Pulses of cell Ca(2+) and the dynamics of tight junction opening and closing

Promoting effect of the Maillard reaction products produced during the stir-frying process of Hordei Fructus Germinatus on the intestinal absorption of active ingredients in Hordei Fructus Germinatus

This study was designed to evaluate the absorption promoting capacity of Maillard Reaction Products (MRPs) produced during the stir-frying process of Hordei Fructus Germinatus on catechin, ferulic acid, quercetin and kaempferol by the ex vivo rat everted gut sac model, in situ single-pass intestinal perfusion model and the whole animal model. Moreover, verapamil, EDTA and mannitol were used for determining the transport mechanism of catechin, ferulic acid, quercetin and kaempferol. The tight junction (TJ) proteins including zonula occudens-1(ZO-1) and claudin-1 were chosen to investigate the promoting mechanism of MRPs by quantitative real-time PCR (qRT-PCR) and western blot analyses. The results showed that the MRPs produced during the stir-frying process of Hordei Fructus Germinatus could improve the intestinal absorption of catechin, ferulic acid, quercetin and kaempferol. And the absorption-promoting effect of MRPs was related to chelating effect and the reduced expression of claudin-1 and ZO-1. Our results suggested that MRPs could be promising oral absorption promoters, which might be another processing mechanism of Hordei Fructus Germinatus.

Homeostasis of the Intraparenchymal-Blood Glutamate Concentration Gradient: Maintenance, Imbalance, and Regulation

It is widely accepted that glutamate is the most important excitatory neurotransmitter in the central nervous system (CNS). However, there is also a large amount of glutamate in the blood. Generally, the concentration gradient of glutamate between intraparenchymal and blood environments is stable. However, this gradient is dramatically disrupted under a variety of pathological conditions, resulting in an amplifying cascade that causes a series of pathological reactions in the CNS and peripheral organs. This eventually seriously worsens a patient’s prognosis. These two “isolated” systems are rarely considered as a whole even though they mutually influence each other. In this review, we summarize what is currently known regarding the maintenance, imbalance and regulatory mechanisms that control the intraparenchymal-blood glutamate concentration gradient, discuss the interrelationships between these systems and further explore their significance in clinical practice.

Oxidative stress-induced disruption of epithelial and endothelial tight junctions

Mounting body of evidence indicates that the disruption of epithelial tight junctions and resulting loss of barrier function play a crucial role in the pathogenesis of a variety of gastrointestinal, hepatic, pulmonary, kidney and ocular diseases. Increased production of inflammatory mediators such as cytokines and reactive oxygen species disrupt the epithelial and endothelial barrier function by destabilizing tight junctions. Oxidative stress induced by various reactive oxygen species such as hydrogen peroxide, nitric oxide, peroxynitrite and hypochlorous acid disrupt the epithelial and endothelial tight junctions in various tissues. The mechanism involved in oxidative stress-induced disruption of tight junction includes protein modification such as thiol oxidation, phosphorylation, nitration and carbonylation. The role of signaling molecules such as protein kinases and protein phosphatases in regulation of tight junctions is discussed in this article. Understanding such mechanisms in oxidative stress-induced disruption of epithelial and endothelial barrier functions is likely to provide insight into the pathogenesis of various inflammatory diseases, and may form a basis for the design of treatment strategies for different diseases.