Nicholas Van Wagoner

Interleukin-6 expression and regulation in astrocytes.

The physiological function of interleukin-6 (IL-6) within the central nervous system (CNS) is complex; IL-6 exerts neurotrophic and neuroprotective effects, and yet can also function as a mediator of inflammation, demyelination, and astrogliosis, depending on the cellular context. In the normal brain, IL-6 levels remain low. However, elevated expression occurs in injury, infection, stroke, and inflammation. Given the diverse biological functions of IL-6 and its expression in numerous CNS conditions, it is critical to understand its regulation in the brain in order to control its expression and ultimately its effects. Accumulating data demonstrate that the predominant CNS source of IL-6 is the activated astrocyte. Furthermore, a wide range of factors have been demonstrated to be involved in IL-6 regulation by astrocytes. In this review, we summarize information concerning IL-6 regulation in astrocytes, focusing on the role of proinflammatory factors, neurotransmitters, and second messengers.

Interleukin-6 (IL-6) Production by Astrocytes: Autocrine Regulation by IL-6 and the Soluble IL-6 Receptor

In the CNS, astrocytes are a major inducible source of interleukin-6 (IL-6). Although IL-6 has beneficial effects in the CNS because of its neurotrophic properties, its overexpression is generally detrimental, adding to the pathophysiology associated with CNS disorders. Many factors have been shown to induce IL-6 expression by astrocytes, particularly the cytokines tumor necrosis factor-α (TNF-α) and interleukin-1 β (IL-1β). However, the role of IL-6 in its own regulation in astrocytes has not been determined. In this study, we examined the influence of IL-6 alone or in combination with TNF-α or IL-1β on IL-6 expression. IL-6 alone had no effect on IL-6 expression; however, the addition of the soluble IL-6 receptor (sIL-6R) induced IL-6 transcripts. Addition of TNF-α or IL-1β plus IL-6/sIL-6R led to synergistic increases in IL-6 expression. This synergy also occurred in the absence of exogenously added IL-6, attributable to TNF-α- or IL-1β-induced endogenous IL-6 protein production. IL-6 upregulation seen in the presence of TNF-α or IL-1β plus IL-6/sIL-6R was transcriptional, based on nuclear run-on analysis. Experiments were extended to other IL-6 family members to determine their role in IL-6 regulation in astrocytes. Oncostatin M (OSM) induced IL-6 alone and synergized with TNF-α for enhanced expression. These results demonstrate that IL-6/sIL-6R and OSM play an important role in the regulation of IL-6 expression within the CNS, particularly in conjunction with the proinflammatory cytokines TNF-α and IL-1β.

ICAM-1-Induced Expression of Proinflammatory Cytokines in Astrocytes: Involvement of Extracellular Signal-Regulated Kinase and p38 Mitogen-Activated Protein Kinase Pathways

ICAM-1 is a transmembrane glycoprotein of the Ig superfamily involved in cell adhesion. ICAM-1 is aberrantly expressed by astrocytes in CNS pathologies such as multiple sclerosis, experimental allergic encephalomyelitis, and Alzheimer’s disease, suggesting a possible role for ICAM-1 in these disorders. ICAM-1 has been shown to be important for leukocyte diapedesis through brain microvessels and subsequent binding to astrocytes. However, other functional roles for ICAM-1 expression on astrocytes have not been well elucidated. Therefore, we investigated the intracellular signals generated upon ICAM-1 engagement on astrocytes. ICAM-1 ligation by a mAb to rat ICAM-1 induced mRNA expression of proinflammatory cytokines such as IL-1α, IL-1β, IL-6, and TNF-α. Examination of cytokine protein production revealed that ICAM-1 ligation results in IL-6 secretion by astrocytes, whereas IL-1β and IL-1α protein is expressed intracellularly in astrocytes. The involvement of mitogen-activated protein kinases (MAPKs) in ICAM-1-mediated cytokine expression in astrocytes was tested, as the MAPK extracellular signal-regulated kinase (ERK) was previously shown to be activated upon ICAM-1 engagement. Our results indicate that ERK1/ERK2, as well as p38 MAPK, are activated upon ligation of ICAM-1. Studies using pharmacological inhibitors demonstrate that both p38 MAPK and ERK1/2 are involved in ICAM-1-induced IL-6 expression, whereas only ERK1/2 is important for IL-1α and IL-1β expression. Our data support the role of ICAM-1 on astrocytes as an inflammatory mediator in the CNS and also uncover a novel signal transduction pathway through p38 MAPK upon ICAM-1 ligation.

Oncostatin M regulation of interleukin-6 expression in astrocytes: biphasic regulation involving the mitogen-activated protein kinases ERK1/2 and p38.

Oncostatin M (OSM) is a member of the interleukin (IL)‐6 family of cytokines and has both pro‐ and anti‐inflammatory properties. Of interest, OSM has functional effects within the CNS. We have shown recently that OSM can modulate expression of the cytokine IL‐6 in astrocytes. Herein we characterize the molecular mechanisms and signaling cascades involved in this response. OSM induces IL‐6 protein expression in a dose‐ and time‐dependent manner in astrocytes. In addition, OSM can synergize with the cytokines tumor necrosis factor‐α, IL‐1β, and transforming growth factor‐β for enhanced IL‐6 expression. Using neutralizing antibodies to gp 130, the OSM receptor (OSMR), and the leukemia inhibitory factor receptor (LIFR), we document that OSM exclusively uses the OSMR/gp 130 heterodimer in signaling events, rather than the LIFR/gp 130 heterodimer. Kinetic analysis of OSM‐induced IL‐6 mRNA reveals two up‐regulatory events. The first, peaking at 1 h, is transient, does not require protein synthesis, and is regulated at the transcriptional level. The second, peaking between 6 and 8 h, is prolonged and sensitive to puromycin, suggesting a requirement for de novo protein synthesis, and also is transcriptionally regulated. OSM‐induced IL‐6 mRNA and protein expression is inhibited by the mitogen‐activated protein kinase (MAPK) inhibitors U0126 and SB202190, suggesting a requirement for the MAPKs ERK1/2 and p38 in this response. Finally, we show that the MAPKs ERK1/2 and p38 are activated by OSM in astrocytes and that this activation is reduced by the MAPK inhibitors. These data demonstrate that OSM induces IL‐6 expression in astrocytes and that the MAPKs ERK1/2 and p38 participate in this response.

Fas engagement increases expression of interleukin-6 in human glioma cells.

Although Fas (APO-1/CD95) is expressed ubiquitously and induces cell death, it is also known to mediate other responses such as inflammation and angiogenesis in vivo. Previously, we have reported that Fas ligation induces selective expression of chemokines (IL-8 and MCP-1) in human astroglioma cells in vitro. In this study, we investigated whether Fas ligation can induce expression of other cytokines. Expression of IL-1α, IL-1β, IL-6, IL-10, IL-12, IFN-β, IFN-γ, LT-β, TGF-β, TNF-α and TNF-β mRNA levels in CRT-MG human astroglioma cells upon Fas ligation was investigated using RNase protection assay (RPA). We found that IL-6 mRNA is selectively induced upon Fas ligation, and IL-6 mRNA and protein expression was further investigated using single probe RPA and ELISA. To investigate the in vivo expression of IL-6, human brain specimens were homogenized and ELISA was performed for IL-6 expression. Herein, we demonstrate that: (1) Among these cytokines, only IL-6 was induced upon Fas ligation in a dose- and time-dependent manner; (2) A selective p38 MAP kinase inhibitor, SB202190, and a MEK inhibitor, U0126, suppressed induction of IL-6 mRNA and protein expression by Fas ligation; and (3) Glioblastoma multiforme samples (n = 11) contain significantly higher levels of IL-6 compared to those of control brains (n = 5), which correlate with increased levels of Fas. These results suggest that the Fas–FasL system may play a role in the regulation of tumor growth and survival by inducing the pleiotropic cytokine IL-6.

Gain-of-function signal transducer and activator of transcription 1 (STAT1) mutation-related primary immunodeficiency is associated with disseminated mucormycosis.

We identified a novel gain of function mutation in STAT1 in a patient with disseminated Apophysomyces trapeziformis infection who had never had mucocutaneous candidiasis or autoimmunity. To our knowledge this is the first report of a genetic predisposition associated with mucormycosis.

Nucleoside reverse-transcriptase inhibitor dosing errors in an outpatient HIV clinic in the electronic medical record era.

Information on antiretroviral dosing errors among health care providers for outpatient human immunodeficiency virus (HIV)-infected patients is lacking. We evaluated factors associated with nucleoside reverse-transcriptase inhibitor dosing errors in a university-based HIV clinic using an electronic medical record. Overall, older age, minority race or ethnicity, and didanosine use were related to such errors. Impaired renal function was more common in older patients and racial or ethnic minorities and, in conjunction with fixed-dose combination drugs, contributed to the higher rates of errors in nucleoside reverse-transcriptase inhibitor dosing. Understanding the factors related to nucleoside reverse-transcriptase inhibitor dosing errors is an important step in the building of preventive tools.

Church Attendance in Men Who Have Sex With Men Diagnosed With HIV Is Associated With Later Presentation for HIV Care

We demonstrate an interdependent relationship between sexual behavior and church attendance on timing of human immunodeficiency virus (HIV) diagnosis and presentation for care. Men who have sex with men (MSM) and who attend church are more likely to present with lower CD4(+) T-lymphocyte counts than MSM who do not attend church.

Herpes Diagnostic Tests and Their Use

Genital Herpes is common, causes a broad spectrum of clinical disease, and enhances susceptibility to other sexually transmitted infections, including HIV. Accurate diagnosis of Herpes Simplex Virus infection is important in surveillance, diagnosis and management, screening, and quality assurance. We have reviewed currently available herpes diagnostics and their appropriate use.

Herpes simplex virus in African American heterosexual males: the roles of age and male circumcision.

Background: Male circumcision is protective against human immunodeficiency virus (HIV) and select other STIs. The protective role of male circumcision in genital herpes simplex virus (HSV) infection and disease, however, remains controversial. Methods: We evaluated data from a sample of heterosexual black men attending a sexually transmitted diseases clinic to determine if circumcision status influenced HSV-1 and HSV-2 seroprevalence, clinical genital disease, or asymptomatic shedding. Consenting participants answered questionnaires detailing sexual history, then underwent a focused physical examination, serological testing for HSV-1 and HSV-2, and collection of genital swabs for virus detection. Univariate and multivariate analyses were performed to assess the relationship of circumcision status to HSV seroprevalence. Results: Of 460 men, 335 (73%) were circumcised and 125 (27%) were not circumcised; 61% were HSV-1 positive and 46% were HSV-2 positive. HSV-2 seroprevalence did not significantly differ between circumcised and uncircumcised men. However, uncircumcised men had a significantly higher HSV-1 seroprevalence than circumcised men (OR: 1.85; CI: 1.15–2.96). This difference in seroprevalence occurred only in men between 18 and 25 years of age (OR: 2.83; CI: 1.38–5.83) with men over 26 years of age having similar HSV-1 seroprevalence. Lack of circumcision remained independently associated with higher HSV-1 seroprevalence after adjusting for age, years since sexual debut, and lifetime number of sexual partners. For both groups, 20% of men had genital lesions on physical examination. Of circumcised and uncircumcised men with genital lesions, 33% and 31% were actively shedding HSV-1 or HSV-2 from lesions, respectively. Asymptomatic HSV shedding was observed in 12 participants, all of whom were circumcised. Conclusions: Lack of male circumcision is associated with higher HSV-1, but not HSV-2, seroprevalence in young black heterosexual men.