Involvement of MAPK activation in chemokine or COX-2 productions by Toxoplasma gondii

The roles of COX-2 in protozoan infection

Protozoan diseases cause great harm in animal husbandry and require human-provided medical treatment. Protozoan infection can induce changes in cyclooxygenase-2 (COX-2) expression. The role played by COX-2 in the response to protozoan infection is complex. COX-2 induces and regulates inflammation by promoting the synthesis of different prostaglandins (PGs), which exhibit a variety of biological activities and participate in pathophysiological processes in the body in a variety of ways. This review explains the roles played by COX-2 in protozoan infection and analyzes the effects of COX-2-related drugs in protozoan diseases.

Inhibitory Effects of Inonotus obliquus Polysaccharide on Inflammatory Response in Toxoplasma gondii-Infected RAW264.7 Macrophages

Our previous reports have shown that Inonotus obliquus polysaccharide (IOP) has protective effects against Toxoplasma gondii (T. gondii) infection in vivo. The aim of the present research is to explore the in vitro anti-inflammatory effects of IOP and its mechanism in RAW264.7 macrophages infected by T. gondii. In this study, it is indicated that IOP decreased the excessive secretion of inflammatory cytokines tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-1β (IL-1β), IL-4, and IL-6 in T. gondii-infected RAW264.7 macrophages. IOP effectively suppressed the mRNA expression of these cytokines and chemokines monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1α (MIP-1α). Moreover, IOP inhibited the phosphorylation of inhibitor kappa B kinase α/β (IKKα/β), inhibitor κBα (IκBα), p65 in nuclear factor-kappa B (NF-κB) signaling pathway and p38, c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase 1/2 (ERK1/2) in mitogen-activated protein kinases (MAPKs) signaling pathway. Meantime, IOP prevented NF-κB p65 and c-Jun translocation from the cytoplasm to the nucleus. Further, IOP downregulated the protein expression of toll-like receptor 2 (TLR2) and TLR4 in T. gondii-infected RAW264.7 macrophages. The above results suggest that IOP can inhibit the inflammatory response infected with T. gondii via regulating TLR2/TLR4-NF-κB/MAPKs pathways and exerting its anti-T. gondii role in vitro.

Immunomodulatory effects of Inonotus obliquus polysaccharide on splenic lymphocytes infected with Toxoplasma gondii via NF-κB and MAPKs pathways

CONTEXT

As a medicinal and edible fungus, Inonotus obliquus has been traditionally used to prevent and treat various ailments. Inonotus obliquus polysaccharide (IOP) isolated from I. obliquus processes many biological activities, our series of in vivo studies have shown that IOP protects against Toxoplasma gondii infection.

OBJECTIVE

This study aimed to investigate the in vitro immunomodulatory effects and its mechanisms of IOP on mouse splenic lymphocytes infected with T. gondii.

MATERIALS AND METHODS

Mouse splenic lymphocytes were infected with T. gondii tachyzoites, and treated with different concentrations of IOP. The levels of cytokines and chemokines were measured by enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR). The expression of toll-like receptor 2 (TLR2) and TLR4, and the modulation of nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs) signaling pathways were determined by Western blot.

RESULTS

IOP significantly decreased the over-release of cytokine interleukin-1 beta (IL-1β), IL-4, IL-6, interferon-gamma (IFN-γ), and tumor necrosis factor-alpha (TNF-α) in supernatant from T. gondii-infected splenic lymphocytes. IOP also effectively inhibited the overexpression of cytokines and chemokine macrophage inflammatory protein-1 (MIP-1) and monocyte chemoattractant protein-1 (MCP-1) mRNA. Furthermore, IOP down-regulated TLR2 and TLR4 expressions and inhibited the over-phosphorylation of NF-κB p65 and inhibitor κBα (IκBα) in NF-κB signaling pathway and p38, c-Jun N-terminal kinase (JNK) in MAPKs signaling pathway. By observing the effect of IOP on TNF-α secretion after pretreatment with specific inhibitors, it was further confirmed that IOP was involved in the regulation of NF-κB, p38, and JNK signaling pathways.

CONCLUSIONS

These data indicate that IOP can inhibit the excessive inflammatory response caused by T. gondii infection through modulating NF-κB, p38, and JNK signaling pathways, and thus plays the in vitro anti-T. gondii role.

Regulation of Proinflammatory Enzymes by Peroxisome Proliferator-Activated Receptor Gamma in Astroglia Infected with Toxoplasma gondii

Peroxisome proliferator-activated receptor gamma (PPARγ) regulates neuroinflammation, and its agonists act as neuroprotective agents. This study aims to investigate the correlation between PPARγ and proinflammatory enzyme expression in astroglia infected with Toxoplasma gondii tachyzoite in vitro. Our results showed that matrix metalloprotease (MMP)-2, MMP-9, cyclooxygenase-2 (COX-2), prostaglandin (PGE)-2, inducible nitric-oxide synthase (iNOS), and nitric oxide (NO) were significantly increased in T. gondii-infected astroglia. Furthermore, the expression levels of MMP-2, MMP-9, COX-2, PGE-2, iNOS, and NO were significantly decreased by rosiglitazone-a PPARγ agonist. By contrast, the treatment with GW9662, a PPARγ antagonist, efficiently increased the expression levels of MMP-2, MMP-9, COX-2, PGE-2, iNOS, and NO. These results suggested that the treatment with rosiglitazone offers a potential strategy for controlling the inflammatory factors in T. gondii infection.

Increased Toxoplasma gondii Intracellular Proliferation in Human Extravillous Trophoblast Cells (HTR8/SVneo Line) Is Sequentially Triggered by MIF, ERK1/2, and COX-2

Macrophage migration inhibitory factor (MIF) is a potent pro-inflammatory cytokine, which mediates the regulation of diverse cellular functions. It is produced by extravillous trophoblastic cells and has been found to be involved in the pathogenesis of diseases caused by some protozoa, including Toxoplasma gondii. Previous studies demonstrated the ability of T. gondii to take advantage of MIF action in human trophoblast cells. However, MIF action in T. gondii-infected extravillous trophoblastic cells (HTR8/SVneo cell line) has not been fully investigated. The present study aimed to investigate the role of MIF in T. gondii-infected HTR8/SVneo cells and verify the intracellular signaling pathways triggered by this cytokine. We found that T. gondii increased MIF production by HTR8/SVneo cells, and by contrast, MIF inhibition, by ISO-1, led to a significant decrease in T. gondii proliferation and CD74 expression in HTR8/SVneo cells. Moreover, in infected HTR8/SVneo cells, the addition of recombinant MIF (rMIF) increased CD44 co-receptor expression, ERK1/2 phosphorylation, COX-2 expression, and IL-8 production, which favored T. gondii proliferation. Our findings indicate that T. gondii can use MIF to modulate important factors in HTR8/SVneo cells, being a possible explanation for the higher susceptibility of extravillous trophoblast cells than other trophoblast cell populations.

Cyclooxygenase (COX)-2 Inhibitors Reduce Toxoplasma gondii Infection and Upregulate the Pro-inflammatory Immune Response in Calomys callosus Rodents and Human Monocyte Cell Line

Toxoplasma gondii is able to infect a wide range of vertebrates, including humans. Studies show that cyclooxygenase-2 (COX-2) is a modulator of immune response in multiple types of infection, such as Trypanosoma cruzi. However, the role of COX-2 during T. gondii infection is still unclear. The aim of this study was to investigate the role of COX-2 during infection by moderately or highly virulent strains of T. gondii in Calomys callosus rodents and human THP-1 cells. C. callosus were infected with 50 cysts of T. gondii (ME49), treated with COX-2 inhibitors (meloxicam or celecoxib) and evaluated to check body weight and morbidity. After 40 days, brain and serum were collected for detection of T. gondii by real-time PCR and immunohistochemistry or cytokines by CBA. Furthermore, peritoneal macrophages or THP-1 cells, infected with RH strain or uninfected, were treated with meloxicam or celecoxib to evaluate the parasite proliferation by colorimetric assay and cytokine production by ELISA. Finally, in order to verify the role of prostaglandin E₂ in COX-2 mechanism, THP-1 cells were infected, treated with meloxicam or celecoxib plus PGE₂, and analyzed to parasite proliferation and cytokine production. The data showed that body weight and morbidity of the animals changed after infection by T. gondii, under both treatments. Immunohistochemistry and real-time PCR showed a reduction of T. gondii in brains of animals treated with both COX-2 inhibitors. Additionally, it was observed that both COX-2 inhibitors controlled the T. gondii proliferation in peritoneal macrophages and THP-1 cells, and the treatment with PGE₂ restored the parasite growth in THP-1 cells blocked to COX-2. In the serum of Calomys, upregulation of pro-inflammatory cytokines was detected, while the supernatants of peritoneal macrophages and THP-1 cells demonstrated significant production of TNF and nitrite, or TNF, nitrite and MIF, respectively, under both COX-2 inhibitors. Finally, PGE₂ treatment in THP-1 cells triggered downmodulation of pro-inflammatory mediators and upregulation of IL-8 and IL-10. Thus, COX-2 is an immune mediator involved in the susceptibility to T. gondii regardless of strain or cell types, since inhibition of this enzyme induced control of infection by upregulating important pro-inflammatory mediators against Toxoplasma.

A Human Proteome Array Approach to Identifying Key Host Proteins Targeted by Toxoplasma Kinase ROP18

Toxoplasma kinase ROP18 is a key molecule responsible for the virulence of Toxoplasma gondii; however, the mechanisms by which ROP18 exerts parasite virulence via interaction with host proteins remain limited to a small number of identified substrates. To identify a broader array of ROP18 substrates, we successfully purified bioactive mature ROP18 and used it to probe a human proteome array. Sixty eight new putative host targets were identified. Functional annotation analysis suggested that these proteins have a variety of functions, including metabolic process, kinase activity and phosphorylation, cell growth, apoptosis and cell death, and immunity, indicating a pleiotropic role of ROP18 kinase. Among these proteins, four candidates, p53, p38, UBE2N, and Smad1, were further validated. We demonstrated that ROP18 targets p53, p38, UBE2N, and Smad1 for degradation. Importantly, we demonstrated that ROP18 phosphorylates Smad1 Ser-187 to trigger its proteasome-dependent degradation. Further functional characterization of the substrates of ROP18 may enhance understanding of the pathogenesis of Toxoplasma infection and provide new therapeutic targets. Similar strategies could be used to identify novel host targets for other microbial kinases functioning at the pathogen-host interface.

Toxoplasma gondii GRA7-Induced TRAF6 Activation Contributes to Host Protective Immunity

The intracellular parasite Toxoplasma gondii has unique dense granule antigens (GRAs) that are crucial for host infection. Emerging evidence suggests that GRA7 of T. gondii is a promising serodiagnostic marker and an effective toxoplasmosis vaccine candidate; however, little is known about the intracellular regulatory mechanisms involved in the GRA7-induced host responses. Here we show that GRA7-induced MyD88 signaling through the activation of TRAF6 and production of reactive oxygen species (ROS) is required for the induction of NF-κB-mediated proinflammatory responses by macrophages. GRA7 stimulation resulted in the rapid activation of mitogen-activated protein kinases and an early burst of ROS in macrophages in a MyD88-dependent manner. GRA7 induced a physical association between GRA7 and TRAF6 via MyD88. Remarkably, the C terminus of GRA7 (GRA7-V) was sufficient for interaction with and ubiquitination of the RING domain of TRAF6, which is capable of inflammatory cytokine production. Interestingly, the generation of ROS and TRAF6 activation are mutually dependent on GRA7/MyD88-mediated signaling in macrophages. Furthermore, mice immunized with GRA7-V showed markedly increased Th1 immune responses and protective efficacy against T. gondii infection. Collectively, these results provide novel insight into the crucial role of GRA7-TRAF6 signaling in innate immune responses.

Transcriptional Regulation of CXCL5 in HIV-1-Infected Macrophages and Its Functional Consequences on CNS Pathology

Human immunodeficiency virus-1 (HIV-1)-infected monocytes/macrophages and microglia release increased levels of proinflammatory cytokines and chemokines, including ELR+ (containing glutamic acid-leucine-arginine motif) chemokines. To investigate the role of HIV-1 infection on chemokine regulation, monocyte-derived macrophages (MDMs) from normal donors were infected with HIV-1 and the expression of chemokines and their downstream biological functions were evaluated. Among the tested chemokines, CXCL5 was upregulated significantly both at the mRNA and protein level in the HIV-1-infected MDMs compared with mock-infected cultures. Upregulation of CXCL5 in the HIV-1-infected MDMs is, in part, regulated by increased interleukin-1β (IL-1β) production and phosphorylation of ERK1/2. Functional analyses indicate that HIV-1-induced overexpression of CXCL5 has enhanced the ability to attract neutrophils, as observed by chemotaxis assay. However, exposure of NT2, SH-SY5Y cells, and primary neurons to HIV-1-infected MDM supernatants resulted in cell death that was not rescued by anti-CXCL5 antibody suggesting that CXCL5 does not have direct effect on neuronal death. Together, these results suggest that the increased level of CXCL5 in tissue compartments, including the central nervous system of HIV-1-infected individuals might alter the inflammatory response through the infiltration of neutrophils into tissue compartment, thus causing secondary effects on resident cells.

Differential regulation of proinflammatory cytokine expression by mitogen-activated protein kinases in macrophages in response to intestinal parasite infection

Blastocystis is a common enteric protistan parasite that can cause acute, as well as chronic, infection and is associated with irritable bowel syndrome (IBS). However, the pathogenic status of Blastocystis infection remains unclear. In this study, we found that Blastocystis antigens induced abundant expression of proinflammatory cytokines, including interleukin 1β (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α), in mouse intestinal explants, in mouse colitis colon, and in macrophages. Further investigation utilizing RAW264.7 murine macrophages showed that Blastocystis treatment in RAW264.7 macrophages induced the activation of ERK, JNK, and p38, the three major groups of mammalian mitogen-activated protein (MAP) kinases that play essential roles in the expression of proinflammatory cytokines. ERK inhibition in macrophages significantly suppressed both mRNA and protein expression of IL-6 and TNF-α and mRNA expression of IL-1β. On the other hand, JNK inhibition resulted in reductions in both c-Jun and ERK activation and significant suppression of all three proinflammatory cytokines at both the mRNA and protein levels. Inhibition of p38 suppressed only IL-6 protein expression with no effect on the expression of IL-1β and TNF-α. Furthermore, we found that serine proteases produced by Blastocystis play an important role in the induction of ERK activation and proinflammatory cytokine expression by macrophages. Our study thus demonstrated for the first time that Blastocystis could induce the expression of various proinflammatory cytokines via the activation of MAP kinases and that infection with Blastocystis may contribute to the pathogenesis of inflammatory intestinal diseases through the activation of inflammatory pathways in host immune cells, such as macrophages.

Recurrent headaches may be caused by cerebral toxoplasmosis

AIM

To establish seroprevalence and provide characteristics of Toxoplasma gondii (TG) infection in children with recurrent headaches.

METHODS

The study was performed in 178 children aged 7-17 years admitted consecutively to the Department of Pediatric Neurology from November 2009 to July 2011. The children were surveyed with a questionnaire with the help and assistance of their parents and blood samples taken on admission were studied for the presence of specific anti-TG IgM, IgG antibodies and IgG avidity using enzyme immunoassay Platelia Toxo IgM, IgG.

RESULTS

The study showed that 19 children (8 boys, 11 girls; 8-17 years old, mean age 14.36 years) had high serum anti-TG IgG antibody levels (range: 32.2 > 240 UI/mL, mean 120.18 UI/mL; positive value for IgG was ≥ 9 UI/mL). The avidity index (AI) ranged from 0.202 to 0.925 (scale: ≥ 0.5 high AI). The results for IgM antibodies were all negative and the obtained results ranged from 0.113 to 0.25 U/mL (mean = 0.191 IU/mL) and all values below 0.8 IU/mL were considered negative. The most frequent complaints found in the seropositive patients were headaches that affected the frontal (13 children), occipital (4) and parietal areas (5). Headaches usually had a pulsating (in 7 patients) and squeezing (6) character and rarely were piercing, dull or expanding. Interestingly, 8 children did not feel discomfort during the headaches, probably because they did not have sufficiently increased intracranial pressure yet. The headaches usually appeared 1-2 times/mo, lasted for 2-6 h, and had a mean intensity of 5.5 points in a 10 point subjective scale. The comorbidities included epilepsy (5 patients), various infections in 3 children (chronic eustachitis, chronic rhinitis, chronic purulent tonsillitis, streptococcal pharyngitis, meningitis, allergic diseases), disturbances of behavior, deficits of attention, and ocular and motor concentration disorders in 1 child. The electroencephalographic and neuroimaging studies performed in our patients had a very limited value in establishing cerebral toxoplasmosis.

CONCLUSION

Ten point six seven percent of the studied children had markedly increased serum anti-TG IgG antibodies and high AI indicated chronic infestation. It is suggested that tests for TG infection should be introduced to routine diagnostics in patients with recurrent headaches.

Induction of matrix metalloproteinase-2 and -9 via Erk1/2-NF-κB pathway in human astroglia infected with Toxoplasma gondii

Matrix metalloproteinase (MMP)-2 and MMP-9 can cleave fibronectin, allowing leukocyte migration to the site of Toxoplasma gondii infection during toxoplasmic encephalitis. The aim of this study was to investigate the association between extracellular signal-regulated kinase (Erk)1/2-nuclear factor (NF)-κB pathway and MMP-2/-9 expression in astroglia infected with T. gondii tachyzoite in vitro. Our results showed that phosphorylated (p)-Erk1/2 transiently increased 1h post-infection (PI) and p-NF-κB significantly increased from 1h PI to 12h PI in cell homogenates. NF-κB was bound directly to oligonucleotides containing putative NF-κB binding sites for the MMP-9 promoter. Additionally, expression of p-NF-κB, MMP-2, and MMP-9 was significantly decreased by MG132, an indirect NF-κB inhibitor. Treatment with PD98059, an Erk kinase inhibitor, efficiently reduced p-Erk1/2, p-NF-κB, MMP-2, and MMP-9 expression. These results suggest that suppression of the Erk1/2-NF-κB signaling pathway causes reductions in MMP-2 and MMP-9 activities in astroglia response to T. gondii infection. Thus, inhibiting this signaling intermediate involved in MMP-2 and MMP-9 expression may be a potential method for controlling inflammatory development of T. gondii-induced encephalitis.

AP-1 pathway-targeted inhibition of inflammatory responses in LPS-treated macrophages and EtOH/HCl-treated stomach by Archidendron clypearia methanol extract

ETHNOPHARMACOLOGICAL RELEVANCE

Archidendron clypearia Jack. (Fabaceae) is a representative ethnomedicinal herbal plant prescribed for various inflammatory diseases such as pharyngolaryngitis and tonsillitis. However, the pharmacology behind this plant's anti-inflammatory properties has not been fully understood. Therefore, in this study, the anti-inflammatory mechanism of a 95% methanol extract (Ac-ME) was explored.

MATERIALS AND METHODS

The anti-inflammatory mechanism of Ac-ME on the AP-1 activation pathway, which plays a critical role in the production of prostaglandin (PG)E2 in RAW264.7 cells and peritoneal macrophages and in induction of acute gastritis caused by HCl/EtOH, was investigated using immunoblotting, immunoprecipitation analyses, and reporter gene activity assays. In particular, enzyme assays and HPLC analysis were employed to identify direct target enzymes of Ac-ME and to detect active chemical components from the plant extract.

RESULTS

Ac-ME clearly reduced the nuclear levels of total and phospho-forms of c-Jun, FRA-1, and ATF-2. Consequently, this extract suppressed both the production of PGE2 in lipopolysaccharide (LPS)-activated RAW264.7 and peritoneal macrophage cells and PGE2-dependent induction of gastritis lesion in stomach under EtOH/HCl exposure. Analysis of AP-1 upstream signalling revealed that the AP-1 activation pathway consisting of IRAK1, TRAF6, TAK1, MKK3/6, and p38 was predominantly inhibited by Ac-ME. Similarly, this extract directly blocked the enzyme activity of IRAK1, indicating that this enzyme is an inhibitory target of Ac-ME and is involved in the suppression of the AP-1 pathway. HPLC analysis showed that quercetin, which inhibits PGE2 production, is an active component in Ac-ME.

CONCLUSION

Ac-ME is an ethnomedicinal remedy with an IRAK1/p38/AP-1-targeted inhibitory property. Since AP-1 is a major inflammation-inducing transcription factor, the therapeutic potential of Ac-ME in other AP-1-mediated inflammatory symptoms will be further tested.

Roles of Apicomplexan protein kinases at each life cycle stage

Inhibitors of cellular protein kinases have been reported to inhibit the development of Apicomplexan parasites, suggesting that the functions of protozoan protein kinases are critical for their life cycle. However, the specific roles of these protein kinases cannot be determined using only these inhibitors without molecular analysis, including gene disruption. In this report, we describe the functions of Apicomplexan protein kinases in each parasite life stage and the potential of pre-existing protein kinase inhibitors as Apicomplexan drugs against, mainly, Plasmodium and Toxoplasma.

Serum response factor regulates immediate early host gene expression in Toxoplasma gondii-infected host cells

Toxoplasma gondii is a wide spread pathogen that can cause severe and even fatal disease in fetuses and immune-compromised hosts. As an obligate intracellular parasite, Toxoplasma must alter the environment of its host cell in order to establish its replicative niche. This is accomplished, in part, by secretion of factors into the host cell that act to modulate processes such as transcription. Previous studies demonstrated that genes encoding transcription factors such as c-jun, junB, EGR1, and EGR2 were amongst the host genes that were the most rapidly upregulated following infection. In cells stimulated with growth factors, these genes are regulated by a transcription factor named Serum Response Factor. Serum Response Factor is a ubiquitously expressed DNA binding protein that regulates growth and actin cytoskeleton genes via MAP kinase or actin cytoskeletal signaling, respectively. Here, we report that Toxoplasma infection leads to the rapid activation of Serum Response Factor. Serum Response Factor activation is a Toxoplasma-specific event since the transcription factor is not activated by the closely related protozoan parasite, Neospora caninum. We further demonstrate that Serum Response Factor activation requires a parasite-derived secreted factor that signals via host MAP kinases but independently of the host actin cytoskeleton. Together, these data define Serum Response Factor as a host cell transcription factor that regulates immediate early gene expression in Toxoplasma-infected cells.

Toxoplasma gondii rhoptry discharge correlates with activation of the early growth response 2 host cell transcription factor

Toxoplasma gondii is a ubiquitous apicomplexan parasite that can cause severe disease in fetuses and immune-compromised patients. Rhoptries, micronemes, and dense granules, which are secretory organelles unique to Toxoplasma and other apicomplexan parasites, play critical roles in parasite growth and virulence. To understand how these organelles modulate infected host cells, we sought to identify host cell transcription factors triggered by their release. Early growth response 2 (EGR2) is a host cell transcription factor that is rapidly upregulated and activated in Toxoplasma-infected cells but not in cells infected with the closely related apicomplexan parasite Neospora caninum. EGR2 upregulation occurred only when live parasites were in direct contact with the host cell and not from exposure to cell extracts that contain dense granule or micronemal proteins. When microneme-mediated attachment was blocked by pretreating parasites with a calcium chelator, EGR2 expression was significantly reduced. In contrast, when host cells were infected with parasites in the presence of cytochalasin D, which allows rhoptry secretion but prevents parasite invasion, EGR2 was activated. Finally, we demonstrate that Toxoplasma activation of host p38 mitogen-activated protein kinase is necessary but not sufficient for EGR2 activation. Collectively, these data indicate that EGR2 is specifically upregulated by a parasite-derived secreted factor that is most likely a resident rhoptry protein.

Monocyte-mediated defense against microbial pathogens

Circulating blood monocytes supply peripheral tissues with macrophage and dendritic cell (DC) precursors and, in the setting of infection, also contribute directly to immune defense against microbial pathogens. In humans and mice, monocytes are divided into two major subsets that either specifically traffic into inflamed tissues or, in the absence of overt inflammation, constitutively maintain tissue macrophage/DC populations. Inflammatory monocytes respond rapidly to microbial stimuli by secreting cytokines and antimicrobial factors, express the CCR2 chemokine receptor, and traffic to sites of microbial infection in response to monocyte chemoattractant protein (MCP)-1 (CCL2) secretion. In murine models, CCR2-mediated monocyte recruitment is essential for defense against Listeria monocytogenes, Mycobacterium tuberculosis, Toxoplasma gondii, and Cryptococcus neoformans infection, implicating inflammatory monocytes in defense against bacterial, protozoal, and fungal pathogens. Recent studies indicate that inflammatory monocyte recruitment to sites of infection is complex, involving CCR2-mediated emigration of monocytes from the bone marrow into the bloodstream, followed by trafficking into infected tissues. The in vivo mechanisms that promote chemokine secretion, monocyte differentiation and trafficking, and finally monocyte-mediated microbial killing remain active and important areas of investigation.

Several transcription factors regulate COX-2 gene expression in pancreatic beta-cells

Cyclooxygenase-2 (COX-2) expression is associated with many aspects of physiological and pathological conditions, including pancreatic beta-cell dysfunction. Prostaglandin E2 (PGE2) production, as a consequence of COX-2 gene induction, has been reported to impair beta-cell function. The molecular mechanisms involved in the regulation of COX-2 gene expression are not fully understood. In this report, we used pancreatic beta-cells (RINm5F) to explore the potential transcription factors regulating COX-2 promoter activity. Using promoter screening method, we selected several transcription factors in our study. Through luciferase reporter studies, we found that these factors can regulate COX-2 promoter activity in RINm5F cells. Among these factors, cyclic AMP response-element binding protein (CREB), Ets family members Ets-1 and Elk-1 can positively regulate COX-2 promoter activity. On the contrary, signal transducer and activator of transcription 1 (STAT1) plays a negative role on COX-2 promoter. Our findings will be helpful for better understanding the transcriptional regulation of COX-2 in pancreatic beta-cells. Moreover, these transcriptional regulators of COX-2 expression will be potential targets for the prevention of beta-cell damage mediated by PGE2.