What Is Zinc?
Zinc is an essential mineral critical for a wide array of cellular metabolic activities. It plays a significant role in regulating the catabolic activities of numerous enzymes, enhancing immune functions, promoting wound healing, and facilitating protein and DNA synthesis.
Additionally, zinc is involved in cell signaling and division. This vital mineral can be found naturally in certain foods, such as meat, fish, and seafood. It is also available as a dietary supplement and is an ingredient in some over-the-counter medications for colds and denture adhesive creams.
In clinical settings, the estimation of zinc levels in serum or plasma is typically conducted to determine the body’s zinc status. The normal physiological level of zinc in human serum or plasma ranges from 80 to 120 mcg/cL. Zinc deficiency is characterized by zinc levels below 70 mcg/dL in women and 74 mcg/dL in men.
The Link Between Zinc and Immune Health
Zinc is indispensable for the normal development and functioning of various immune cells, including T cells, B cells, neutrophils, macrophages, and natural killer (NK) cells. A deficiency in zinc can potentially increase the risk of infections and cause severe immune dysfunctions.
Zinc plays a crucial role in regulating cytokine production and suppressing inflammation. Its broad-spectrum antioxidant properties inhibit the production of reactive oxygen species (ROS) and prevent oxidative damage to cellular macromolecules.
In its positively charged ionic form, zinc acts as a chemo-attractant, channeling pathogens for phagocytosis and subsequently destroying them through ROS production. Zinc can inhibit the uptake of manganese by Streptococcus pneumoniae through competitive binding, which impairs the bacteria’s ability to invade and infect host cells.
Zinc acts as a catalyst, structural component, or regulatory ion in various immune processes. It boosts the immune system by enhancing the activities of both innate immune cells (neutrophils and NK cells) and adaptive immune cells (B cells and T cells).
Zinc is vital for neutrophil development and activation, and zinc deficiency has been shown to reduce neutrophils’ ability to destroy pathogens through ROS-mediated phagocytosis. Moreover, zinc supplementation can reduce neutrophil recruitment and subsequently prevent lung injury.
Regarding NK cells, zinc plays a critical role in their development, maturation, and function. Zinc supplementation has been found to induce the differentiation of CD34+ cells into NK cells and increase the cytotoxic functions of NK cells.
For adaptive immune cells, a positive correlation has been observed between intracellular zinc levels and the activation and proliferation of B cells. Zinc deficiency affects the development of immature and premature B cells and subsequent antibody production.
Zinc also impacts the growth and functions of T cells. It regulates the activation of mature T cells by interacting with protein kinase C and lymphocyte protein tyrosine kinase. Zinc deficiency during T cell maturation can increase pre-T cell apoptosis.
A reduction in zinc levels can lead to thymus atrophy and T cell lymphopenia. A reduced zinc level is associated with a decreased type 1 to type 2-helper cell ratio, reduced interferon-gamma production, and compromised T-cell-mediated immune response. Conversely, zinc supplementation has been found to enhance cellular and humoral immunity and reduce chronic inflammation.
Zinc ions act as second messengers to modulate various immune signaling pathways. They induce monocytes to produce pro-inflammatory cytokines, vital for regulating immune and inflammatory responses to infections. Zinc increases the production of interleukin 2 (IL-2) by T cells, essential for the growth, proliferation, and differentiation of naïve T cells into effector T cells. Zinc supplementation helps restore the balance between type 1 and type 2 T-helper cells by modulating cytokine production.
Zinc and Wound Healing
Wound healing is a natural physiological response to tissue injury. It is crucial for restoring the protective epithelial barrier and regaining tissue volume and strength. The wound healing process is closely related to inflammatory and immune responses, with zinc playing a vital role through its immunomodulatory functions. Zinc deficiency has been found to delay the wound healing process.
Significant health benefits of zinc supplementation have been observed in critically ill patients, those with severe burn injuries, subcutaneous abscesses, minor surgery patients, and those with pressure ulcers.
Zinc is essential in every phase of the wound healing process. The primary functions of zinc during wound healing include bacterial clearance, tissue necrosis, resolution of inflammation, removal of tissue debris, fibroblast and keratinocyte influx and subsequent re-epithelization, angiogenesis, stem cell activation, and remodeling of the extracellular matrix.
Zinc supplementation in individuals with zinc deficiency has shown beneficial effects on wound healing. However, studies investigating the impact of zinc supplementation on wound healing in patients without zinc deficiency have produced mixed results.
Topical zinc sulfate formulations are widely used in wound care for their antioxidant effects. Highly insoluble zinc oxide is also used in wound care due to its ability to supply zinc wounds for a prolonged period and to increase collagen degradation in necrotic wounds. Daily dietary zinc supplementation is a routine practice in severe burn care.
In recent years, zinc oxide nanoparticles have garnered significant attention for wound healing due to their effective cell penetration, immunomodulation, and antimicrobial capacity. These nanoparticles represent a promising advancement in the field of wound care, potentially improving outcomes for patients with severe injuries and chronic wounds.
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