Calcitriol modifies tight junctions, improves barrier function, and reduces TNF‐α‐induced barrier leak in the human lung‐derived epithelial cell culture model, 16HBE 14o‐

Abstract Using the 16HBE 14o‐ human airway epithelial cell culture model, calcitriol (Vitamin D) was shown to improve barrier function by two independent metrics – increased transepithelial electrical resistance (TER) and reduced transepithelial diffusion of 14C‐D‐mannitol (Jm). Both effects were concentration dependent and active out to 168 h post‐treatment. Barrier improvement associated with changes in the abundance of specific tight junctional (TJ) proteins in detergent‐soluble fractions, most notably decreased claudin‐2. TNF‐α‐induced compromise of barrier function could be attenuated by calcitriol with a concentration dependence similar to that observed for improvement of control barrier function. TNF‐α‐induced increases in claudin‐2 were partially reversed by calcitriol. The ERK 1,2 inhibitor, U0126, itself improved 16HBE barrier function indicating MAPK pathway regulation of 16HBE barrier function. Calcitriol's action was additive to the effect of U0126 in reducing TNF‐ α ‐induced barrier compromise, suggesting that calcitriol may be acting through a non‐ERK pathway in its blunting of TNF‐ α – induced barrier compromise. This was supported by calcitriol being without effect on pERK levels elevated by the action of TNF‐α. Lack of effect of TNF‐ α on the death marker, caspase‐3, and the inability of calcitriol to decrease the elevated LC3B II level caused by TNF‐α, suggest that calcitriol's barrier improvement does not involve a cell death pathway. Calcitriol's improvement of control barrier function was not additive to barrier improvement induced by retinoic acid (Vitamin A). Calcitriol improvement and protection of airway barrier function could in part explain Vitamin D's reported clinical efficacy in COVID‐19 and other airway diseases

Zinc reduces epithelial barrier compromise induced by human seminal plasma.

Human semen has the potential to modulate the epithelial mucosal tissues it contacts, as seminal plasma (SP) is recognized to contain both pro- and anti-barrier components, yet its effects on epithelial barrier function are largely unknown. We addressed the role of human SP when exposed to the basal-lateral epithelial surface, a situation that would occur clinically with prior mechanical or disease-related injury of the human epithelial mucosal cell layers in contact with semen. The action of SP on claudins-2, -4, -5, and -7 expression, as well as on a target epithelium whose basolateral surface has been made accessible to SP, showed upregulation of claudins-4 and -5 in CACO-2 human epithelial cell layers, despite broad variance in SP-induced modulation of transepithelial electrical resistance and mannitol permeability. Upregulation of claudin-2 by SP also exhibited such variance by SP sample. We characterize individual effects on CACO-2 barrier function of nine factors known to be present abundantly in seminal plasma (zinc, EGF, citrate, spermine, fructose, urea, TGF, histone, inflammatory cytokines) to establish that zinc, spermine and fructose had significant potential to raise CACO-2 transepithelial resistance, whereas inflammatory cytokines and EGF decreased this measure of barrier function. The role of zinc as a dominant factor in determining higher levels of transepithelial resistance and lower levels of paracellular leak were confirmed by zinc chelation and exogenous zinc addition. As expected, SP presentation to the basolateral cell surface also caused a very dramatic yet transient elevation of pErk levels. Results suggest that increased zinc content in SP can compete against the barrier-compromising effect of negative modulators in SP when SP gains access to that epithelium's basolateral surface. Prophylactic elevation of zinc in an epithelial cell layer prior to contact by SP may help to protect an epithelial barrier from invasion by SP-containing STD microbial pathogens such as HPV or HIV

Micronutrient Improvement of Epithelial Barrier Function in Various Disease States: A Case for Adjuvant Therapy

The published literature makes a very strong case that a wide range of disease morbidity associates with and may in part be due to epithelial barrier leak. An equally large body of published literature substantiates that a diverse group of micronutrients can reduce barrier leak across a wide array of epithelial tissue types, stemming from both cell culture as well as animal and human tissue models. Conversely, micronutrient deficiencies can exacerbate both barrier leak and morbidity. Focusing on zinc, Vitamin A and Vitamin D, this review shows that at concentrations above RDA levels but well below toxicity limits, these micronutrients can induce cell- and tissue-specific molecular-level changes in tight junctional complexes (and by other mechanisms) that reduce barrier leak. An opportunity now exists in critical care—but also medical prophylactic and therapeutic care in general—to consider implementation of select micronutrients at elevated dosages as adjuvant therapeutics in a variety of disease management. This consideration is particularly pointed amidst the COVID-19 pandemic

The Host Microbiome Regulates and Maintains Human Health: A Primer and Perspective for Non-Microbiologists

Humans consider themselves discrete autonomous organisms, but recent research is rapidly strengthening the appreciation that associated microorganisms make essential contributions to human health and well being. Each person is inhabited and also surrounded by his/her own signature microbial cloud. A low diversity of microorganisms is associated with a plethora of diseases, including allergy, diabetes, obesity, arthritis, inflammatory bowel diseases, and even neuropsychiatric disorders. Thus, an interaction of microorganisms with the host immune system is required for a healthy body. Exposure to microorganisms from the moment we are born and appropriate microbiome assembly during childhood are essential for establishing an active immune system necessary to prevent disease later in life. Exposure to microorganisms educates the immune system, induces adaptive immunity, and initiates memory B and T cells that are essential to combat various pathogens. The correct microbial-based education of immune cells may be critical in preventing the development of autoimmune diseases and cancer. This review provides a broad overview of the importance of the host microbiome and accumulating knowledge of how it regulates and maintains a healthy human system

Remodeling of Tight Junctions and Enhancement of Barrier Integrity of the CACO-2 Intestinal Epithelial Cell Layer by Micronutrients.

The micronutrients zinc, quercetin, butyrate, indole and berberine were evaluated for their ability to induce remodeling of epithelial tight junctions (TJs) and enhance barrier integrity in the CACO-2 gastrointestinal epithelial cell culture model. All five of these chemically very diverse micronutrients increased transepithelial electrical resistance (Rt) significantly, but only berberine also improved barrier integrity to the non-electrolyte D-mannitol. Increases of Rt as much as 200% of untreated controls were observed. Each of the five micronutrients also induced unique, signature-like changes in TJ protein composition, suggesting multiple pathways (and TJ arrangements) by which TJ barrier function can be enhanced. Decreases in abundance by as much as 90% were observed for claudin-2, and increases of over 300% could be seen for claudins -5 and -7. The exact effects of the micronutrients on barrier integrity and TJ protein composition were found to be highly dependent on the degree of differentiation of the cell layer at the time it was exposed to the micronutrient. The substratum to which the epithelial layer adheres was also found to regulate the response of the cell layer to the micronutrient. The implications of these findings for therapeutically decreasing morbidity in Inflammatory Bowel Disease are discussed

Sample-to-sample variation in Interleukin-8 (A) and zinc (B) concentrations in seminal plasma.

<p>Seminal plasma was diluted 1:20 in culture medium. IL-8 and zinc levels were measured as described in Materials and Methods. Each bar is the average of two (IL-8) or five (zinc) measurements with a variation of less than 5% of the mean.</p

Summary of effects of specific seminal plasma components on CACO-2 cell layer barrier function.

<p>Summary of effects of specific seminal plasma components on CACO-2 cell layer barrier function.</p

Specific Components of Seminal Plasma in Substantial Excess Relative to Blood Plasma

<p>Specific Components of Seminal Plasma in Substantial Excess Relative to Blood Plasma</p