Plasma levels of trace elements have an implication on interferon treatment of children with chronic hepatitis B infection

Divalent Metal Uptake and the Role of ZIP8 in Host Defense Against Pathogens

Manganese (Mn) and Zinc (Zn) are essential micronutrients whose concentration and location within cells are tightly regulated at the onset of infection. Two families of Zn transporters (ZIPs and ZnTs) are largely responsible for regulation of cytosolic Zn levels and to a certain extent, Mn levels, although much less is known regarding Mn. The capacity of pathogens to persevere also depends on access to micronutrients, yet a fundamental gap in knowledge remains regarding the importance of metal exchange at the host interface, often referred to as nutritional immunity. ZIP8, one of 14 ZIPs, is a pivotal importer of both Zn and Mn, yet much remains to be known. Dietary Zn deficiency is common and commonly occurring polymorphic variants of ZIP8 that decrease cellular metal uptake (Zn and Mn), are associated with increased susceptibility to infection. Strikingly, ZIP8 is the only Zn transporter that is highly induced following bacterial exposure in key immune cells involved with host defense against leading pathogens. We postulate that mobilization of Zn and Mn into key cells orchestrates the innate immune response through regulation of fundamental defense mechanisms that include phagocytosis, signal transduction, and production of soluble host defense factors including cytokines and chemokines. New evidence also suggests that host metal uptake may have long-term consequences by influencing the adaptive immune response. Given that activation of ZIP8 expression by pathogens has been shown to influence parenchymal, myeloid, and lymphoid cells, the impact applies to all mucosal surfaces and tissue compartments that are vulnerable to infection. We also predict that perturbations in metal homeostasis, either genetic- or dietary-induced, has the potential to impact bacterial communities in the host thereby adversely impacting microbiome composition. This review will focus on Zn and Mn transport via ZIP8, and how this vital metal transporter serves as a "go to" conductor of metal uptake that bolsters host defense against pathogens. We will also leverage past studies to underscore areas for future research to better understand the Zn-, Mn- and ZIP8-dependent host response to infection to foster new micronutrient-based intervention strategies to improve our ability to prevent or treat commonly occurring infectious disease.

Selenium Status in Patients with Chronic Liver Disease: A Systematic Review and Meta-Analysis

Background: The potential role of selenium in preventing chronic liver diseases remains controversial. This meta-analysis aimed to summarize the available evidence from observational studies and intervention trials that had evaluated the associations between body selenium status and chronic liver diseases. Methods: We comprehensively searched MEDLINE, Embase, Web of Science, and Cochrane Library from inception to April 2021. The study protocol was registered at PROSPERO (CRD42020210144). Relative risks (RR) for the highest versus the lowest level of selenium and standard mean differences (SMD) with 95% confidence intervals (CI) were pooled using random-effects models. Heterogeneity and publication bias were evaluated using the I² statistic and Egger’s regression test, respectively. Results: There were 50 studies with 9875 cases and 12975 population controls in the final analysis. Patients with hepatitis (SMD = −1.78, 95% CI: −2.22 to −1.34), liver cirrhosis (SMD = −2.06, 95% CI: −2.48 to −1.63), and liver cancer (SMD = −2.71, 95% CI: −3.31 to −2.11) had significantly lower selenium levels than controls, whereas there was no significant difference in patients with fatty liver diseases (SMD = 1.06, 95% CI: −1.78 to 3.89). Moreover, the meta-analysis showed that a higher selenium level was significantly associated with a 41% decrease in the incidence of significant advanced chronic liver diseases (RR = 0.59, 95% CI: 0.49 to 0.72). Conclusion: Our meta-analysis suggested that both body selenium status and selenium intake were negatively associated with hepatitis, cirrhosis, and liver cancer. However, the associations for fatty liver diseases were conflicting and need to be established in prospective trials.

Manganese homeostasis at the host-pathogen interface and in the host immune system

Manganese serves as an indispensable catalytic center and the structural core of various enzymes that participate in a plethora of biological processes, including oxidative phosphorylation, glycosylation, and signal transduction. In pathogenic microorganisms, manganese is required for survival by maintaining basic biochemical activity and virulence; in contrast, the host utilizes a process known as nutritional immunity to sequester manganese from invading pathogens. Recent epidemiological and animal studies have shown that manganese increases the immune response in a wide range of vertebrates, including humans, rodents, birds, and fish. On the other hand, excess manganese can cause neurotoxicity and other detrimental effects. Here, we review recent data illustrating the essential role of manganese homeostasis at the host-pathogen interface and in the host immune system. We also discuss the accumulating body of evidence that manganese modulates various signaling pathways in immune processes. Finally, we discuss the key molecular players involved in manganese's immune regulatory function, as well as the clinical implications with respect to cancer immunotherapy.

Selenium, Selenoproteins and Viral Infection

Reactive oxygen species (ROS) are frequently produced during viral infections. Generation of these ROS can be both beneficial and detrimental for many cellular functions. When overwhelming the antioxidant defense system, the excess of ROS induces oxidative stress. Viral infections lead to diseases characterized by a broad spectrum of clinical symptoms, with oxidative stress being one of their hallmarks. In many cases, ROS can, in turn, enhance viral replication leading to an amplification loop. Another important parameter for viral replication and pathogenicity is the nutritional status of the host. Viral infection simultaneously increases the demand for micronutrients and causes their loss, which leads to a deficiency that can be compensated by micronutrient supplementation. Among the nutrients implicated in viral infection, selenium (Se) has an important role in antioxidant defense, redox signaling and redox homeostasis. Most of biological activities of selenium is performed through its incorporation as a rare amino acid selenocysteine in the essential family of selenoproteins. Selenium deficiency, which is the main regulator of selenoprotein expression, has been associated with the pathogenicity of several viruses. In addition, several selenoprotein members, including glutathione peroxidases (GPX), thioredoxin reductases (TXNRD) seemed important in different models of viral replication. Finally, the formal identification of viral selenoproteins in the genome of molluscum contagiosum and fowlpox viruses demonstrated the importance of selenoproteins in viral cycle.

Changes in Liver Tissue Trace Element Concentrations During Hepatitis B Viral Infection Treatment

Approximately 350-400 million people in the world have Hbs Ag (hepatitis B virus surface antigen) positivity. In the international guidelines, the permanent suppression of replication in chronic hepatitis B virus (HBV) infection therapy is reported as the primary therapeutic goal. Trace elements play a key role in liver diseases. The aim of our study is to determine some trace element concentrations in the liver during HBV treatment periods. The measurement of 11 trace elements (manganese, lead, nickel, chromium, cadmium, iron, copper, zinc, silver, cobalt, and aluminum) was carried out by the method of inductively coupled plasma mass spectrometry in liver biopsy materials (before starting treatment and at the sixth month of the treatment period). There was an increase in zinc and copper concentrations in liver materials at the sixth month of treatment compared to the pre-treatment values (the median zinc value was 48.05 μg/g before treatment and 74.9 μg/g at 6 months after initial treatment, p = 0.035; median copper was 2.82 μg/g before treatment and 5.31 μg/g after 6 months, p = 0.002). General estimations indicated that zinc (p = 0.002), iron (p = 0.0244), copper (p = 0.0003), and aluminum (p = 0.0239) values may be effective in HAI (histological activity index) changes. Only iron levels could be at a very low level effective on the changes caused by fibrosis (p = 0.0002). Liver tissue zinc and copper levels increased in parallel with the improvement of inflammation in antiviral-treated HBV patients. In addition, the levels of zinc and copper in the liver tissue can be useful markers for liver tissue damage detection.

Role of divalent metals in infectious disease susceptibility and outcome

BACKGROUND

Divalent metals play important roles in maintaining metabolism and cellular growth of both eukaryotic hosts and invading microbes. Both metal deficiency and overload can result in abnormal cellular function or damage. Given its central role in host-pathogen interactions, subtle alterations of divalent metal homeostasis can occur in the course of infectious diseases which aim, from the host perspective, either to reduce the availability of respective metals to microbes or to use toxic metal accumulation to eliminate pathogens.

AIMS

To provide the reader with background information and clinical data on divalent metal homeostasis in host-pathogen interactions, how this affects the course of infectious disease and whether correction of metal disturbances has shown benefit in infections.

SOURCES

An in-depth analysis of PubMed articles related to the topic of this review published in English between 1970 and 2016 was performed.

CONTENT

From the microbial perspective, divalent metals are essential for growth and pathogenicity and to mount effective protection against antimicrobial host responses, including toxic radical formation. Microbes have evolved multiple strategies to control their access to divalent metals. From the clinical perspective, alterations of divalent metal levels may result in increased or decreased susceptibility to infection and often occur in response to infections. However, keeping in mind the strategies underlying such alterations, for which the term 'nutritional immunity' was coined, the uncritical correction of such divalent metal imbalances may cause harm to patients. This review addresses the role of the divalent metals iron, selenium, zinc, manganese and copper in infectious diseases from a mechanistic and clinical perspective.

IMPLICATIONS

We point out areas of research needed to expand our limited knowledge, hoping to improve the clinical management of patients with infections and to identify promising new targets for treatment by modulation of host or microbe divalent metal metabolism.

Interferon-alpha-2a and zinc combination therapy in children with chronic hepatitis B infection

Zinc has been reported to enhance the response to interferon (IFN) or PEG-IFN plus ribavirin therapy, improve liver function, and ameliorate hematologic side effects in patients with chronic hepatitis C. However, the role of zinc supplementation during IFN therapy in chronic hepatitis B infection (CHB) remains unclear. We therefore aimed to report the results of zinc and IFN-alpha-2a therapy in children with CHB. Twenty-two naive, HBeAg-positive children (mean age 10.4 ± 4.4 years) received IFN-α2a (9 MU/m(2) sc) for 6 months plus peroral zinc (7.5 mg/day for <10 years and 10 mg/day for >10 years) for 12 months. Serum zinc, alanine aminotransferase (ALT), complete blood count, hepatitis B virus DNA (HBV DNA), and serological markers were measured. Histological (HR) and sustained response (SR) were evaluated at 6 months after completion of therapy. Normalization of ALT, HBeAg seroconversion, and HBV DNA < 10,000 copies/ml were considered as SR. HR was defined as decrease in Knodell histological activity index (HAI) score by at least 2 points compared to baseline. End of therapy ALT level and log HBV DNA were significantly lower than pretherapy levels (p = 0.001 and p = 0.001, respectively), while zinc level was not different. Portal inflammation score significantly decreased after therapy (p = 0.043), however, total HAI and other HAI components were not different. SR and HR were 25% and 52.9%. In conclusion as a first study investigating the effect of zinc and IFN combination therapy in children with CHB, SR and HR rates were not better than previously reported monotherapy or combination therapies.