297 downregulated. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis with differentially expressed genes were performed. We then constructed the lncRNA-miRNA-mRNA competing endogenous RNAs (ceRNAs) network. Four mRNAs were validated to be changed by quantitative real-time PCR which were correlated with the microarray result. Integration of protein-protein interaction network was constructed and hub genes were identified. These findings provide a new perspective on the molecular mechanisms of penicillin-induced persistent chlamydial infection.

Chlamydia trachomatis glycogen synthase promotes MAPK-mediated proinflammatory cytokine production via TLR2/TLR4 in THP-1 cells

AIMS

To investigate the roles and mechanisms of C. trachomatis glycogen synthase (GlgA) in regulating the inflammatory response in THP-1 cells.

MAIN METHODS

In this work, after THP-1 cells were stimulated with GlgA, transcript and protein expression levels were measured by qRT-PCR and ELISA, respectively. Western blotting and immunofluorescence were used to determine the signaling pathway involved in the inflammatory mechanism.

KEY FINDINGS

GlgA elicited the expression of interleukin-8 (IL-8), interleukin-1beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in THP-1 cells, and the blockade of TLR2 and TLR4 signaling abrogated the induction of IL-8, TNF-α and IL-1β expression. Similarly, IL-8, IL-1β and TNF-α secretion was reduced by transfection with a dominant negative plasmid (pDeNyhMyD88). Moreover, Western blotting and immunofluorescence experiments further validated that MAPKs and NF-кB signaling are involved in the transcription and translation of these cytokines. Treatment of the cells with ERK and JNK inhibitors dramatically attenuated the induction of IL-8, IL-1β and TNF-α.

SIGNIFICANCE

These results suggest that GlgA contributes to inflammation during C. trachomatis infection via the TLR2, TLR4 and MAPK/NF-кB pathways, which may enhance our understanding of the pathogenesis of C. trachomatis.

iTRAQ-Based Quantitative Proteomics Analysis of HeLa Cells Infected With Chlamydia muridarum TC0668 Mutant and Wild-Type Strains

Chlamydia muridarum, an obligate intracellular pathogen, was used to establish a murine model of female upper genital tract infection by Chlamydia trachomatis. TC0668 in C. muridarum is a hypothetical chromosomal virulence protein that is involved in upper genital tract pathogenesis. The infection of mice with the C. muridarum TC0668-mutant (G216*) strain results in less pathological damage in the upper genital tract. In this study, an isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics analysis was performed to identify differentially expressed proteins between TC0668 wild-type (TC0668^wt) and TC0668 mutant (TC0668^mut) strains at 6, 12, 18, and 24 h post-infection (p.i.). Of the 550 proteins differentially expressed at 18 h p.i., 222 and 328 were up-regulated and down-regulated, respectively, inTC0668^mut-infected cells. The expression of seven up-regulated proteins (encoded by SRPRB, JAK1, PMM1, HLA-DQB1, THBS1, ITPR1, and BCAP31) and three down-regulated proteins (encoded by MAPKAPK2, TRAFD1, and IFI16) from the iTRAQ analysis were validated using quantitative real-time (qRT)-PCR. The qRT-PCR results were consistent with those of iTRAQ. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that the differentially expressed proteins primarily participated in inflammatory responses, fibrosis, metabolic processes, and complement coagulation cascades, and were mainly enriched in the phosphatidylinositol 3′-kinase (PI3K)/Akt, nuclear factor kappa-B (NF-κB), and other signaling pathways. Using western-blotting and immunofluorescence detection, significant differences in activation of the PI3K/Akt and NF-κB signaling pathways were observed between the TC0668^wt- and TC0668^mut-infected cells. Differentially expressed proteins linked with inflammation and fibrosis were used in a protein-protein interaction network analysis. The results suggest that TC0668 may play a pivotal role in C. muridarum-induced genital pathology by inducing inflammatory responses and fibrosis, which may involve the activation of the PI3K/Akt and NF-κB signaling pathways.

The multiple functions of the numerous Chlamydia trachomatis secreted proteins: the tip of the iceberg

Chlamydia trachomatis serovars are obligate intracellular bacterial pathogens mainly causing ocular and urogenital infections that affect millions of people worldwide and which can lead to blindness or sterility. They reside and multiply intracellularly within a membrane-bound vacuolar compartment, known as inclusion, and are characterized by a developmental cycle involving two morphologically and physiologically distinct chlamydial forms. Completion of the developmental cycle involves the secretion of > 70 C. trachomatis proteins that function in the host cell cytoplasm and nucleus, in the inclusion membrane and lumen, and in the extracellular milieu. These proteins can, for example, interfere with the host cell cytoskeleton, vesicular and non-vesicular transport, metabolism, and immune signalling. Generally, this promotes C. trachomatis invasion into, and escape from, host cells, the acquisition of nutrients by the chlamydiae, and evasion of cell-autonomous, humoral and cellular innate immunity. Here, we present an in-depth review on the current knowledge and outstanding questions about these C. trachomatis secreted proteins.