Fe3+ opposes the 1,25(OH)2D3-induced calcium transport across intestinal epithelium-like Caco-2 monolayer in the presence or absence of ascorbic acid

Alterations in trace elements and cation profiles in transfusion-dependent thalassemia patients

BACKGROUND

Transfusion-dependent thalassemia (TDT) is a severe form of beta-thalassemia, characterized by defective-globin production, resulting in a buildup of unpaired alpha globin chains. Patients with TDT can only survive if they receive safe blood transfusions regularly, which causes iron overload in their blood, which causes a variety of disorders. Cations and trace elements in TDT patients as a drug target deserve more studies.

OBJECTIVES

In the present study, the cations and some trace elements were studied in TDT patients as a tool to adjust their level in the case of any disturbances.

METHODS

Serum calcium, magnesium, zinc, copper, and iron were measured spectrophotometrically while manganese and cobalt were measured by flameless atomic absorption spectroscopy in 100 TDT patients and compared with 35 healthy control children.

RESULTS

Patients with TDT exhibit a notable elevation in blood levels of iron, copper, copper/zinc ratio, and manganese, with a substantial reduction in serum levels of zinc, magnesium, calcium, and cobalt, as compared to the control group. These minerals have diverse associations with clinical data and transfusion frequencies. The receiver operating characteristic (ROC) analysis revealed that the elevated levels of iron, manganese, and calcium exhibit the greatest diagnostic capability, with a sensitivity and specificity of over 80 %, and a Youdin's J value of more than 0.6.

CONCLUSION

The levels of cations and trace elements are disturbed in TDT patients. Hence, the monitoring and adjustment of the level of these minerals are important to prevent further consequences.

Vasoactive intestinal peptide and cystic fibrosis transmembrane conductance regulator contribute to the transepithelial calcium transport across intestinal epithelium-like Caco-2 monolayer

Vasoactive intestinal peptide (VIP) as a neurocrine factor released by enteric neurons has been postulated to participate in the regulation of transcellular active calcium transport across intestinal epithelium, but the preceding evidence is scant and inconclusive. Herein, transepithelial calcium flux and epithelial electrical parameters were determined by Ussing chamber technique with radioactive tracer in the intestinal epithelium-like Caco-2 monolayer grown on Snapwell. After 3-day culture, Caco-2 cells expressed mRNA of calcium transporters, i.e., TRPV6, calbindin-D_9k, PMCA_1b and NCX1, and exhibited transepithelial resistance of ~200 Ω cm², a characteristic of leaky epithelium similar to the small intestine. VIP receptor agonist was able to enhance transcellular calcium flux, whereas VIP receptor antagonist totally abolished calcium fluxes induced by 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃]. Since the intestinal cystic fibrosis transmembrane conductance regulator (CFTR) could be activated by VIP and calciotropic hormones, particularly parathyroid hormone, we sought to determine whether CFTR also contributed to the 1,25(OH)₂D₃-induced calcium transport. A selective CFTR inhibitor (20–200 μM CFTR_inh-172) appeared to diminish calcium fluxes as well as transepithelial potential difference and short-circuit current, both of which indicated a decrease in electrogenic ion transport. On the other hand, 50 μM genistein—a molecule that could rapidly activate CFTR—was found to increase calcium transport. Our in silico molecular docking analysis confirmed direct binding of CFTR_inh-172 and genistein to CFTR channels. In conclusion, VIP and CFTR apparently contributed to the intestinal calcium transport, especially in the presence of 1,25(OH)₂D₃, thereby supporting the existence of the neurocrine control of intestinal calcium absorption.