L-Arginine improves DNA synthesis in LPS-challenged enterocytes

Abstract

The neonatal small intestine is susceptible to damage by endotoxin, and this cytotoxicity may involve intracellular generation of reactive oxygen species (ROS), resulting in DNA damage and mitochondrial dysfunction. L-Arginine (Arg) confers a cytoprotective effect on lipopolysaccharide (LPS)-treated enterocytes through activation of the mammalian target of the rapamycin (mTOR) signaling pathway. Arg improves DNA synthesis and mitochondrial bioenergetics, which may also be responsible for beneficial effects of Arg on intestinal mucosal cells. In support of this notion, results of recent studies indicate that elevated Arg concentrations enhances DNA synthesis, cell-cycle progression, and mitochondrial bioenergetics in LPS-treated intestinal epithelial cells through mechanisms involving activation of the PI3K-Akt pathway. These findings provide a biochemical basis for dietary Arg supplementation to improve the regeneration and repair of the small-intestinal mucosa in both animals and humans.

N-Acetyl-L-cysteine Protects the Enterocyte against Oxidative Damage by Modulation of Mitochondrial Function

“…Mitochondria are the powerhouses of the cell, producing a considerable share of cellular ATP and playing a central role in cellular function and metabolism [28]. Our previous report showed that mitochondrial dysfunction was observed with decrease in the basal respiration, maximal respiration, and nonmitochondrial respiration after LPS treatment [1]. The present data also demonstrated that mitochondrial function damage induced by H 2 O 2 was observed, showing decrease in basal respiration, proton leak, maximal respiration, spare respiratory capacity, nonmitochondrial respiration, and ATP production.…”

“…DNA synthesis during cell proliferation in all treatment groups was quantified using 5-ethynyl-2′-deoxyuridine (EdU; Invitrogen) incorporation using Cell-Light EdU Kit (Rui Bo Biotechnology Limited Company, Guangzhou, China), as described in our previous studies [1]. Briefly, IPEC-J2 cells were cultured in DMEM-H mediums containing 50  μ M EdU for 1 h. An Olympus BX51 microscope (Olympus, Japan) was used to observe EdU-positive cells.…”

“…The spare respiratory capacity was represented by the maximal respiratory capacity subtracted from the baseline oxygen consumption rate (OCR). The residual oxygen consumption that occurred after addition of rotenone and antimycin A was ascribed to nonmitochondrial respiration and was subtracted from all measured values in the analysis [1]. Owing to the effects of NAC on IPEC-J2 proliferation, total cellular protein was determined and used to normalize mitochondrial respiration rates.…”

“…Protein concentrations of cell homogenates were measured using the BCA method and bovine serum albumin as standard, as described by our previous studies [1]. All samples were adjusted to an equal concentration.…”

“…The neonatal small intestine is particularly vulnerable to damage induced by endotoxin, and this damage may be involved in plasma and intracellular production of reactive oxygen species (ROS), resulting in cell apoptosis, reducing antioxidative capacity and mitochondrial dysfunction [1–3]. The intestinal epithelium, the border between the body and the environment, is the main place to transport the nutrient.…”