The protective effect of oleanolic acid on NMDA-induced MLE-12 cells apoptosis and lung injury in mice by activating SIRT1 and reducing NF-κB acetylation.

Overactivation of the N-methyl-d-aspartate (NMDA) receptor promotes oxidative stress, aggravates the inflammatory response and induces excitotoxic lung injury. NMDA is a synthetic agonist that selectively activates the NMDA receptor. Oleanolic acid (OA) is a natural anti-inflammatory and antioxidant compound. This study investigated the effect and possible mechanism of OA on NMDA-induced acute lung injury (ALI) in mice. OA pretreatment alleviated NMDA-induced histological lung changes and ameliorated pulmonary oedema and pulmonary permeability. At the same time, OA inhibited inflammatory cell infiltration and decreased the levels of tumour necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1ß in the lung and bronchoalveolar lavage fluid (BALF). OA markedly decreased malondialdehyde (MDA) production and increased the superoxide dismutase (SOD) and glutathione (GSH) contents of the lung in vivo. Meanwhile, we first found that NMDA increased LDH activity and decreased cell viability, and induced oxidative stress and apoptosis in mouse lung epithelial (MLE)-12 cells. By employing SRT1720 and sirtinol, the activator and inhibitor of sirtuin 1 (SIRT1), we found that SRT1720 partially eliminated the increase in ROS，and sirtinol further promoted the increase in ROS caused by NMDA. OA increased MLE-12 cells viability and attenuated oxidative stress after NMDA challenge in vitro. OA suppressed NMDA-induced MLE-12 cells apoptosis, while sirtinol inhibited the effect of OA. In addition, OA significantly upregulated the levels of SIRT1, nuclear-related factor 2(Nrf2) and Bcl-2 protein and downregulated the levels of acetylated nuclear factor-kappa B (NF-κB), NLRP3 and Bax protein. In conclusion, OA attenuated NMDA-induced excitotoxic lung injury, potentially through its anti-inflammatory, antioxidative stress and anti-apoptotic effects. The mechanism may be related to activating SIRT1 and reducing NF-κB acetylation.

An excessive increase in glutamate contributes to glucose-toxicity in ß-cells via activation of pancreatic NMDA receptors in rodent diabetes.

In the nervous system, excessive activation of NMDA receptors causes neuronal injury. Although activation of NMDARs has been proposed to contribute to the progress of diabetes, little is known about the effect of excessive long-term activation of NMDARs on ß-cells, especially under the challenge of hyperglycemia. Here we thoroughly investigated whether endogenous glutamate aggravated ß-cell dysfunction under chronic exposure to high-glucose via activation of NMDARs. The glutamate level was increased in plasma of diabetic mice or patients and in the supernatant of ß-cell lines after treatment with high-glucose for 72 h. Decomposing the released glutamate improved GSIS of ß-cells under chronic high-glucose exposure. Long-term treatment of ß-cells with NMDA inhibited cell viability and decreased GSIS. These effects were eliminated by GluN1 knockout. The NMDAR antagonist MK-801 or GluN1 knockout prevented high-glucose-induced dysfunction in ß-cells. MK-801 also decreased the expression of pro-inflammatory cytokines, and inhibited I-κB degradation, ROS generation and NLRP3 inflammasome expression in ß-cells exposed to high-glucose. Furthermore, another NMDAR antagonist, Memantine, improved ß-cells function in diabetic mice. Taken together, these findings indicate that an increase of glutamate may contribute to the development of diabetes through excessive activation of NMDARs in ß-cells, accelerating ß-cells dysfunction and apoptosis induced by hyperglycemia.

Endogenous hydrogen sulfide mediates the cardioprotection induced by ischemic postconditioning in the early reperfusion phase.

Hydrogen sulfide (H(2)S), produced by cystanthionine-γ-lysase (CSE) in the cardiovascular system, has been suggested to be the third gasotransmitter in addition to nitric oxide (NO) and carbon monoxide (CO). The present study aimed to investigate the role of H(2)S in ischemic postconditioning (IPO) during the early period of reperfusion. IPO with 6 episodes of 10 sec reperfusion followed by 6 episodes of 10 sec ischemia (IPO 2') was administered when reperfusion was initiated. Cardiodynamics and the concentration of H(2)S were measured at 1, 2, 3, 4, 5, 10, 20, 30, 60, 90 and 120 min of reperfusion. Lactate dehydrogenase (LDH) levels and infarct size were determined at the end of the reperfusion. The concentration of H(2)S was stable during the whole experiment in the control group, whereas it reached a peak at the first minute of reperfusion in the ischemia-reperfusion (IR) group. The concentration of H(2)S at the first minute of reperfusion in the IPO 2' group was higher compared to that of the IR group, which correlated with cardioprotection including improved heart contractile function and reduced infarct size and LDH levels. However, the above effects of IPO 2' were attenuated by pre-treatment with blockade of endogenous H(2)S production with DL-propargylglycine for 20 min prior to global ischemia. Furthermore, we found that other forms of IPO, IPO commencing at 1 min after reperfusion (delayed IPO) or lasting only for 1 min (IPO 1'), failed to increase the concentration of H(2)S and protect the myocardium. We conclude that the peak of endogenous H(2)S in the early reperfusion phase is the key to cardioprotection induced by IPO.

[Progress in prolactin receptor research].

Prolactin (PRL) is secreted by lactotrophs in the anterior pituitary and some extra-pituitary tissues such as breast, lacrimal gland, uterus, thymus and spleen, etc. Since PRL is closely related to growth hormone (GH) and placental lactogens (PL), it has been broadly accepted that PRL, GH and PL are resulted from the duplication of an ancestral gene. PRL regulates hundreds of biological functions by endocrine, paracrine and autocrine manners. Prolactin initiates its effects by binding to its receptor (PRLR). PRLR belongs to the class I cytokine receptor superfamily. Up to now, three membrane--PRLRs have been clarified. They are long form (LF), intermediate form (IF) and short form (SF) including SFla and SFlb. All PRLRs are derived from a primary transcript of common gene through alternative splicing mechanism. Although the extracellular domain (ECD) and the transmembrane domain (TD) of LF, IF and SF are equal, different isoforms of PRLR exert different function through different intracellular domain. It has been well documented that abnormity of PRLR is closely related to the pathogenesis, progression and prognosis of cancers including breast cancer. Several PRLR antagonists have been well designed and evidenced to have the potential to be important therapeutics.