Immunohistochemical and Histoplanimetrical Study on the Spatial Relationship between the Settlement of Indigenous Bacteria and the Secretion of Bactericidal Peptides in Rat Alimentary Tract

Abstract

ABSTRACT. To clarify the regulatory mechanism by bactericidal peptides secretion, the secretion of bactericidal peptides was immunohistochemically and histoplanimetrically compared with the degree of Gram-positive/negative bacterial colonization throughout the rat alimentary tract. In the associated exocrine glands from the oral cavity to the stomach, no comparable differences were observed under the changes of development of indigenous bacterial colonies. In the small intestine, immunopositive granules for lysozyme and secretory phospholipase A2 (sPLA2) were markedly decreased, whereas immunopositive vacuoles in the Paneth cells were more increased at sites with hyper-development of indigenous bacterial colonies in the intervillous spaces than at sites with no or less development. No changes in exocrine glands were observed in the large intestine because of the constant existence of large quantities of bacteria. Gram-positive bacterial colonies on the mucosal surfaces were dominant from the oral cavity to the stomach. Gram-negative bacteria were dominant in the large intestine, and the distributions of both Gram-positive and negative bacteria were intermediate in the small intestine. These findings suggest that lysozyme and sPLA2 secreted from the Paneth cells contribute to the regulation of the proliferation of indigenous bacteria in the intervillous spaces of the small intestine, and that the inversion of distributions of Grampositive and -negative bacteria in the alimentary tract might be caused by the secretion of lysozyme and sPLA2 in the small intestine.KEY WORDS: alimentary tract, bactericidal peptides, digestive organs, indigenous bacteria, Paneth cells.

Immunohistochemical Detection of Toll-Like Receptor-2, -4 and -9 in Exocrine Glands Associated with Rat Alimentary Tract

“…TLR-2 recognizes both Gram-positive and -negative bacteria [37], because TLR-2 ligands such as peptidoglycan are contained in both. On the other hand, lysozyme and sPLA2 are transiently secreted from Paneth cells in the mucosa where indigenous bacteria hyper-proliferate into deeper intervillous spaces [40,41]. Therefore, a large amount of TLR-2 ligands are probably released from hyper-proliferated indigenous bacteria by the action of lysozyme in the intervillous spaces.…”

“…In the small intestine, the predominance of Gram-positive bacteria is irregularly changed to a predominance of Gram-negative bacteria [40]. Yokoo et al [40] hypothesize that this change of the predominance of Gram-positive bacteria might be caused by the transient secretion of lysozymes and sPLA2 from Paneth cells under hyper-proliferation of indigenous bacteria.…”

“…Indigenous bacteria proliferate from the apical portions of the intestinal villi into the intervillous spaces in the rat small intestine [38]. The proliferation of indigenous bacteria in the intervillous spaces leads to various host responses, such as the reduction of villous height, the acceleration of the epithelial cell migration [31], and the transient secretion of lysozyme and soluble phospholipase A2 (sPLA2) from Paneth cells [40,41]. From these findings, it has been speculated that special membrane receptors for the detection of indigenous bacterial proliferation exist on the surfaces of the intestinal villi in the rat small intestine.…”

Histoplanimetrical Study on the Relationship between Invasion of Indigenous Bacteria into Intestinal Crypts and Proliferation of Epithelial Cells in Rat Ascending Colon

“…In the previous studies, the secretions of lysozyme and secretory phospholipase A2 from Paneth cells [38] and the acceleration of epithelial cell migration [26] are induced in the local sites with bacterial hyper-proliferations in the rat ileum. From these findings, stable bacterial settlement is speculated to be maintained by the balance between the bacterial proliferation and the elimination of bacteria by host defense in the rat small intestine.…”

“…Additionally, numerous indigenous bacteria exist between the mucosal folds in the rat ascending colon [27]. However, the detailed distribution of the settlement sites of indigenous bacteria has not been investigated in the ascending colon.The settlement of indigenous or exogenous bacteria is regulated by various host defense, such as digestive enzymes, bactericidal peptides, physical elimination of epithelial cells and so on [7,14,15,17,37,38]. In the previous studies, the secretions of lysozyme and secretory phospholipase A2 from Paneth cells [38] and the acceleration of epithelial cell migration [26] are induced in the local sites with bacterial hyper-proliferations in the rat ileum.…”