Critical role of toll-like receptor 9 in morphine and Mycobacterium tuberculosis-Induced apoptosis in mice

Immunomodulatory properties of morphine and the hypothesised role of long-term opioid use in the immunopathogenesis of tuberculosis

Epidemiological studies have shown high tuberculosis (TB) prevalence among chronic opioid users. Opioid receptors are found on multiple immune cells and immunomodulatory properties of opioids could be a contributory factor for ensuing immunosuppression and development or reactivation of TB. Toll-like receptors (TLR) mediate an immune response against microbial pathogens, including Mycobacterium tuberculosis. Mycobacterial antigens and opioids co-stimulate TLRs 2/4/9 in immune cells, with resulting receptor cross-talk via multiple cytosolic secondary messengers, leading to significant immunomodulatory downstream effects. Blockade of specific immune pathways involved in the host defence against TB by morphine may play a critical role in causing tuberculosis among chronic morphine users despite multiple confounding factors such as socioeconomic deprivation, Human immunodeficiency virus co-infection and malnutrition. In this review, we map out immune pathways involved when immune cells are co-stimulated with mycobacterial antigens and morphine to explore a potential immunopathological basis for TB amongst long-term opioid users.

Toll-Like Receptor 9 Signaling Pathway Contributes to Intestinal Mucosal Barrier Injury in Mice With Severe Acute Pancreatitis

OBJECTIVES

The purpose of this study was to investigate the role and mechanism of toll-like receptor 9 (TLR9) in intestinal mucosal barrier injury in mice with severe acute pancreatitis (SAP).

METHODS

The mice were randomly divided into 3 groups: control group, SAP group, and TLR9 antagonist-treated group. The expression of tumor necrosis factor-α, interleukin-1β, interleukin-6, diamine oxidase, and endotoxin core antibodies were detected by enzyme-linked immunosorbent assay. The protein expression of zonula occluden-1 (ZO)-1, occludin, TLR9, myeloid differentiation factor 88 (MyD88), tumor necrosis factor receptor-associated factor 6 (TRAF6), p-nuclear factor (NF)-κB p65, and NF-κB p65 were detected by Western blot. TdT-mediated dUTP nick-end labeling staining was used for detecting intestinal epithelial cell apoptosis.

RESULTS

The expression of TLR9 and its related pathway proteins MyD88, TRAF6, and p-NF-κB p65 in the intestinal tract of SAP mice were significantly increased compared with that of control mice. Inhibition of the TLR9 expression could reduce the level of serum proinflammatory cytokines, reduce the apoptosis of intestinal epithelial cells, improve intestinal permeability, and ultimately reduce the damage of intestinal mucosal barrier function in SAP.

CONCLUSIONS

Toll-like receptor 9/MyD88/TRAF6/NF-κB signaling pathway plays an important role in intestinal mucosal barrier injury of SAP.

Nontuberculous Mycobacteria, Macrophages, and Host Innate Immune Response

Although nontuberculous mycobacteria (NTM) are considered opportunistic infections, incidence and prevalence of NTM infection are increasing worldwide becoming a major public health threat. Innate immunity plays an essential role in mediating the initial host response against these intracellular bacteria. Specifically, macrophages phagocytose and eliminate NTM and act as antigen-presenting cells, which trigger downstream activation of cellular and humoral adaptive immune responses. Identification of macrophage receptors, mycobacterial ligands, phagosome maturation, autophagy/necrosis, and escape mechanisms are important components of this immunity network. The role of the macrophage in mycobacterial disease has mainly been studied in tuberculosis (TB), but limited information exists on its role in NTM. In this review, we focus on NTM immunity, the role of macrophages, and host interaction in NTM infection.

Impact of Opioid Use in Hematological Malignancies: Clinical, Immunological and Concomitant Aspects

Opioid agents play a unique role in pain and symptom management for cancer patients. Research shows that opiate use, especially when associated with underlying cancer, has significant effects on hematological parameters. These changes may lead to greater risk for immunosuppression, tumor growth and progression of metastatic processes. The aim of this review is to explore the effects of opiates on various metabolic and biological processes, as well as the hematopoietic system, especially in cancer patients. Our findings demonstrate that the tumor-promoting effects of opiates remain contradictory, as both growth-promoting and anti-tumor effects have been observed. However, available data suggest that opiates can facilitate the proliferation and migration of tumor cells, and understanding of this process on cancer treatment is tremendously important.

Association between toll-like receptors 9 (TLR9) gene polymorphism and risk of pulmonary tuberculosis: meta-analysis

BACKGROUND

Previous studies indicated that the single nucleotide polymorphisms (SNPs) in TLR9 gene might be associated with Tuberculosis (TB) risk. However, the results are inconsistent and inconclusive.

METHODS

1745 articles from four databases were involved in our study. A meta-analysis on the associations between the seven polymorphisms and TB risk was carried out by comparison using different genetic models.

RESULTS

In this systematic review 8 studies from seven English articles were analyzed. Our results showed that rs352139 is significantly associated with TB risk (AA vs. AG, OR 0.77, 95% CI 0.65-0.92, P = 0.004). In the ethnic subgroup analysis, Indonesians with AA genotype had a decreased susceptibility while Mexicans with GG allele had an increased risk.

CONCLUSIONS

The meta-analysis indicated that rs352139 polymorphism might be associated with decreased TB risk in Indonesians whereas increased risk in Mexicans. Whether the observed association was due to causal effect needs to be further studied.

The role of toll-like receptor 9 in chronic stress-induced apoptosis in macrophage

Emerging evidence implied that chronic stress has been exerting detrimental impact on immune system functions in both humans and animals. Toll-like receptors (TLRs) have been shown to play an essential role in modulating immune responses and cell survival. We have recently shown that TLR9 deficiency protects against lymphocyte apoptosis induced by chronic stress. However, the exact role of TLR9 in stress-mediated change of macrophage function remains unclear. The results of the current study showed that when BALB/c mice were treated with restraint stress (12 h daily for 2 days), the number of macrophages recruited to the peritoneal cavity was obviously increased. Results also demonstrated that the sustained effects of stress elevated cytokine IL-1β, TNF-α and IL-10 production yet diminished IFN-γ production from macrophage, which led to apoptotic cell death. However, TLR9 deficiency prevented the chronic stress-mediated accumulation of macrophages. In addition, knocking out TLR9 significantly abolished the chronic stress-induced imbalance of cytokine levels and apoptosis in macrophage. TLR9 deficiency was also found to reverse elevation of plasma IL-1β, IL-10 and IL-17 levels and decrease of plasma IFN-γ level under the condition of chronic stress. These results indicated that TLR9-mediated macrophage responses were required for chronic stress-induced immunosuppression. Further exploration showed that TLR9 deficiency prevented the increment of p38 MAPK phosphorylation and reduction of Akt/Gsk-3β phosphorylation; TLR9 deficiency also attenuated the release of mitochondrial cytochrome c into cytoplasm, caused upregulation of Bcl-2/Bax protein ratio, downregulation of cleavage of caspase-3 and PARP, as well as decreased TUNEL-positive cells in macrophage of stressed mice. Collectively, our studies demonstrated that deficiency of TLR9 maintained macrophage function by modulating macrophage accumulation and attenuating macrophage apoptosis, thus preventing immunosuppression in restraint-stressed mice.

Inhibition of Toll-like receptor 9 attenuates sepsis-induced mortality through suppressing excessive inflammatory response

Sepsis, a major clinical problem with high morbidity and mortality, is caused by overwhelming systemic host-inflammatory response. Toll-like receptors (TLRs) play a fundamental role in induction of hyperinflammation and tissue damage in sepsis. In this study, we demonstrate a protective role of TLR9 inhibition against the dysregulated inflammatory response and tissue injury in sepsis. TLR9 deficiency decreased the mortality of mice following cecal ligation and puncture (CLP)-induced sepsis. TLR9 knockout mice showed dampened p38 activation and augmented Akt phosphorylation in the spleen, lung and liver. In addition, TLR9 deficiency decreased the levels of inflammatory cytokines and attenuated splenic apoptosis after CLP. These results indicate that TLR9 inhibition might offer a novel therapeutic strategy for the management of sepsis.

Active and latent tuberculosis among HIV-positive injecting drug users in Indonesia

Introduction

Injecting drug use (IDU) is associated with tuberculosis but few data are available from low-income settings. We examined IDU in relation to active and latent tuberculosis (LTBI) among HIV-positive individuals in Indonesia, which has a high burden of tuberculosis and a rapidly growing HIV epidemic strongly driven by IDU.

Methods

Active tuberculosis was measured prospectively among 1900 consecutive antiretroviral treatment (ART)-naïve adult patients entering care in a clinic in West Java. Prevalence of LTBI was determined cross-sectionally in a subset of 518 ART-experienced patients using an interferon-gamma release assay.

Results

Patients with a history of IDU (53.1%) more often reported a history of tuberculosis treatment (34.8% vs. 21.9%, p<0.001), more often received tuberculosis treatment during follow-up (adjusted HR=1.71; 95% CI: 1.25–2.35) and more often had bacteriologically confirmed tuberculosis (OR=1.67; 95% CI: 0.94–2.96). LTBI was equally prevalent among people with and without a history of IDU (29.1 vs. 30.4%, NS). The risk estimates did not change after adjustment for CD4 cell count or ART.

Conclusions

HIV-positive individuals with a history of IDU in Indonesia have more active tuberculosis, with similar rates of LTBI. Within the HIV clinic, LTBI screening and isoniazid preventive therapy may be prioritized to patients with a history of IDU.

Activated microglia contribute to neuronal apoptosis in Toxoplasmic encephalitis

BACKGROUND

A plethora of evidence shows that activated microglia play a critical role in the pathogenesis of the central nervous system (CNS). Toxoplasmic encephalitis (TE) frequently occurs in HIV/AIDS patients. However, knowledge remains limited on the contributions of activated microglia to the pathogenesis of TE.

METHODS

A murine model of reactivated encephalitis was generated in a latent infection with Toxoplasma gondii induced by cyclophosphamide. The neuronal apoptosis in the CNS and the profile of pro-inflammatory cytokines were assayed in both in vitro and in vivo experiments.

RESULTS

Microglial cells were found to be activated in the cortex and hippocampus in the brain tissues of mice. The in vivo expression of interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase (iNOS) were up-regulated in TE mice, and accordingly, the neuronal apoptosis was significantly increased. The results were positively correlated with those of the in vitro experiments. Additionally,apoptosis of the mouse neuroblastoma type Neuro2a (N2a) remarkably increased when the N2a was co-cultured in transwell with microglial cells and Toxoplasma tachyzoites. Both in vivo and in vitro experiments showed that minocycline (a microglia inhibitor) treatment notably reduced microglial activation and neuronal apoptosis.

CONCLUSIONS

Activated microglia contribute to neuronal apoptosis in TE and inhibition of microglia activation might represent a novel therapeutic strategy of TE.

Toll-like receptor 9 is required for chronic stress-induced immune suppression

OBJECTIVES

Mental and physical stress can suppress the immune system in both humans and animals. The mechanism by which stress affects immune responses, however, remains poorly defined. Toll-like receptors (TLRs) play a key role in modulating immune responses and cell survival. The mechanisms by which TLRs modulate chronic stress are largely unexplored.

METHODS

Six- to 8-week-old male mice were subjected to chronic 12-hour daily physical restraint stress. Apoptotic cells were determined by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) assay. We examined cytokine levels by enzyme-linked immunosorbent Assay (ELISA). The expression of CYP11A1 was determined by quantitative real-time RT-PCR.

RESULTS

TLR9-deficient mice were resistant to chronic stress-induced lymphocyte apoptosis. In addition, in TLR9 knockout (KO) mice, chronic stress-induced upregulation of corticosterone levels was significantly decreased. Notably, lymphocytes from both TLR9 KO and wild-type mice were similarly sensitive to corticosteroid-induced cell apoptosis. Moreover, TLR9 deficiency blocked the chronic stress-induced imbalance in T helper (Th) 1 and Th2 cytokine levels.

CONCLUSION

Taken together, our findings reveal that TLR9 plays an essential role in chronic stress-induced immune suppression.

Hydroxysafflor yellow A protects against cerebral ischemia-reperfusion injury by anti-apoptotic effect through PI3K/Akt/GSK3β pathway in rat

Hydroxysafflor yellow A (HSYA) is the major active chemical component of the flower of the safflower plant, Carthamus tinctorius L. Previously, its neuroprotection against cerebral ischemia-reperfusion (I/R) injury was reported by anti-oxidant action and suppression of thrombin generation. Here, we investigate the role of HSYA in cerebral I/R-mediated apoptosis and possible signaling pathways. Male Wistar rats were subjected to transient middle cerebral artery occlusion for 2 h, followed by 24 h reperfusion. HSYA was administered via tail-vein injection just 15 min after occlusion. The number of apoptotic cells was measured by TUNEL assay, apoptosis-related proteins Bcl-2, Bax and the phosphorylation levels of Akt and GSK3β in ischemic penumbra were assayed by western blot. The results showed that administration of HSYA at the doses of 4 and 8 mg/kg significantly inhibited the apoptosis by decreasing the number of apoptotic cells and increasing the Bcl-2/Bax ratio in rats subjected to I/R injury. Simultaneously, HSYA treatment markedly increased the phosphorylations of Akt and GSK3β. Blockade of PI3K activity by wortmannin dramatically abolished its anti-apoptotic effect and lowered both Akt and GSK3β phosphorylation levels. Taken together, these results suggest that HSYA protects against cerebral I/R injury partly by reducing apoptosis via PI3K/Akt/GSK3β signaling pathway.

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).

Toll-like receptor 9 is required for opioid-induced microglia apoptosis

Opioids have been widely applied in clinics as one of the most potent pain relievers for centuries, but their abuse has deleterious physiological effects beyond addiction. However, the underlying mechanism by which microglia in response to opioids remains largely unknown. Here we show that morphine induces the expression of Toll-like receptor 9 (TLR9), a key mediator of innate immunity and inflammation. Interestingly, TLR9 deficiency significantly inhibited morphine-induced apoptosis in microglia. Similar results were obtained when endogenous TLR9 expression was suppressed by the TLR9 inhibitor CpGODN. Inhibition of p38 MAPK by its specific inhibitor SB203580 attenuated morphine-induced microglia apoptosis in wild type microglia. Morphine caused a dramatic decrease in Bcl-2 level but increase in Bax level in wild type microglia, but not in TLR9 deficient microglia. In addition, morphine treatment failed to induce an increased levels of phosphorylated p38 MAPK and MAP kinase kinase 3/6 (MKK3/6), the upstream MAPK kinase of p38 MAPK, in either TLR9 deficient or µ-opioid receptor (µOR) deficient primary microglia, suggesting an involvement of MAPK and µOR in morphine-mediated TLR9 signaling. Moreover, morphine-induced TLR9 expression and microglia apoptosis appears to require μOR. Collectively, these results reveal that opioids prime microglia to undergo apoptosis through TLR9 and µOR as well. Taken together, our data suggest that inhibition of TLR9 and/or blockage of µOR is capable of preventing opioid-induced brain damage.

Toll-like receptor 9 is required for full host resistance to Mycobacterium avium infection but plays no role in induction of Th1 responses

To investigate the role of Toll-like receptor 9 (TLR9) in innate immunity to Mycobacterium avium, TLR9, TLR2, and MyD88 knockout (KO) mice were infected with this bacterium. Bacterial burdens were higher in the spleens, livers, and lungs of infected TLR9 KO mice than in those of C57BL/6 mice, indicating that TLR9 is required for efficient control of M. avium infection. However, TLR9 KO or TLR2 KO spleen cells displayed normal M. avium-induced tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ) responses. This finding was confirmed by determining the number of splenic CD4(+) T cells producing IFN-γ by flow cytometry. Furthermore, TLR2 and MyD88, but not TLR9, played a major role in interleukin-12 and TNF-α production by M. avium-infected macrophages and dendritic cells (DCs). We also found that major histocompatibility complex class II molecule expression on DCs is regulated by TLR2 and MyD88 signaling but not by TLR9. Finally, lack of TLR9, TLR2, or MyD88 reduced the numbers of macrophages, epithelioid cells, and lymphocytes in M. avium-induced granulomas but only MyD88 deficiency affected the number of liver granulomas. In summary, our data demonstrated that the involvement of TLR9 in the control of M. avium infection is not related to the induction of Th1 responses.