Human Enteric Defensins

Abstract

Paneth cells, secretory epithelial cells of the small intestinal crypts, are proposed to contribute to local host defense. Both mouse and human Paneth cells express a collection of antimicrobial proteins, including members of a family of antimicrobial peptides named defensins. In this study, data from an anchored polymerase chain reaction (PCR) strategy suggest that only two defensin mRNA isoforms are expressed in the human small intestine, far fewer than the number expressed in the mouse. The two isoforms detected by this PCR approach were human defensin family members, HD-5 and HD-6. The gene encoding HD-6 was cloned and characterized. HD-6 has a genomic organization similar to HD-5, and the two genes have a striking pattern of sequence similarity localized chiefly in their proximal 5'-flanking regions. Analysis of human fetal RNA by reverse transcriptase-PCR detected enteric defensin HD-5 mRNA at 13.5 weeks of gestation in the small intestine and the colon, but by 17 weeks HD-5 was restricted to the small intestine. HD-6 mRNA was detectable at 13.5-17 weeks of gestation in the small intestine but not in the colon. This pattern of expression coincides with the previously described appearance of Paneth cells as determined by ultrastructural approaches. Northern analysis of total RNA from small intestine revealed quantifiable enteric defensin mRNA in five samples from 19 24 weeks of gestation at levels approximately 40-250-fold less than those observed in the adult, with HD-5 mRNA levels greater than those of HD-6 in all samples. In situ hybridization analysis localized expression of enteric defensin mRNA to Paneth cells at 24 weeks of gestation, as is seen in the newborn term infant and the adult. Consistent with earlier morphological studies, the ratio of Paneth cell number per crypt was reduced in samples at 24 weeks of gestation compared with the adult, and this lower cell number partially accounts for the lower defensin mRNA levels as determined by Northern analysis. Low levels of enteric defensin expression in the fetus may be characteristic of an immaturity of local defense, which is thought to predispose infants born prematurely to infection from intestinal microorganisms.

Cdk2-dependent Phosphorylation of Homeobox Transcription Factor CDX2 Regulates Its Nuclear Translocation and Proteasome-mediated Degradation in Human Intestinal Epithelial Cells

“…Paneth cells are differentiated cells that exist in the crypt. However, CDX2 protein has been reported to be weakly expressed in adult mouse Paneth cells (41), and a negligible Paneth cell compartment is present in the mid-gestational human fetal jejunum (42). Determination of the net fluorescence intensity for 26 crypts from 8 fetal human jejuna confirmed that cells located in the lowest portion of the crypt expressed significantly (p Ͻ 0.05) lower levels of CDX2 that those located in the upper region of the crypt.…”

Clinical profile and outcome of early onset sepsis in high risk very low birth weight neonates

“…15 High culture positivity rate was seen in our study as preterm VLBW neonates are more susceptible to infection due to various reasons like lower levels of IgG which are passively transferred during the third trimester; mucous membrane defenses such as secretory immunoglobulin A (IgA), mucin, and defensins have been shown in some studies to be deficient in VLBW neonates and the first line of defense against infection is an intact epidermis and mucous membranes, which are compromised in VLBW infants. 4,[16][17][18] The most common risk factor associated with BACTEC blood culture positivity was prolonged rupture of membranes (PROM) with a positivity rate of 67% followed by urinary tract in infection in mother (58%). In the study done by Maharaja P et al low birth weight followed by PROM were the most common risk factors correlating to sepsis.…”

Inducible expression of an antibiotic peptide gene in lipopolysaccharide-challenged tracheal epithelial cells.

“…Oligonucleotides were radioactively labeled as described (13). PCR products were isolated and subcloned as described (14 (1 ,uM; Collaborative Research), and gentamycin (50 ,ug/ml). The complete medium was tested by the Limulus amebocyte lysate/gel clot assay to be free of bacterial endotoxin.…”