Mechanism of Action
With zinc playing a prominent role in many major processes within the human body, its mechanism of action varies depending on the organ system as well as the relevant process involved.
Immune System and Anti-Inflammation
In the immune system, zinc functions as a second messenger for immune cells; intracellular zinc participates in signaling events in immunity. It is involved in the development of monocytes and macrophages and regulates macrophagic functions such as phagocytosis and the production of proinflammatory cytokines. Zinc also inhibits phosphodiesterase, resulting in increased levels of guanosine-3′ 5′- cyclic monophosphate which leads to the suppression of Tumor Necrosis Factor alpha (TNF-a), interleukin-1 beta (IL-1B), as well as other inflammatory cytokines. Additionally, zinc increases the expression of peroxisome proliferator-activated receptor- alpha; this results in the downregulation of inflammatory cytokines and adhesion molecules. Due to these and several other actions in the immune system, zinc is considered to be a key anti-inflammatory agent in the human body.
Zincs Effect on Skin
In the skin, zinc exerts its effects through several means in the development and maintenance of the skin cells. Zinc is most concentrated in the stratum spinosum layer of the skin compared to the other three layers namely basal layer, stratum granulosum, and stratum corneum. Studies have shown that zinc facilitates the proliferation as well as the survival of keratinocytes in the stratum spinosum; it also suppressed the activation of interferon-gamma and tumor necrosis factor-alpha by these keratinocytes. Additionally, zinc plays an active role in the development of Langerhans cells, a type of antigen-presenting cells, within the skin. Furthermore, the expression of melanocytes in the human skin is facilitated by zinc through mechanisms that are not yet fully understood.
Central Nervous System
In the central nervous system, zinc is essential in the formation and development of the growth factors, hormones, enzymes, and proteins during neurodevelopment; mild zinc deficiency during pregnancy has been shown to result in learning and memory abnormalities. Zinc helps in the development of the neural tube, the first brain structure that develops during pregnancy, the neural crest, and the process of stem cell proliferation during neurogenesis. Furthermore, free zinc is found in synaptic vesicles where it acts to modulate a variety of postsynaptic receptors; in the synaptic cleft it reduces the inhibitory actions of GABA receptors. Free zinc also exerts inhibitory actions on the release of glutamate, an excitatory neurotransmitter.