Levels of nitric oxide, gamma interferon and interleukin-12 in AIDS patients with toxoplasmic encephalitis

Cytokines and chemokines profile in encephalitis patients: A meta-analysis

BACKGROUND

Encephalitis is caused by autoimmune or infectious agents marked by brain inflammation. Investigations have reported altered concentrations of the cytokines in encephalitis. This study was conducted to determine the relationship between encephalitis and alterations of cytokine levels in cerebrospinal fluid (CSF) and serum.

METHODS

We found possibly suitable studies by searching PubMed, Embase, Scopus, and Web of Science, systematically from inception to August 2021. 23 articles were included in the meta-analysis. To investigate sources of heterogeneity, subgroup analysis and sensitivity analysis were conducted. The protocol of the study has been registered in PROSPERO with a registration ID of CRD42021289298.

RESULTS

A total of 23 met our eligibility criteria to be included in the meta-analysis. A total of 12 cytokines were included in the meta-analysis of CSF concentration. Moreover, 5 cytokines were also included in the serum/plasma concentration meta-analysis. According to the analyses, patients with encephalitis had higher CSF amounts of IL-6, IL-8, IL-10, CXCL10, and TNF-α than healthy controls. The alteration in the concentration of IL-2, IL-4, IL-17, CCL2, CXCL9, CXCL13, and IFN-γ was not significant. In addition, the serum/plasma levels of the TNF-α were increased in encephalitis patients, but serum/plasma concentration of the IL-6, IL-10, CXCL10, and CXCL13 remained unchanged.

CONCLUSIONS

This meta-analysis provides evidence for higher CSF concentrations of IL-6, IL-8, IL-10, CXCL10, and TNF-α in encephalitis patients compared to controls. The diagnostic and prognostic value of these cytokines and chemokines should be investigated in future studies.

Murine Model of Primary Acquired Ocular Toxoplasmosis: Fluorescein Angiography and Multiplex Immune Mediator Profiles in the Aqueous Humor

Purpose

To establish a murine model of primary acquired ocular toxoplasmosis (OT) and to investigate the immune mediator profiles in the aqueous humor (AH).

Methods

C57BL/6 mice were perorally infected with Toxoplasma gondii. The ocular fundus was observed, and fluorescein angiography (FA) was performed. The AH, cerebrospinal fluid (CSF), and serum were collected before infection and at 28 days post-infection (dpi); the immune mediator levels in these samples were analyzed using multiplex bead assay.

Results

Fundus imaging revealed soft retinochoroidal lesions at 14 dpi; many of these lesions became harder by 28 dpi. FA abnormalities, such as leakage from retinal vessels and dilation and tortuosity of the retinal veins, were observed at 14 dpi. Nearly all these abnormalities resolved spontaneously at 28 dpi. In the AH, interferon-γ, interleukin (IL)-1α, IL-1β, IL-6, IL-10, IL-12(p40), IL-12(p70), CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1β, CCL5/RANTES, and CXCL1/KC levels increased after infection. All these molecules except IL-1α, IL-4, and IL-13 showed almost the same postinfection patterns in the CSF as they did in the AH. The tumor necrosis factor α, IL-4, and IL-5 levels in the AH and CSF of the T. gondii–infected mice were lower than those in the serum. The postinfection IL-1α, IL-6, CCL2/MCP-1, CCL4/MIP-1β, and granulocyte colony-stimulating factor levels in the AH were significantly higher than those in the CSF and serum.

Conclusions

A murine model of primary acquired OT induced via the natural infection route was established. This OT model allows detailed ophthalmologic, histopathologic, and immunologic evaluations of human OT. Investigation of AH immune modulators provides new insight into OT immunopathogenesis.

Nitrite as regulator of hypoxic signaling in mammalian physiology

In this review we consider the effects of endogenous and pharmacological levels of nitrite under conditions of hypoxia. In humans, the nitrite anion has long been considered as metastable intermediate in the oxidation of nitric oxide radicals to the stable metabolite nitrate. This oxidation cascade was thought to be irreversible under physiological conditions. However, a growing body of experimental observations attests that the presence of endogenous nitrite regulates a number of signaling events along the physiological and pathophysiological oxygen gradient. Hypoxic signaling events include vasodilation, modulation of mitochondrial respiration, and cytoprotection following ischemic insult. These phenomena are attributed to the reduction of nitrite anions to nitric oxide if local oxygen levels in tissues decrease. Recent research identified a growing list of enzymatic and nonenzymatic pathways for this endogenous reduction of nitrite. Additional direct signaling events not involving free nitric oxide are proposed. We here discuss the mechanisms and properties of these various pathways and the role played by the local concentration of free oxygen in the affected tissue.

Vascular oxidative stress and nitric oxide depletion in HIV-1 transgenic rats are reversed by glutathione restoration

Human immunodeficiency virus (HIV)-infected patients have a higher incidence of oxidative stress, endothelial dysfunction, and cardiovascular disease than uninfected individuals. Recent reports have demonstrated that viral proteins upregulate reactive oxygen species, which may contribute to elevated cardiovascular risk in HIV-1 patients. In this study we employed an HIV-1 transgenic rat model to investigate the physiological effects of viral protein expression on the vasculature. Markers of oxidative stress in wild-type and HIV-1 transgenic rats were measured using electron spin resonance, fluorescence microscopy, and various molecular techniques. Relaxation studies were completed on isolated aortic rings, and mRNA and protein were collected to measure changes in expression of nitric oxide (NO) and superoxide sources. HIV-1 transgenic rats displayed significantly less NO-hemoglobin, serum nitrite, serum S-nitrosothiols, aortic tissue NO, and impaired endothelium-dependent vasorelaxation than wild-type rats. NO reduction was not attributed to differences in endothelial NO synthase (eNOS) protein expression, eNOS-Ser1177 phosphorylation, or tetrahydrobiopterin availability. Aortas from HIV-1 transgenic rats had higher levels of superoxide and 3-nitrotyrosine but did not differ in expression of superoxide-generating sources NADPH oxidase or xanthine oxidase. However, transgenic aortas displayed decreased superoxide dismutase and glutathione. Administering the glutathione precursor procysteine decreased superoxide, restored aortic NO levels and NO-hemoglobin, and improved endothelium-dependent relaxation in HIV-1 transgenic rats. These results show that HIV-1 protein expression decreases NO and causes endothelial dysfunction. Diminished antioxidant capacity increases vascular superoxide levels, which reduce NO bioavailability and promote peroxynitrite generation. Restoring glutathione levels reverses HIV-1 protein-mediated effects on superoxide, NO, and vasorelaxation.

Differences among the three major strains of Toxoplasma gondii and their specific interactions with the infected host

Toxoplasma gondii is one of the most successful protozoan parasites owing to its ability to manipulate the immune system and establish a chronic infection. There are many T. gondii strains but the majority identified in Europe and North America falls into three distinct clonal lineages. Many studies have investigated the ability of T. gondii to manipulate its host but few have examined directly whether the three lineages differ in this ability.

Do neuroglobin and myoglobin protect Toxoplasma gondii from nitrosative stress?

Toxoplasma gondii is a Apicomplexa obligate intracellular protozoan parasite that infects up to a third of the world's population. In most humans infected with T. gondii, the disease toxoplasmosis is asymptomatic. However, T. gondii causes blindness, severe neurological disorders, hepatitis, and pneumonia in immunocompromised patients, and severe damage to the fetus. Here, we postulate that the colonization of the retina, heart, and skeletal muscle by T. gondii may reflect the role of neuroglobin (Ngb) and myoglobin (Mb) to protect the parasite from the toxoplasmacidal effects of nitric oxide (NO). This is based on the knowledge that Ngb and Mb catalyzes NO oxidation yielding the harmless nitrate. The postulated protective role of Ngb and Mb on the viability of T. gondii is reminiscent of that postulated for hemoglobin (Hb) and Mb in protecting intraerythrocytic Plasmodia and T. cruzi in cardiomyocytes, respectively, from the parasiticidal effect of NO. Therefore, undesirable pathogen protection by pseudo-enzymatic NO scavenging may represent a new unexpected function of members of the Hb superfamily.

Pathologic findings in the adrenal glands of autopsied patients with acquired immunodeficiency syndrome

A morphologic evaluation was carried out on adrenal glands from 128 autopsied patients with the acquired immunodeficiency syndrome (AIDS). The adrenal gland was compromised in 99.2% of the cases, with distinct pathological features and infectious agents. Inflammatory infiltrates were observed in 99.2% of the cases with a predominance of mononuclear cells in 97.4%, affecting mainly the medulla. Necrosis, fibrosis, hemorrhages and neoplasias were observed. We also described 3 (2.3%) cases of calcification located in the adrenal gland central vein (AGCV). This is seldom mentioned in the literature. Cytomegalovirus was the most frequent infectious agent, observed in 48.4% of cases. Balamuthia mandrillaris, a free living ameba, was found in one case affecting the entire gland. We also found a nest of Trypanosoma cruzi in the musculature of the AGCV. The presence of the nest of T cruzi in AGCV may play a role in the reactivation of this infection in immunosuppressed individuals. Pathologic processes and opportunistic infections may contribute to the alterations in the adrenal gland that lead to multiple organ failure observed in terminal AIDS patients.