Differential regulation of TLR-dependent MyD88 and TRIF signaling pathways by free zinc ions

From defense to offense: Modulating toll-like receptors to combat arbovirus infections

Arboviruses are a significant threat to global public health, with outbreaks occurring worldwide. Toll-like receptors (TLRs) play a crucial role in the innate immune response against these viruses by recognizing pathogen-associated molecular patterns and initiating an inflammatory response. Significantly, TLRs commonly implicated in the immune response against viral infections include TLR2, TLR4, TLR6, TLR3, TLR7, and TLR8; limiting or allowing them to replicate and spread within the host. Modulating TLRs has emerged as a promising approach to combat arbovirus infections. This review summarizes recent advances in TLR modulation as a therapeutic target in arbovirus infections. Studies have shown that the activation of TLRs can enhance the immune response against arbovirus infections, leading to increased viral clearance and protection against disease. Conversely, inhibition of TLRs can reduce the excessive inflammation and tissue damage associated with arbovirus infection. Modulating TLRs represents a potential therapeutic strategy to combat arbovirus infections.

Design, Synthesis, and Bioactivity Evaluation of a TF-Based Cancer Vaccine Candidate Using Lipid A Mimetics As a Built-In Adjuvant

This study describes the design and synthesis of five TF-based cancer vaccine candidates using a lipid A mimetic as the carrier and a built-in adjuvant. All synthesized conjugates elicited robust and consistent TF-specific immune responses in mice without external adjuvants. Immunological studies subsequently conducted in wild-type and TLR4 knockout C57BL/6 mice demonstrated that the activation of TLR4 was the main reason that the synthesized lipid A mimetics increased the TF-specific immune responses. All antisera induced by these conjugates can specifically recognize, bind to, and induce the lysis of TF-positive cancer cells. Moreover, representative conjugates 2 and 3 could effectively reduce the growth of tumors and prolong the survival time of mice in vivo, and the efficacies were better than glycoprotein TF-CRM197 with alum adjuvant. Lipid A mimetics could therefore be a promising platform for the development of new carbohydrate-based vaccine carriers with self-adjuvanting properties for the treatment of cancer.

Strategies for the development of metalloimmunotherapies

Metal ions play crucial roles in the regulation of immune pathways. In fact, metallodrugs have a long record of accomplishment as effective treatments for a wide range of diseases. Here we argue that the modulation of interactions of metal ions with molecules and cells involved in the immune system forms the basis of a new class of immunotherapies. By examining how metal ions modulate the innate and adaptive immune systems, as well as host-microbiota interactions, we discuss strategies for the development of such metalloimmunotherapies for the treatment of cancer and other immune-related diseases.

Regulation of anti-tumor immunity by metal ion in the tumor microenvironment

Metal ions play an essential role in regulating the functions of immune cells by transmitting intracellular and extracellular signals in tumor microenvironment (TME). Among these immune cells, we focused on the impact of metal ions on T cells because they can recognize and kill cancer cells and play an important role in immune-based cancer treatment. Metal ions are often used in nanomedicines for tumor immunotherapy. In this review, we discuss seven metal ions related to anti-tumor immunity, elucidate their roles in immunotherapy, and provide novel insights into tumor immunotherapy and clinical applications.

Recent advances in different interactions between toll-like receptors and hepatitis B infection: a review

Hepatitis B virus (HBV) B infections remain a primary global health concern. The immunopathology of the infection, specifically the interactions between HBV and the host immune system, remains somewhat unknown. It has been discovered that innate immune reactions are vital in eliminating HBV. Toll-like receptors (TLRs) are an essential category of proteins that detect pathogen-associated molecular patterns (PAMPs). They begin pathways of intracellular signals to stimulate pro-inflammatory and anti-inflammatory cytokines, thus forming adaptive immune reactions. HBV TLRs include TLR2, TLR3, TLR4, TLR7 and TLR9. Each TLR has its particular molecule to recognize; various TLRs impact HBV and play distinct roles in the pathogenesis of the disease. TLR gene polymorphisms may have an advantageous or disadvantageous efficacy on HBV infection, and some single nucleotide polymorphisms (SNPs) can influence the progression or prognosis of infection. Additionally, it has been discovered that similar SNPs in TLR genes might have varied effects on distinct populations due to stress, diet, and external physical variables. In addition, activation of TLR-interceded signaling pathways could suppress HBV replication and increase HBV-particular T-cell and B-cell reactions. By identifying these associated polymorphisms, we can efficiently advance the immune efficacy of vaccines. Additionally, this will enhance our capability to forecast the danger of HBV infection or the threat of dependent liver disease development via several TLR SNPs, thus playing a role in the inhibition, monitoring, and even treatment guidance for HBV infection. This review will show TLR polymorphisms, their influence on TLR signaling, and their associations with HBV diseases.

Zinc deficiency enhances sensitivity to influenza A associated bacterial pneumonia in mice

Although zinc deficiency (secondary to malnutrition) has long been considered an important contributor to morbidity and mortality of infectious disease (e.g. diarrhea disorders), epidemiologic data (including randomized controlled trials with supplemental zinc) for such a role in lower respiratory tract infection are somewhat ambiguous. In the current study, we provide the first preclinical evidence demonstrating that although diet-induced acute zinc deficiency (Zn-D: ~50% decrease) did not worsen infection induced by either influenza A (H1N1) or methicillin-resistant staph aureus (MRSA), Zn-D mice were sensitive to the injurious effects of superinfection of H1N1 with MRSA. Although the mechanism underlying the sensitivity of ZnD mice to combined H1N1/MRSA infection is unclear, it was noteworthy that this combination exacerbated lung injury as shown by lung epithelial injury markers (increased BAL protein) and decreased genes related to epithelial integrity in Zn-D mice (surfactant protein C and secretoglobins family 1A member 1). As bacterial pneumonia accounts for 25%-50% of morbidity and mortality from influenza A infection, zinc deficiency may be an important pathology component of respiratory tract infections.

The changes and potential effects of zinc homeostasis in periodontitis microenvironment

Zinc is a very important and ubiquitous element, which is present in oral environment, daily diet, oral health products, dental restorative materials, and so on. However, there is a lack of attention to the role of both extracellular or intracellular zinc in the progression of periodontitis and periodontal regeneration. This review summarizes the characteristics of immunological microenvironment and host cells function in several key stages of periodontitis progression, and explores the regulatory effect of zinc during this process. We find multiple evidence indicate that zinc may be involved and play a key role in the stages of immune defense, inflammatory response and bone remodeling. Zinc supplementation in an appropriate dose range or regulation of zinc transport proteins can promote periodontal regeneration by either enhancing immune defense or up-regulating local cells proliferation and differentiation functions. Therefore, zinc homeostasis is essential in periodontal remodeling and regeneration. More attention is suggested to be focused on zinc homeostasis regulation and consider it as a potential strategy in the studies on periodontitis treatment, periodontal-guided tissue regeneration, implant material transformation, and so on.

Antiviral activity of zinc against hepatitis viruses: current status and future prospects

Viral hepatitis is a major public health concern globally. World health organization aims at eliminating viral hepatitis as a public health threat by 2030. Among the hepatitis causing viruses, hepatitis B and C are primarily transmitted via contaminated blood. Hepatitis A and E, which gets transmitted primarily via the feco-oral route, are the leading cause of acute viral hepatitis. Although vaccines are available against some of these viruses, new cases continue to be reported. There is an urgent need to devise a potent yet economical antiviral strategy against the hepatitis-causing viruses (denoted as hepatitis viruses) for achieving global elimination of viral hepatitis. Although zinc was known to mankind for a long time (since before Christ era), it was identified as an element in 1746 and its importance for human health was discovered in 1963 by the pioneering work of Dr. Ananda S. Prasad. A series of follow up studies involving zinc supplementation as a therapy demonstrated zinc as an essential element for humans, leading to establishment of a recommended dietary allowance (RDA) of 15 milligram zinc [United States RDA for zinc]. Being an essential component of many cellular enzymes and transcription factors, zinc is vital for growth and homeostasis of most living organisms, including human. Importantly, several studies indicate potent antiviral activity of zinc. Multiple studies have demonstrated antiviral activity of zinc against viruses that cause hepatitis. This article provides a comprehensive overview of the findings on antiviral activity of zinc against hepatitis viruses, discusses the mechanisms underlying the antiviral properties of zinc and summarizes the prospects of harnessing the therapeutic benefit of zinc supplementation therapy in reducing the disease burden due to viral hepatitis.

Angiogenic and immunomodulation role of ions for initial stages of bone tissue regeneration

It is widely known that bone has intrinsic capacity to self-regenerate after injury. However, the physiological regeneration process can be impaired when there is an extensive damage. One of the main reasons is due to the inability to establish a new vascular network that ensures oxygen and nutrient diffusion, leading to a necrotic core and non-junction of bone. Initially, bone tissue engineering (BTE) emerged to use inert biomaterials to just fill bone defects, but it eventually evolved to mimic bone extracellular matrix and even stimulate bone physiological regeneration process. In this regard, the stimulation of osteogenesis has gained a lot of attention especially in the proper stimulation of angiogenesis, being critical to achieve a successful osteogenesis for bone regeneration. Besides, the immunomodulation of a pro-inflammatory environment towards an anti-inflammatory one upon scaffold implantation has been considered another key process for a proper tissue restoration. To stimulate these phases, growth factors and cytokines have been extensively used. Nonetheless, they present some drawbacks such as low stability and safety concerns. Alternatively, the use of inorganic ions has attracted higher attention due to their higher stability and therapeutic effects with low side effects. This review will first focus in giving fundamental aspects of initial bone regeneration phases, focusing mainly on inflammatory and angiogenic ones. Then, it will describe the role of different inorganic ions in modulating the immune response upon biomaterial implantation towards a restorative environment and their ability to stimulate angiogenic response for a proper scaffold vascularization and successful bone tissue restoration. STATEMENT OF SIGNIFICANCE: The impairment of bone tissue regeneration when there is excessive damage has led to different tissue engineered strategies to promote bone healing. Significant importance has been given in the immunomodulation towards an anti-inflammatory environment together with proper angiogenesis stimulation in order to achieve successful bone regeneration rather than stimulating only the osteogenic differentiation. Ions have been considered potential candidates to stimulate these events due to their high stability and therapeutic effects with low side effects compared to growth factors. However, up to now, no review has been published assembling all this information together, describing individual effects of ions on immunomodulation and angiogenic stimulation, as well as their multifunctionality or synergistic effects when combined together.

Effects of combined cannabidiol (CBD) and hops (Humulus lupulus) terpene extract treatment on RAW 264.7 macrophage viability and inflammatory markers

This study investigates the potential of cannabidiol (CBD), one major cannabinoid of the plant Cannabis sativa, alone and in combination with a terpene-enriched extract from Humulus lupulus ("Hops 1"), on the LPS-response of RAW 264.7 macrophages as an established in vitro model of inflammation. With the present study, we could support earlier findings of the anti-inflammatory potential of CBD, which showed a dose-dependent [0-5 µM] reduction in nitric oxide and tumor necrosis factor-alpha (TNF-α) released by LPS-stimulated RAW 264.7 macrophages. Moreover, we observed an additive anti-inflammatory effect after combined CBD [5 µM] and hops extract [40 µg/mL] treatment. The combination of CBD and Hops 1 showed effects in LPS-stimulated RAW 264.7 cells superior to the single substance treatments and akin to the control hydrocortisone. Furthermore, cellular CBD uptake increased dose-dependently in the presence of terpenes from Hops 1 extract. The anti-inflammatory effect of CBD and its cellular uptake positively correlated with terpene concentration, as indicated by comparison with a hemp extract containing both CBD and terpenes. These findings may contribute to the postulations for the so-called "entourage effect" between cannabinoids and terpenes and support the potential of CBD combined with phytomolecules from a non-cannabinoid source, such as hops, for the treatment of inflammatory diseases.

Obesity and dysregulated innate immune responses: impact of micronutrient deficiencies

Obesity is associated with the development of various complications, including diabetes, atherosclerosis, and an increased risk for infections, driven by dysfunctional innate immune responses. Recent insights have revealed that the availability of nutrients is a key determinant of innate immune cell function. Although the presence of obesity is associated with overnutrition of macronutrients, several micronutrient deficiencies, including Vitamin D and zinc, are often present. Micronutrients have been attributed important immunomodulatory roles. In this review, we summarize current knowledge of the immunomodulatory effects of Vitamin D and zinc. We also suggest future lines of research to further improve our understanding of these micronutrients; this may serve as a stepping-stone to explore micronutrient supplementation to improve innate immune cell function during obesity.

A Zinc- and Calcium-Rich Lysosomal Nanoreactor Rescues Monocyte/Macrophage Dysfunction under Sepsis

Sepsis is a dysregulation of the immune response to pathogens and has high morbidity and mortality worldwide. However, the unclear mapping and course of dysregulated immune cells currently hinders the development of advanced therapeutic strategies to treat sepsis. Here, evidence is provided using single-cell RNA sequencing from peripheral blood mononuclear cells in sepsis that pathogens attacking monocytes/macrophages disrupt their immune function. The results reveal an enormous decline in monocytes/macrophages in sepsis and chart the evolution of their impaired phagocytosis (Pha) capabilities. Inspired by these findings, nanoparticles, named "Alpha-MOFs," are developed that target dysfunctional monocytes/macrophages to actively (A) lift (L) Pha by the release of lysosome-sensitive ions from a mineralized metal-organic framework (MOF). Alpha-MOFs have good stability and biosafety in peripheral blood and efficiently targeted monocytes/macrophages. They also release calcium and zinc ions into monocyte/macrophage lysosomes to promote the Pha and degradation of bacteria. Taken together, these results suggest that Alpha-MOFs rescue monocytes/macrophages dysfunction and effectively improve their survival rate during sepsis.

Design, synthesis and immunological evaluation of monophosphoryl lipid A derivatives as adjuvants for a RBD-hFc based SARS-CoV-2 vaccine

Toll-like receptor 4 (TLR4) is a reliable target for the development of vaccine adjuvants. To identify novel TLR4 ligands with improved immunological properties for use as adjuvants for a RBD-hFc based SARS-CoV-2 vaccine, herein, natural E. coli monophosphoryl lipid A (MPLA) and nine of its derivatives were designed and synthesized. Immunological evaluation showed that compounds 1, 3, 5 and 7 exhibited comparative or better adjuvant activity than clinically used Al adjuvants, and are expected to be a promising platform for the development of new adjuvants used for a RBD-hFc based SARS-CoV-2 vaccine. Preliminary structure-activity relationship analysis of the MPLA derivatives showed that the replacement of the functional groups at the C-1, C-4' or C-6' position of E. coli MPLA has an effect on its biological activity. In addition, we found that the combination of MPLA and Al was feasible for immunotherapy and could further enhance immune responses, providing a new direction toward the immunological enhancement of RBD-hFc based SARS-CoV-2 vaccines.

Nano-antivirals: A comprehensive review

Nanoparticles can be used as inhibitory agents against various microorganisms, including bacteria, algae, archaea, fungi, and a huge class of viruses. The mechanism of action includes inhibiting the function of the cell membrane/stopping the synthesis of the cell membrane, disturbing the transduction of energy, producing toxic reactive oxygen species (ROS), and inhibiting or reducing RNA and DNA production. Various nanomaterials, including different metallic, silicon, and carbon-based nanomaterials and nanoarchitectures, have been successfully used against different viruses. Recent research strongly agrees that these nanoarchitecture-based virucidal materials (nano-antivirals) have shown activity in the solid state. Therefore, they are very useful in the development of several products, such as fabric and high-touch surfaces. This review thoroughly and critically identifies recently developed nano-antivirals and their products, nano-antiviral deposition methods on various substrates, and possible mechanisms of action. By considering the commercial viability of nano-antivirals, recommendations are made to develop scalable and sustainable nano-antiviral products with contact-killing properties.

The relationship between nutrition and the immune system

Nutrition plays an essential role in the regulation of optimal immunological response, by providing adequate nutrients in sufficient concentrations to immune cells. There are a large number of micronutrients, such as minerals, and vitamins, as well as some macronutrients such as some amino acids, cholesterol and fatty acids demonstrated to exert a very important and specific impact on appropriate immune activity. This review aims to summarize at some extent the large amount of data accrued to date related to the modulation of immune function by certain micro and macronutrients and to emphasize their importance in maintaining human health. Thus, among many, some relevant case in point examples are brought and discussed: (1) The role of vitamin A/all-trans-retinoic-acids (ATRA) in acute promyelocytic leukemia, being this vitamin utilized as a very efficient therapeutic agent via effective modulation of the immune function (2) The involvement of vitamin C in the fight against tumor cells via the increase of the number of active NK cells. (3) The stimulation of apoptosis, the suppression of cancer cell proliferation, and delayed tumor development mediated by calcitriol/vitamin D by means of immunity regulation (4) The use of selenium as a cofactor to reach more effective immune response to COVID vaccination (5). The crucial role of cholesterol to regulate the immune function, which is demonstrated to be very sensitive to the variations of this macronutrient concentration. Other important examples are reviewed as well.

Zinc in Human Health and Infectious Diseases

During the last few decades, the micronutrient zinc has proven to be an important metal ion for a well-functioning immune system, and thus also for a suitable immune defense. Nowadays, it is known that the main cause of zinc deficiency is malnutrition. In particular, vulnerable populations, such as the elderly in Western countries and children in developing countries, are often affected. However, sufficient zinc intake and homeostasis is essential for a healthy life, as it is known that zinc deficiency is associated with a multitude of immune disorders such as metabolic and chronic diseases, as well as infectious diseases such as respiratory infections, malaria, HIV, or tuberculosis. Moreover, the modulation of the proinflammatory immune response and oxidative stress is well described. The anti-inflammatory and antioxidant properties of zinc have been known for a long time, but are not comprehensively researched and understood yet. Therefore, this review highlights the current molecular mechanisms underlying the development of a pro-/ and anti-inflammatory immune response as a result of zinc deficiency and zinc supplementation. Additionally, we emphasize the potential of zinc as a preventive and therapeutic agent, alone or in combination with other strategies, that could ameliorate infectious diseases.

Current Research on Zinc Oxide Nanoparticles: Synthesis, Characterization, and Biomedical Applications

Zinc oxide nanoparticles (ZnO-NPs) have piqued the curiosity of researchers all over the world due to their extensive biological activity. They are less toxic and biodegradable with the capacity to greatly boost pharmacophore bioactivity. ZnO-NPs are the most extensively used metal oxide nanoparticles in electronic and optoelectronics because of their distinctive optical and chemical properties which can be readily modified by altering the morphology and the wide bandgap. The biosynthesis of nanoparticles using extracts of therapeutic plants, fungi, bacteria, algae, etc., improves their stability and biocompatibility in many biological settings, and its biofabrication alters its physiochemical behavior, contributing to biological potency. As such, ZnO-NPs can be used as an effective nanocarrier for conventional drugs due to their cost-effectiveness and benefits of being biodegradable and biocompatible. This article covers a comprehensive review of different synthesis approaches of ZnO-NPs including physical, chemical, biochemical, and green synthesis techniques, and also emphasizes their biopotency through antibacterial, antifungal, anticancer, anti-inflammatory, antidiabetic, antioxidant, antiviral, wound healing, and cardioprotective activity. Green synthesis from plants, bacteria, and fungus is given special attention, with a particular emphasis on extraction techniques, precursors used for the synthesis and reaction conditions, characterization techniques, and surface morphology of the particles.

The soluble CD83 protein prevents bone destruction by inhibiting the formation of osteoclasts and inducing resolution of inflammation in arthritis

Here we show that soluble CD83 induces the resolution of inflammation in an antigen-induced arthritis (AIA) model. Joint swelling and the arthritis-related expression levels of IL-1β, IL-6, RANKL, MMP9, and OC-Stamp were strongly reduced, while Foxp3 was induced. In addition, we observed a significant inhibition of TRAP⁺ osteoclast formation, correlating with the reduced arthritic disease score. In contrast, cell-specific deletion of CD83 in human and murine precursor cells resulted in an enhanced formation of mature osteoclasts. RNA sequencing analyses, comparing sCD83- with mock treated cells, revealed a strong downregulation of osteoclastogenic factors, such as Oc-Stamp, Mmp9 and Nfatc1, Ctsk, and Trap. Concomitantly, transcripts typical for pro-resolving macrophages, e.g., Mrc1/2, Marco, Klf4, and Mertk, were upregulated. Interestingly, members of the metallothionein (MT) family, which have been associated with a reduced arthritic disease severity, were also highly induced by sCD83 in samples derived from RA patients. Finally, we elucidated the sCD83-induced signaling cascade downstream to its binding to the Toll-like receptor 4/(TLR4/MD2) receptor complex using CRISPR/Cas9-induced knockdowns of TLR4/MyD88/TRIF and MTs, revealing that sCD83 acts via the TRIF-signaling cascade. In conclusion, sCD83 represents a promising therapeutic approach to induce the resolution of inflammation and to prevent bone erosion in autoimmune arthritis.

AIF-1 and RNASET2 are involved in the inflammatory response in the Mediterranean mussel Mytilus galloprovincialis following Vibrio infection

Filter-feeding bivalves, such as the Mytilus species, are exposed to different types of bacteria in the surrounding waters, in particular of the Vibrio genus. Mussels lack an adaptive immune system and hemocytes can recognize pathogen-associated molecular patterns (PAMPs) via pattern recognition receptors (PRRs) to activate intracellular signaling pathways to trigger the antimicrobial effectors synthesis. Among the areas of bivalve immunity that deserve study include the role of hemocyte subpopulations. Since little information are available on immune responses at the tissue level to human pathogenic vibrios commonly detected in coastal waters involved in seafood-borne diseases, in this work, immunological parameters of the hemocytes from the Mediterranean mussel M. galloprovincialis were evaluated in response to in vivo challenge with Vibrio splendidus. The histological approach has been first used in order to identify the hemocytes recruitment at the infection site and the morphological change of muscular fibers. In addition, using immunolabeling with specific antibody we detected the production of molecules involved in the inflammatory activated cascade: Toll-like receptors 4 (TLR4), the myeloid differentiation factor 88 (MyD88), the Allograft inflammatory factor-1 (AIF-1) and the ribonucleases RNASET2, belonging to the T2 family, that in vertebrates are involved in the recruitment and activation of macrophages. Our results indicate the activation of TLR4 during bacterial infection preparatory to the recruitment of the MyD88 adapter with a putative role in recognition and intracellular signalling. Furthermore, the data presented in this work suggest that challenging with Gram-negative bacteria causes a massive migration of AIF-1⁺ hemocytes and that the ribonuclease RNASET2 could play a key role in the recruitment of these activated hemocytes. Our approach is useful for further understanding the complex molecular defence mechanisms of the host in invertebrates, especially in relation to the need to develop methods to evaluate the immunological response of bivalve molluscs used in aquaculture.

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.

Chemical regulation of the cGAS-STING pathway

Nucleic acids represent a major class of pathogen and damage signatures, recognized by a variety of host sensors to initiate signaling cascades and immune responses, such as mechanisms of RLR-MAVS, cGAS-STING, TLR-TRIF, and AIM2 inflammasome. Yet, an outstanding challenge is understanding how nucleic acid sensing initiates immune responses and its tethering in various infectious, cancerous, autoimmune, and inflammatory diseases. However, the discovery and application of a plethora of small molecule compounds have substantially facilitated this process. This review provides an overview and recent development of the innate DNA-sensing pathway of cGAS-STING and highlights the multiple agonists and inhibitors in fine-tuning the pathway that can be exploited to improve disease treatment, focusing primarily on crucial pathway components and regulators.

Antiviral Activity of Zinc Oxide Nanoparticles and Tetrapods Against the Hepatitis E and Hepatitis C Viruses

Hepatitis E virus (HEV) causes an acute, self-limiting hepatitis. The disease takes a severe form in pregnant women, leading to around 30% mortality. Zinc is an essential micronutrient that plays a crucial role in multiple cellular processes. Our earlier findings demonstrated the antiviral activity of zinc salts against HEV infection. Zinc oxide (ZnO) and its nanostructures have attracted marked interest due to their unique characteristics. Here we synthesized ZnO nanoparticles [ZnO(NP)] and tetrapod-shaped ZnO nanoparticles [ZnO(TP)] and evaluated their antiviral activity. Both ZnO(NP) and ZnO(TP) displayed potent antiviral activity against hepatitis E and hepatitis C viruses, with the latter being more effective. Measurement of cell viability and intracellular reactive oxygen species levels revealed that both ZnO(NP) and ZnO(TP) are noncytotoxic to the cells even at significantly higher doses, compared to a conventional zinc salt (ZnSO₄). Our study paves the way for evaluation of the potential therapeutic benefit of ZnO(TP) against HEV and HCV.

Toll-like receptors change morphine-induced antinociception, tolerance and dependence: Studies using male and female TLR and signalling gene KO mice

Toll-like receptors (TLR) have been proposed as a site of action that alters opioid pharmacodynamics. However, a comprehensive assessment of acute opioid antinociception, tolerance and withdrawal behaviours in genetic null mutant strains with altered innate immune signalling has not been performed. Nor has the impact of genetic deletion of TLR2/4 on high-affinity opioid receptor binding. Here we show that diminished TLR signalling potentiates acute morphine antinociception equally in male and female mice. However, only male TIR8 null mutant mice showed reduced morphine analgesia. Analgesic tolerance was prevented in TLR2 and TLR4 null mutants, but not MyD88 animals. Withdrawal behaviours were only protected in TLR2^-/- mice. In silico docking simulations revealed opioid ligands bound preferentially to the LPS binding pocket of MD-2 rather than TLR4. There was no binding of [³H](-)-naloxone or [³H]diprenorphine to TLR4 in the concentrations explored. These data confirm that opioids have high efficacy activity at innate immune pattern recognition binding sites but do not bind to TLR4 and identify critical pathway and sex-specific effects of the complex innate immune signalling contributions to opioid pharmacodynamics. These data further support the behavioural importance of the TLR-opioid interaction but fail to demonstrate direct evidence for high-affinity binding of the TLR4 signalling complex to ligands.

Titanium Surface Characteristics Induce the Specific Reprogramming of Toll-like Receptor Signaling in Macrophages

Most of the research on titanium-based dental implants (Ti-discs) is focused on how they are able to stimulate the formation of new tissue and/or cytotoxic studies, with very scarce data on their effects on functional responses by immunocompetent cells. In particular, the link between the rewiring of innate immune responses and surface biomaterials properties is poorly understood. To address this, we characterize the functional response of macrophage cultures to four different dental titanium surfaces (MA: mechanical abrasion; SB + AE: sandblasting plus etching; SB: sandblasting; AE: acid etching). We use different Toll-like receptor (TLR) ligands towards cell surface receptors (bacterial lipopolysaccharide LPS for TLR4; imiquimod for TLR7; synthetic bacterial triacylated lipoprotein for TLR2/TLR1) and endosomal membrane receptor (poly I:C for TLR3) to simulate bacterial (cell wall bacterial components) or viral infections (dsRNA and ssRNA). The extracellular and total LDH levels indicate that exposure to the different Ti-surfaces is not cytotoxic for macrophages under resting or TLR-stimulated conditions, although there is a tendency towards an impairment in macrophage proliferation, viability or adhesion under TLR4, TLR3 and TLR2/1 stimulations in SB discs cultures. The secreted IL-6 and IL-10 levels are not modified upon resting macrophage exposure to the Ti-surfaces studied as well as steady state levels of iNos or ArgI mRNA. However, macrophage exposure to MA Ti-surface do display an enhanced immune response to TLR4, TLR7 or TLR2/1 compared to other Ti-surfaces in terms of soluble immune mediators secreted and M1/M2 gene expression profiling. This change of characteristics in cellular phenotype might be related to changes in cellular morphology. Remarkably, the gene expression of Tlr3 is the only TLR that is differentially affected by distinct Ti-surface exposure. These results highlight the relevance of patterned substrates in dental implants to achieve a smart manipulation of the immune responses in the context of personalized medicine, cell-based therapies, preferential lineage commitment of precursor cells or control of tissue architecture in oral biology.

TLR Signals in Epithelial Cells in the Nasal Cavity and Paranasal Sinuses

The respiratory tract is constantly at risk of invasion by microorganisms such as bacteria, viruses, and fungi. In particular, the mucosal epithelium of the nasal cavity and paranasal sinuses is at the very forefront of the battles between the host and the invading pathogens. Recent studies have revealed that the epithelium not only constitutes a physical barrier but also takes an essential role in the activation of the immune system. One of the mechanisms equipped in the epithelium to fight against microorganisms is the Toll-like receptor (TLR) response. TLRs recognize common structural components of microorganisms and activate the innate immune system, resulting in the production of a plethora of cytokines and chemokines in the response against microbes. As the epithelia-derived cytokines are deeply involved in the pathogenesis of inflammatory conditions in the nasal cavity and paranasal sinuses, such as chronic rhinosinusitis (CRS) and allergic rhinitis (AR), the molecules involved in the TLR response may be utilized as therapeutic targets for these diseases. There are several differences in the TLR response between nasal and bronchial epithelial cells, and knowledge of the TLR signals in the upper airway is sparse compared to that in the lower airway. In this review, we provide recent evidence on TLR signaling in the upper airway, focusing on the expression, regulation, and responsiveness of TLRs in human nasal epithelial cells (HNECs). We also discuss how TLRs in the epithelium are involved in the pathogenesis of, and possible therapeutic targeting, for CRS and AR.

Rebalancing the unbalanced aged immune system - A special focus on zinc

Nowadays, aging is understood as a dynamic and multifaceted dysregulation process that spares almost no human organ or cell. The immune system being among the most affected, it has been shown predominantly that its integrity determines the tightrope walk between the difference of escaping or suffering from age-related diseases. Next to drug-based anti-aging strategies, micronutrient intervention may represent an emerging but less radical way to slow immune aging. While a sufficient supply of a variety of micronutrients is undeniably important, adequate intake of the trace element zinc appears to tower over others in terms of reaching old age. Inconveniently, zinc deficiency prevalence among the elderly is high, which in turn contributes to increased susceptibility to infection, decreased anti-tumor immunity as well as attenuated response to vaccination. Driven by this research, this review aims to provide a comprehensive and up-to-date overview of the various rebalancing capabilities of zinc in the unbalanced immune system of the elderly. This includes an in-depth and cell type-centered discussion on the role of zinc in immunosenescence and inflammaging. We further address upcoming translational aspects e.g. how zinc deficiency promotes the flourishing of certain pathogenic taxa of the gut microbiome and how zinc supply counteracts such alterations in a manner that may contribute to longevity. In the light of the ongoing COVID-19 pandemic, we also briefly review current knowledge on the interdependency between age, zinc status, and respiratory infections. Based on two concrete examples and considering the latest findings in the field we conclude our remarks by outlining tremendous parallels between suboptimal zinc status and accelerated aging on the one hand and an optimized zinc status and successful aging on the other hand.

Cytoplasmic zinc promotes IL-1β production by monocytes and macrophages through mTORC1-induced glycolysis in rheumatoid arthritis

[Figure: see text].

Metallothionein 3-Zinc Axis Suppresses Caspase-11 Inflammasome Activation and Impairs Antibacterial Immunity

Non-canonical inflammasome activation by mouse caspase-11 (or human CASPASE-4/5) is crucial for the clearance of certain gram-negative bacterial infections, but can lead to severe inflammatory damage. Factors that promote non-canonical inflammasome activation are well recognized, but less is known about the mechanisms underlying its negative regulation. Herein, we identify that the caspase-11 inflammasome in mouse and human macrophages (Mϕ) is negatively controlled by the zinc (Zn2+) regulating protein, metallothionein 3 (MT3). Upon challenge with intracellular lipopolysaccharide (iLPS), Mϕ increased MT3 expression that curtailed the activation of caspase-11 and its downstream targets caspase-1 and interleukin (IL)-1β. Mechanistically, MT3 increased intramacrophage Zn2+ to downmodulate the TRIF-IRF3-STAT1 axis that is prerequisite for caspase-11 effector function. In vivo, MT3 suppressed activation of the caspase-11 inflammasome, while caspase-11 and MT3 synergized in impairing antibacterial immunity. The present study identifies an important yin-yang relationship between the non-canonical inflammasome and MT3 in controlling inflammation and immunity to gram-negative bacteria.

Evaluation of the anti-inflammatory effects of surface-reaction-type pre-reacted glass-ionomer filler containing root canal sealer in lipopolysaccharide-stimulated RAW264.7 macrophages

A prototype surface-reaction-type pre-reacted glass-ionomer (S-PRG) filler containing root canal sealer (S-PRG sealer) exhibits bioactive potential by releasing multiple ions. This study explored the suppressive effects and modes of action of S-PRG sealer extracts on proinflammatory cytokine expression in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Expression of proinflammatory cytokines was evaluated by RT-qPCR and ELISA. Expression of phosphorylated nuclear factor-kappa B (p-NF-kB) p65 was evaluated by western blotting. S-PRG sealer extracts significantly downregulated mRNA expression levels of interleukin (IL)-1α, IL-6, and TNF-α in LPS-stimulated RAW264.7 cells; the extracts also reduced the levels of IL-6 protein and p-NF-kB. In order to verify that Zn²⁺ was responsible for downregulation of proinflammatory cytokine expression, N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN) was used as a heavy metal chelator with strong affinity for Zn²⁺. These effects were mitigated by TPEN. The application of ZnCl₂ reproduced the actions of S-PRG sealer extracts. These data suggest that S-PRG sealer has anti-inflammatory potential involving heavy metal ions such as Zn²⁺.

The correlation between serum selenium, zinc, and COVID-19 severity: an observational study

Background

Without an adequate immune response, SARS-CoV2 virus can simply spread throughout the body of the host. Two of the well-known immunonutrients are selenium (Se) and zinc (Zn). Se and Zn deficiency might lead to inflammation, oxidative stress, and viral entry into the cells by decreasing ACE-2 expression; three factors that are proposed to be involved in COVID-19 pathogenesis. Thus, in the current study we aimed at evaluating the correlation between serum Se and Zn status and COVID-19 severity.

Methods

Eighty-four COVID-19 patients were enrolled in this observational study. Patients were diagnosed based on an infectious disease specialist diagnosis, using WHO interim guidance and the recommendations of the Iranian National Committee of Covid-19. The patients with acute respiratory tract infection symptoms were checked for compatibility of chest computed tomography (CT) scan results with that of Covid-19 and Real-time polymerase chain reaction (RT-PCR) for corona virus infection. The severity of Covid-19 was categorized into three groups (mild, moderate, and severe) using CDC criteria. Serum Zn and Se level of all subjects was measured. The severity of the disease was determined only once at the onset of disease.

Results

According to the results of linear regression test, there was a significant association between Zn and Se level and COVID-19 severity (β = − 0.28, P-value = 0.01 for Se; β = − 0.26, P-value = 0.02). However the significance disappeared after adjusting for confounding factors. Spearman correlation analysis showed a significant negative association between serum Zn, Se and CRP level (r = − 0.35, P-value = 0.001 for Se; r = − 0.41, P-value < 0.001 for Zn).

Conclusion

Results suggest that increasing levels of Se and Zn were accompanied by a decrease in serum CRP level. However, the significant association between Se, Zn, and disease severity was lost after adjusting for confounding factors.

Modulation of Toll-like receptor 1 intracellular domain structure and activity by Zn2+ ions

Toll-like receptors (TLRs) play an important role in the innate immune response. While a lot is known about the structures of their extracellular parts, many questions are still left unanswered, when the structural basis of TLR activation is analyzed for the TLR intracellular domains. Here we report the structure and dynamics of TLR1 toll-interleukin like (TIR) cytoplasmic domain in crystal and in solution. We found that the TLR1-TIR domain is capable of specific binding of Zn with nanomolar affinity. Interactions with Zn are mediated by cysteine residues 667 and 686 and C667 is essential for the Zn binding. Potential structures of the TLR1-TIR/Zn complex were predicted in silico. Using the functional assays for the heterodimeric TLR1/2 receptor, we found that both Zn addition and Zn depletion affect the activity of TLR1, and C667A mutation disrupts the receptor activity. Analysis of C667 position in the TLR1 structure and possible effects of C667A mutation, suggests that zinc-binding ability of TLR1-TIR domain is critical for the receptor activation.

Lushpa et al report the structure and dynamics of the TLR1 toll-interleukin like (TIR) cytoplasmic domain in both crystal and solution. They demonstrate that the TLR1 TIR domain is capable of specific binding of Zn with nanomolar affinity, which appears to be critical for receptor activation, and provide potential structures TLR1-TIR/Zn complex based on in silico data.

Dietary and Physiological Effects of Zinc on the Immune System

Evidence for the importance of zinc for all immune cells and for mounting an efficient and balanced immune response to various environmental stressors has been accumulating in recent years. This article describes the role of zinc in fundamental biological processes and summarizes our current knowledge of zinc's effect on hematopoiesis, including differentiation into immune cell subtypes. In addition, the important role of zinc during activation and function of immune cells is detailed and associated with the specific immune responses to bacteria, parasites, and viruses. The association of zinc with autoimmune reactions and cancers as diseases with increased or decreased immune responses is also discussed. This article provides a broad overview of the manifold roles that zinc, or its deficiency, plays in physiology and during various diseases. Consequently, we discuss why zinc supplementation should be considered, especially for people at risk of deficiency. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Knockdown of Mitogen-Activated Protein Kinase Kinase 3 Negatively Regulates Hepatitis A Virus Replication

Zinc chloride is known to be effective in combatting hepatitis A virus (HAV) infection, and zinc ions seem to be especially involved in Toll-like receptor (TLR) signaling pathways. In the present study, we examined this involvement in human hepatoma cell lines using a human TLR signaling target RT-PCR array. We also observed that zinc chloride inhibited mitogen-activated protein kinase kinase 3 (MAP2K3) expression, which could downregulate HAV replication in human hepatocytes. It is possible that zinc chloride may inhibit HAV replication in association with its inhibition of MAP2K3. In that regard, this study set out to determine whether MAP2K3 could be considered a modulating factor in the development of the HAV pathogen-associated molecular pattern (PAMP) and its triggering of interferon-β production. Because MAP2K3 seems to play a role in antiviral immunity against HAV infection, it is a promising target for drug development. The inhibition of MAP2K3 may also prevent HAV patients from developing a severe hepatitis A infection.

The Influence of Nutritional Factors on Immunological Outcomes

Through food intake, humans obtain a variety of nutrients that are essential for growth, cellular function, tissue development, energy, and immune defense. A special interaction between nutrients and gut-associated lymphoid tissue occurs in the intestinal tract. Enterocytes of the intestinal barrier act as sensors for antigens from nutrients and the intestinal microbiota, which they deliver to the underlying immune system of the lamina propria, triggering an immune response. Studies investigating the mechanism of influence of nutrition on immunological outcomes have highlighted an important role of macronutrients (proteins, carbohydrates, fatty acids) and micronutrients (vitamins, minerals, phytochemicals, antioxidants, probiotics) in modulating immune homeostasis. Nutrients exert their role in innate immunity and inflammation by regulating the expression of TLRs, pro- and anti-inflammatory cytokines, thus interfering with immune cell crosstalk and signaling. Chemical substrates derived from nutrient metabolism may act as cofactors or blockers of enzymatic activity, influencing molecular pathways and chemical reactions associated with microbial killing, inflammation, and oxidative stress. Immune cell function appears to be influenced by certain nutrients that form parts of the cell membrane structure and are involved in energy production and prevention of cytotoxicity. Nutrients also contribute to the initiation and regulation of adaptive immune responses by modulating B and T lymphocyte differentiation, proliferation and activation, and antibody production. The purpose of this review is to present the available data from the field of nutritional immunology to elucidate the complex and dynamic relationship between nutrients and the immune system, the delineation of which will lead to optimized nutritional regimens for disease prevention and patient care.

Regulatory Role of Zinc in Immune Cell Signaling

Zinc is an essential micronutrient with crucial roles in multiple facets of biological processes. Dysregulated zinc homeostasis impairs overall immune function and resultantly increases susceptibility to infection. Clinically, zinc supplementation is practiced for treatment of several infectious diseases, such as diarrhea and malaria. Recent focus on zinc as a beneficial element for immune system support has resulted in investigation of the immunomodulatory roles of zinc in a variety of immune cells. Besides its classical role as a cofactor that regulates the structural function of thousands of proteins, accumulating evidence suggests that zinc also acts, in a manner similar to calcium, as an ionic regulator of immune responses via participation as an intracellular messenger in signaling pathways. In this review, we focus on the role of zinc as a signaling molecule in major pathways such as those downstream of Toll-like receptors-, T cell receptor-, and cytokine-mediated signal transduction that regulate the activity and function of monocytes/macrophages and T cells, principal players in the innate and adaptive immune systems.

Interactions of zinc- and redox-signaling pathways

Zinc and cellular oxidants such as reactive oxygen species (ROS) each participate in a multitude of physiological functions. There is considerable overlap between the affected events, including signal transduction. While there is no obvious direct connection between zinc and ROS, mainly because the bivalent cation zinc does not change its oxidation state in biological systems, these are linked by their interaction with sulfur, forming the remarkable triad of zinc, ROS, and protein thiols. First, zinc binds to reduced thiols and can be released upon oxidation. Thereby, redox signals are translated into changes in the free zinc concentration, which can act as zinc signals. Second, zinc affects oxidation of thiols in several ways, directly as well as indirectly. A protein incorporating many of these interactions is metallothionein (MT), which is rich in cysteine and capable of binding up to seven zinc ions in its fully reduced state. Zinc binding is diminished after (partial) oxidation, while thiols show increased reactivity in the absence of bound metal ions. Adding still more complexity, the MT promoter is controlled by zinc (via metal regulatory transcription factor 1 (MTF-1)) as well as redox (via nuclear factor erythroid 2-related factor 2 (NRF2)). Many signaling cascades that are important for cell proliferation or apoptosis contain protein thiols, acting as centers for crosstalk between zinc- and redox-signaling. A prominent example for shared molecular targets for zinc and ROS are active site cysteine thiols in protein tyrosine phosphatases (PTP), their activity being downregulated by oxidation as well as zinc binding. Because zinc binding also protects PTP thiols form irreversible oxidation, there is a multi-faceted reciprocal interaction, illustrating that zinc- and redox-signaling are intricately linked on multiple levels.

Potential health benefits of zinc supplementation for the management of COVID-19 pandemic

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiological agent for the Coronavirus Disease 2019 (COVID-19). The COVID-19 pandemic has created unimaginable and unprecedented global health crisis. Since the outbreak of COVID-19, millions of dollars have been spent, hospitalization overstretched with increasing morbidity and mortality. All these have resulted in unprecedented global economic catastrophe. Several drugs and vaccines are currently being evaluated, tested, and administered in the frantic efforts to stem the dire consequences of COVID-19 with varying degrees of successes. Zinc possesses potential health benefits against COVID-19 pandemic by improving immune response, minimizing infection and inflammation, preventing lung injury, inhibiting viral replication through the interference of the viral genome transcription, protein translation, attachment, and host infectivity. However, this review focuses on the various mechanisms of action of zinc and its supplementation as adjuvant for vaccines an effective therapeutic regimen in the management of the ravaging COVID-19 pandemic. PRACTICAL APPLICATIONS: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiological agent for the Coronavirus Disease 2019 (COVID-19), has brought unprecedented untold hardship to both developing and developed countries. The global race for vaccine development against COVID-19 continues with success in sight with attendant increasing hospitalization, morbidity, and mortality. Available drugs with anti-inflammatory actions have become alternative to stem the tide of COVID-19 with attendant global financial crises. However, Zinc is known to modulate several physiological functions including intracellular signaling, enzyme function, gustation, and olfaction, as well as reproductive, skeletal, neuronal, and cardiovascular systems. Hence, achieving a significant therapeutic approach against COVID-19 could imply the use of zinc as a supplement together with available drugs and vaccines waiting for emergency authorization to win the battle of COVID-19. Together, it becomes innovative and creative to supplement zinc with currently available drugs and vaccines.

Vitamin D, zinc and glutamine: Synergistic action with OncoTherad immunomodulator in interferon signaling and COVID‑19 (Review)

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified in December, 2019 in Wuhan, China. Since then, it has continued to spread rapidly in numerous countries, while the search for effective therapeutic options persists. Coronaviruses, including SARS-CoV-2, are known to suppress and evade the antiviral responses of the host organism mediated by interferon (IFN), a family of cytokines that plays an important role in antiviral defenses associated with innate immunity, and has been used therapeutically for chronic viral diseases and cancer. On the other hand, OncoTherad, a safe and effective immunotherapeutic agent in the treatment of non-muscle invasive bladder cancer (NMIBC), increases IFN signaling and has been shown to be a promising therapeutic approach for COVID-19 in a case report that described the rapid recovery of a 78-year-old patient with NMIBC with comorbidities. The present review discusses the possible synergistic action of OncoTherad with vitamin D, zinc and glutamine, nutrients that have been shown to facilitate immune responses mediated by IFN signaling, as well as the potential of this combination as a therapeutic option for COVID-19.

Ca-Zn-Ag Alginate Aerogels for Wound Healing Applications: Swelling Behavior in Simulated Human Body Fluids and Effect on Macrophages

Chronic non-healing wounds represent a substantial economic burden to healthcare systems and cause a considerable reduction in quality of life for those affected. Approximately 0.5-2% of the population in developed countries are projected to experience a chronic wound in their lifetime, necessitating further developments in the area of wound care materials. The use of aerogels for wound healing applications has increased due to their high exudate absorbency and ability to incorporate therapeutic substances, amongst them trace metals, to promote wound-healing. This study evaluates the swelling behavior of Ca-Zn-Ag-loaded alginate aerogels and their metal release upon incubation in human sweat or wound fluid substitutes. All aerogels show excellent liquid uptake from any of the formulas and high liquid holding capacities. Calcium is only marginally released into the swelling solvents, thus remaining as alginate bridging component aiding the absorption and fast transfer of liquids into the aerogel network. The zinc transfer quota is similar to those observed for common wound dressings in human and animal injury models. With respect to the immune regulatory function of zinc, cell culture studies show a high availability and anti-inflammatory activity of aerogel released Zn-species in RAW 264.7 macrophages. For silver, the balance between antibacterial effectiveness versus cytotoxicity remains a significant challenge for which the alginate aerogels need to be improved in the future. An increased knowledge of the transformations that alginate aerogels undergo in the course of the fabrication as well as during wound fluid exposure is necessary when aiming to create advanced, tissue-compatible aerogel products.

An alloy of zinc and innate immunity: Galvanising host defence against infection

Innate immune cells such as macrophages and neutrophils initiate protective inflammatory responses and engage antimicrobial responses to provide frontline defence against invading pathogens. These cells can both restrict the availability of certain transition metals that are essential for microbial growth and direct toxic concentrations of metals towards pathogens as antimicrobial responses. Zinc is important for the structure and function of many proteins, however excess zinc can be cytotoxic. In recent years, several studies have revealed that innate immune cells can deliver toxic concentrations of zinc to intracellular pathogens. In this review, we discuss the importance of zinc status during infectious disease and the evidence for zinc intoxication as an innate immune antimicrobial response. Evidence for pathogen subversion of this response is also examined. The likely mechanisms, including the involvement of specific zinc transporters that facilitate delivery of zinc by innate immune cells for metal ion poisoning of pathogens are also considered. Precise mechanisms by which excess levels of zinc can be toxic to microorganisms are then discussed, particularly in the context of synergy with other antimicrobial responses. Finally, we highlight key unanswered questions in this emerging field, which may offer new opportunities for exploiting innate immune responses for anti-infective development.

The Potential Impact of Zinc Supplementation on COVID-19 Pathogenesis

During the current corona pandemic, new therapeutic options against this viral disease are urgently desired. Due to the rapid spread and immense number of affected individuals worldwide, cost-effective, globally available, and safe options with minimal side effects and simple application are extremely warranted. This review will therefore discuss the potential of zinc as preventive and therapeutic agent alone or in combination with other strategies, as zinc meets all the above described criteria. While a variety of data on the association of the individual zinc status with viral and respiratory tract infections are available, study evidence regarding COVID-19 is so far missing but can be assumed as was indicated by others and is detailed in this perspective, focusing on re-balancing of the immune response by zinc supplementation. Especially, the role of zinc in viral-induced vascular complications has barely been discussed, so far. Interestingly, most of the risk groups described for COVID-19 are at the same time groups that were associated with zinc deficiency. As zinc is essential to preserve natural tissue barriers such as the respiratory epithelium, preventing pathogen entry, for a balanced function of the immune system and the redox system, zinc deficiency can probably be added to the factors predisposing individuals to infection and detrimental progression of COVID-19. Finally, due to its direct antiviral properties, it can be assumed that zinc administration is beneficial for most of the population, especially those with suboptimal zinc status.

Type I Interferons Ameliorate Zinc Intoxication of Candida glabrata by Macrophages and Promote Fungal Immune Evasion

Host and fungal pathogens compete for metal ion acquisition during infectious processes, but molecular mechanisms remain largely unknown. Here, we show that type I interferons (IFNs-I) dysregulate zinc homeostasis in macrophages, which employ metallothionein-mediated zinc intoxication of pathogens as fungicidal response. However, Candida glabrata can escape immune surveillance by sequestering zinc into vacuoles. Interestingly, zinc-loading is inhibited by IFNs-I, because a Janus kinase 1 (JAK1)-dependent suppression of zinc homeostasis affects zinc distribution in macrophages as well as generation of reactive oxygen species (ROS). In addition, systemic fungal infections elicit IFN-I responses that suppress splenic zinc homeostasis, thereby altering macrophage zinc pools that otherwise exert fungicidal actions. Thus, IFN-I signaling inadvertently increases fungal fitness both in vitro and in vivo during fungal infections. Our data reveal an as yet unrecognized role for zinc intoxication in antifungal immunity and suggest that interfering with host zinc homeostasis may offer therapeutic options to treat invasive fungal infections.

PCBP2 post-transcriptionally regulates sortilin expression by binding to a C-rich element in its 3' UTR

Post‐transcriptional regulation of cytokine production is crucial to ensure appropriate immune responses. We previously demonstrated that poly‐rC‐binding protein‐1 (PCBP1) can act as a trans‐acting factor to stabilize transcripts encoding sortilin, which mediates cytokine trafficking. Here, we report that PCBP2, which strongly resembles PCBP1, can stabilize sortilin transcripts in macrophages using the same mechanism employed by PCBP1. PCBP2 recognized the C‐rich element in the 3′ UTR of sortilin mRNA, and PCBP2 knockdown decreased sortilin transcripts, indicating that PCBP2 stabilizes sortilin mRNA by binding to its 3′ UTR. Zn²⁺ reversibly inhibited the nucleotide binding ability of PCBP2 in vitro. These findings suggest that both PCBP2 and PCBP1 may control the stability of sortilin transcripts by sensing intracellular Zn²⁺ levels in immune cells.

Potential Role of Trace Elements (Al, Cu, Zn, and Se) in Multiple Sclerosis Physiopathology

Multiple sclerosis (MS) is an unpredictable disease of the central nervous system. The cause of MS is not known completely, and pathology is specified by involved demyelinated areas in the white and gray matter of the brain and spinal cord. Inflammation and peripheral tolerance breakdown due to Treg cell defects and/or effector cell resistance are present at all stages of the disease. Several invading peripheral immune cells are included in the process of the disease such as macrophages, CD8+ T cells, CD4+ T cells, B cells, and plasma cells. Trace elements are known as elements found in soil, plants, and living organisms in small quantities. Some of them (e.g., Al, Cu, Zn, Mn, and Se) are essential for the body's functions like catalysts in enzyme systems, energy metabolism, etc. Al toxicity and Cu, Zn, and Se toxicity and deficiency can affect the immune system and following neuron inflammation and degeneration. These processes may result in MS pathology. Of course, factors such as lifestyle, environment, and industrialization can affect levels of trace elements in the human body.

Metalloimmunology: The metal ion-controlled immunity

Metals are essential components in all forms of life required for the function of nearly half of all enzymes and are critically involved in virtually all fundamental biological processes. Especially, the transition metals iron (Fe), zinc (Zn), manganese (Mn), nickel (Ni), copper (Cu) and cobalt (Co) are crucial micronutrients known to play vital roles in metabolism as well due to their unique redox properties. Metals carry out three major functions within metalloproteins: to provide structural support, to serve as enzymatic cofactors, and to mediate electron transportation. Metal ions are also involved in the immune system from metal allergies to nutritional immunity. Within the past decade, much attention has been drawn to the roles of metal ions in the immune system, since increasing evidence has mounted to suggest that metals are critically implicated in regulating both the innate immune sensing of and the host defense against invading pathogens. The importance of ions in immunity is also evidenced by the identification of various immunodeficiencies in patients with mutations in ion channels and transporters. In addition, cancer immunotherapy has recently been conclusively demonstrated to be effective and important for future tumor treatment, although only a small percentage of cancer patients respond to immunotherapy because of inadequate immune activation. Importantly, metal ion-activated immunotherapy is becoming an effective and potential way in tumor therapy for better clinical application. Nevertheless, we are still in a primary stage of discovering the diverse immunological functions of ions and mechanistically understanding the roles of these ions in immune regulation. This review summarizes recent advances in the understanding of metal-controlled immunity. Particular emphasis is put on the mechanisms of innate immune stimulation and T cell activation by the essential metal ions like calcium (Ca²⁺), zinc (Zn²⁺), manganese (Mn²⁺), iron (Fe²⁺/Fe³⁺), and potassium (K⁺), followed by a few unessential metals, in order to draw a general diagram of metalloimmunology.

Arid5a Regulation and the Roles of Arid5a in the Inflammatory Response and Disease

Abnormal gene expression patterns underlie many diseases that represent major public health concerns and robust therapeutic challenges. Posttranscriptional gene regulation by RNA-binding proteins (RBPs) is well-recognized, and the biological functions of RBPs have been implicated in many diseases, such as autoimmune diseases, inflammatory diseases, and cancer. However, a complete understanding of the regulation mediated by several RBPs is lacking. During the past few years, a novel role of AT-rich interactive domain-containing protein 5a (Arid5a) as an RBP is being investigated in the field of immunology owing to binding of Arid5a protein to the 3' untranslated region (UTR) of Il-6 mRNA. Indeed, Arid5a is a dynamic molecule because upon inflammation, it translocates to the cytoplasm and stabilizes a variety of inflammatory mRNA transcripts, including Il-6, Stat3, Ox40, T-bet, and IL-17-induced targets, and contributes to the inflammatory response and a variety of diseases. TLR4-activated NF-κB and MAPK pathways are involved in regulating Arid5a expression from synthesis to degradation, and even a slight alteration in these pathways can lead to intense production of inflammatory molecules, such as IL-6, which may further contribute to the development of inflammatory diseases such as sepsis and experimental autoimmune encephalomyelitis. This review highlights the regulation of the Arid5a expression and function. Additionally, recent findings on Arid5a are discussed to further our understanding of this molecule, which may be a promising therapeutic target for inflammatory diseases.

Micronutrients in autoimmune diseases: possible therapeutic benefits of zinc and vitamin D

A functional immune system is essential for healthy life. This is achieved by the coordinate activation and interaction of different immune cells. One should be aware that activation of the immune response is as important as its deactivation when the pathogens are cleared, as otherwise host tissue can be damaged up to life-threatening levels. Autoimmune diseases (AID) represent a phenomenon of immune cells attacking host cells and tissue. Five to eight percent of the world's population are currently affected by 80-100 AID. In recent years, the incidence has been constantly increasing, reaching alarmingly high numbers particularly for type 1 diabetes mellitus, Crohn's disease, rheumatoid arthritis, Sjogren's syndrome and multiple sclerosis. This indicates a higher societal burden of AID for the future. This article provides an overview of general concepts of triggers and underlying mechanisms leading to self-destruction. Lately, several original concepts of disease etiology were revised, and there is a variety of hypotheses on triggers, underlying mechanisms and preventive actions. This article concentrates on the importance of nutrition, especially zinc and vitamin D, for balancing the immune function. Homespun nutritional remedies seem to reenter today's therapeutic strategies. Current treatment approaches are largely symptomatic or suppress the immune system. However, recent studies reveal significant benefits of nutrition-related therapeutic approaches including prevention and treatment of established disease, which offer a cost-efficient and trigger-unspecific alternative addressing balancing rather than suppression of the immune system. Zinc and vitamin D are currently the best studied and most promising candidates for therapeutic intervention.