Vitamin D enhances reactive oxygen intermediates production in phagocytic cells in term and preterm infants

Newborn infants are endotoxin tolerant which may be responsible for their increased susceptibility to bacterial sepsis. Vitamin D has an immunomodulatory effect and newborn infants are at risk of vitamin D deficiency. We examined the in vitro effect of 1, 25-dihydroxyvitamin D (1,25OHD) on whole blood phagocytic toll-like receptor 4 (TLR4), CD11b, and reactive oxygen intermediates (ROIs) in newborn infants during sepsis.

Whole blood from preterm infants <32-wk gestation, control term neonates, and adults were sampled for phagocytic expression of ROI, TLR4, CD11b in response to lipopolysaccharide (LPS), and 1,25OHD using flow cytometer.

ROI production from newborn phagocytes incubated with LPS alone was decreased. Pretreatment with 1,25OHD demonstrated increased (P = 0.001) phagocytic ROI production in newborns but not in adults. 1,25OHD did not have any effect on TLR4 and CD11b in both newborns and adults. Pretreatment with ROI inhibitors (apocynin (APO) and diphenyleneiodonium), phosphoinositide 3-kinase (PI3K) inhibitor, and p38 inhibitor blocked neutrophil ROI production.

Neonatal phagocytic cells had diminished ROI production in the presence of LPS, however, pretreatment with 1,25OHD reversed this hyporesponsiveness. This action by 1,25OHD was mediated by activation of nicotinamide adenine dinucleotide phosphate oxidase system through PI3K signaling enzymes.