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.

Methionine restriction fundamentally supports health by tightening epithelial barriers.

Dietary methionine restriction (MR) has been found to affect one of the most primary tissue-level functions of an organism: the efficiency with which the epithelial linings of major organs separate the fluid compartments that they border. This process, epithelial barrier function, is basic for proper function of all organs, including the lung, liver, gastrointestinal tract, reproductive tract, blood-brain barrier, and kidney. Specifically, MR has been found to modify the protein composition of tight junctional complexes surrounding individual epithelial cells in a manner that renders the complexes less leaky. This has been observed in both a renal epithelial cell culture model and in gastrointestinal tissue. In both cases, MR increased the transepithelial electrical resistance across the epithelium, while decreasing passive leak of small nonelectrolytes. However, the specific target protein modifications involved were unique to each case. Overall, this provides an example of the primary level on which MR functions to modify, and improve, an organism.

Drug delivery of zinc to Barrett's metaplasia by oral administration to Barrett's esophagus patients.

BACKGROUND: Delivery of a pharmacologically effective drug dosage to a target tissue is critical. Barrett's epithelia are a unique challenge for drug delivery of orally administered zinc due to rapid transit down the esophageal lumen, incomplete absorptive differentiation of these epithelia, and the use of proton-pump inhibitor drugs abrogating intestinal uptake of supplemental zinc. METHODS: Barrett's esophagus patients were administered oral zinc gluconate (26 mg zinc twice daily) for 14 days prior to biopsy procurement. Barrett's biopsies were analyzed for total zinc content by atomic absorption spectroscopy and by western immunoblot for cellular proteins known to be regulated by zinc. RESULTS: Cellular levels of both the Znt-1 transport protein and the alpha isoform of PKC were over 50% lower in the zinc treatment group. CONCLUSION: Oral zinc administration can result in effective delivery of zinc to Barrett's epithelia with resulting effects on intracellular signal transduction.

Proton Pump Inhibitors Interfere With Zinc Absorption and Zinc Body Stores.

BACKGROUND: Proton pump inhibitors (PPIs) cause a sharp elevation of gastro-duodenal luminal pH which in turn has resulted in reports of reduced absorption of magnesium and certain other nutrients. METHODS: Gastroesophageal reflux disease (GERD) patients on long-term PPI therapy (> 6 months) or healthy test subjects (not on any acid preventive or neutralizing medication) were administered oral doses of zinc gluconate (26.2 mg zinc, twice daily) for 14 days followed by 5 cc venous blood samples. Plasma was analyzed for total zinc content by atomic absorption spectrophotometry. Baseline plasma and red blood cell zinc levels were also measured in these two groups when not taking any zinc supplementation. RESULTS: Plasma zinc levels of healthy controls increased by 126% during the period of zinc supplementation compared to only a 37% increase for individuals on long-term PPI therapy. On their normal diet (with no zinc supplementation), PPI-users had a 28% lower plasma zinc level than healthy controls (P < 0.005). CONCLUSIONS: PPI use dramatically reduces supplemental zinc uptake and can result in decreased zinc body stores. Certain individuals on long-term PPI therapy, such as infants being treated for colic, may be at risk for decreased systemic levels of trace metals needed for developmental, regenerative and immunological requirements.

Absence of Na+/sugar cotransport activity in Barrett's metaplasia.

AIM: To evaluate the presence of Na+-dependent, active, sugar transport in Barrett's epithelia as an intestinal biomarker, based on the well-documented, morphological intestinal phenotype of Barrett's esophagus (BE). METHODS: We examined uptake of the nonmeta-bolizable glucose analogue, alpha-methyl-D-glucoside (AMG), a substrate for the entire sodium glucose cotransporter (SGLT) family of transport proteins. During upper endoscopy, patients with BE or with uncomplicated gastroesophageal reflux disease (GERD) allowed for duodenal, gastric fundic, and esophageal mucosal biopsies to be taken. Biopsies were incubated in bicarbonate-buffered saline (KRB) containing 0.1 mmol/L 14C-AMG for 60 min at 20 centigrade. Characterized by abundant SGLT, duodenum served as a positive control while gastric fundus and normal esophagus, known to lack SGLT, served as negative controls. RESULTS: Duodenal biopsies accumulated 249.84+/-35.49 (SEM) picomoles AMG/microg DNA (n=12), gastric fundus biopsies 36.20+/-6.62 (n=12), normal esophagus 12.10+/-0.59 (n=3) and Barrett's metaplasia 29.79+/-5.77 (n=8). There was a statistical difference (P<0.01) between biopsies from duodenum and each other biopsy site but there was no statistically significant difference between normal esophagus and BE biopsies. 0.5 mmol/L phlorizin (PZ) inhibited AMG uptake into duodenal mucosa by over 89%, but had no significant effect on AMG uptake into gastric fundus, normal esophagus, or Barrett's tissue. In the absence of Na+ (all Na+ salts replaced by Li+ salts), AMG uptake in duodenum was decreased by over 90%, while uptake into gastric, esophageal or Barrett's tissue was statistically unaffected. CONCLUSION: Despite the intestinal enterocyte phenotype of BE, Na+-dependent, sugar transport activity is not present in these cells.