Cytoprotective actions of 2,4-dimethoxybenzylidene anabaseine in differentiated PC12 cells and septal cholinergic neurons

The potential cytoprotective actions of a novel nicotinic agent 2,4-dimethoxybenzilidene anabaseine (DMXB) were investigated in differentiated PC12 cells and transected rat septal cholinergic neurons in vivo. In NGF-differentiated PC12 cells, removal of both NGF and serum led to cell loss, a reduced % of cells expressing neurites, the release of lactate dehydrogenase, and a decrease in total cellular protein. Cell loss was apparent within 24 h, and remained constant between 4–8 days post-NGF removal. NGF alone (100 ng/ml), DMXB (10 μM), but not nicotine (10 μM), prevented these cell and neurite losses. DMXB-induced cytoprotection was blocked by 1 μM mecamylamine. DMXB (1 mg/kg, ip) injected twice but not once per day protected cholinesterase-staining septal neurons from retrograde degeneration following unilateral fimbrial transections. The twice per day DMXB injection-protocol also decreased cell roundness among cholinesterase-staining cells in the lesioned septal hemisphere compared to saline-injected animals. These studies suggest that DMXB may exert cytoprotective activity in NGF-sensitive neuronal populations. © 1994 Wiley-Liss, Inc.     

Effect of amyloid peptides on the increase in TrkA receptor expression induced by nicotine in vitro and in vivo

The ability of nicotine to induce a cytoprotective or neuroprotective action occurs through several down-stream mechanisms. One possibility is that the drug increases the expression of tyrosine kinase A (TrkA) nerve growth factor (NGF) receptors. Certain β-amyloid peptides (e.g., Aβ1–42) have been shown to bind with high affinity to α7 nicotinic receptors and thus interfere with a potentially neurotrophic influence. Treatment of differentiated PC-12 cells with nicotine produced a concentration-dependent increase in cell-surface TrkA receptors that occurred concomitantly with cytoprotection. The effect of nicotine was blocked by either of the α7 receptor antagonists α-bungarotoxin (α-BTX) or methyllycaconatine. The cytoprotective action of nicotine also was inhibited by pretreatment with 10–100 nM Aβ1–42. Nicotine also was administered (four injections of 30 μg, spaced evenly over 24 h) to rats by direct injection into a lateral cerebral ventricle. Brain TrkA expression was increased significantly in hippocampus and entorhinal cortex (up to 32% above control), with no changes found in cerebral cortex or hypothalamus. The nicotine-induced increases in TrKA expression in hippocampus and entorhinal cortex were significantly inhibited by 10 μg α-BTX or by 10 nmol Aβ1–42. Therefore, physiologically relevant concentrations of Aβ1–42 can prevent nicotine-induced TrkA receptor expression in brain regions containing cholinergic neurons susceptible to the neurotoxicity associated with Alzheimer’s disease.     

胃粘膜上皮“适应性细胞保护”机制防止胃肿瘤发生的作用

投用致癌剂的对照组其胃肿瘤发生率为22.2％。若同时给予40％Z醇液空腹灌胃,则胃肿瘤发生率达55.9％。如在给乙醇液前15分钟,先给予4％的辣椒煎液灌胃,则胃肿瘤发生率只有20.0％,相近于对照组的水平(后2组差别有极显著意义,P<0.01)。这种给损伤剂(乙醇)之前先给予微刺激剂(辣椒)所产生的胃粘膜的保护作用,是通过促使胃粘膜上皮细胞合成内源性前列腺素(PGs)来实现的,是一种“适应性细胞保护”机制。这种保护胃粘膜的作用可降低胃肿瘤的发生率。     

Hepatoprotective action of prostaglandin A2 analogs under CCl4-induced liver injury in vitro

Aim: The cytoprotective effects of six novel synthetic prostaglandin A(2) analogs against carbon tetrachloride (CCl(4)) as a toxic agent were studied with isolated rat liver hepatocytes in vitro. Results: It was found that hepatocytes treatment with CCl(4) induced: (i) a significant increase of lactic dehydrogenase (LDH) release from cytoplasm; (ii) leakage of glutamate dehydrogenase (GDH) and acid phosphatase from mitochondria and lysosomes, respectively; (iii) 10-fold increase of trien conjugates formation; and (iv) a reduction of free SH-groups by 50%. Prostanoids U-26, U-9 and U-34 decreased cytotoxic index of CCl(4) on average by 1.5-2.0 times and were more effective than PGI(2), the well-known hepatoprotector of prostanoids type. The protective action of the prostanoids was not a cAMP- or Ca(2+)-dependent process. However, prostanoids U-26, U-9 and U-34 normalized intracellular content of SH-groups, reduced trien conjugates formation by 60-80% and strongly prevented enzyme leakage through cellular membranes. They were also able to inhibit CCl(4) effects via decreasing cytochrome P(450)2E1 activity. Conclusion: The results obtained demonstrate that prostanoids provide cytoprotective effects on liver hepatocytes through the prevention of lipid peroxidation of the plasma and the cellular membranes and maintenance of their barrier function.     

Gastric mucosal protection with β-phenylethylamine (PEA) and other sympathomimetic amines against absolute ethanol in the rat

The purpose of this study was to investigate the potential of -phenylethylamine (PEA), an amphetamine-like compound present in the blood during high stress situations, to protect rat gastric mucosa against absolute ethanol. F-344 rats were pretreated with PEA in saline at several dose levels and at various times prior to oral administration of 1 ml absolute ethanol. PEA at dose levels of 50 and 100 mg/kg significantly reduced the severity of alcohol-induced lesions following oral, but not parenteral, treatment. The duration of protection with PEA was approximately 90 min, with maximum protection observed when PEA was administered 15–30 min before alcohol. Pretreatment with indomethacin did not prevent or reduce the protection induced by PEA. Other sympathomimetic amines such as isoproterenol and ephedrin were similarly cytoprotective against absolute ethanol while amphetamine, phenylephrine, and epinephrine proved ineffective. These results add further support to the role of the sympathetic nervous system in regulating gastric mucosal protection in the rat.     

H_2O_2预处理对PC12细胞氧化应激损伤的适应性细胞保护作用

目的　探讨H2 O2 预处理对PC12细胞氧化应激损伤的适应性细胞保护作用及与脑源性神经营养因子 (brain de rivedneurotrophicfactor,BDNF)的关系。 方法　采用MTT法检测细胞活力 ,PI染色流式细胞术检测细胞凋亡 ,间接免疫荧光流式细胞术检测细胞BDNF的表达。结果　PC12细胞经 10 μmol·L-1H2 O2 预处理 90min后 ,2 0～ 6 0 μmol·L-1H2 O2 对PC12细胞生长的抑制程度明显下降 ,H2 O2 (2 0、30μmol·L-1)对PC12细胞凋亡的诱导作用明显受到抑制 ,BD NF的表达强度增强。结论　H2 O2 预处理对PC12细胞氧化应激损伤具有保护作用 ,其作用机制可能与增加脑源性神经营养因子表达有关     

A ROLE OF EGF IN GASTRIC MUCOSAL CYTOPROTECTION OF MOXIBUSTION

Ourperviousworkprovedthatmoxibustioncouldacceleratethehealingofexperimentalgas-triculcer,indicatingthatmoxibustionhadeffectOfgastricmucosalcytoprotection.[l]Itsmecha-nismisbeinginvestigatednow.Inourexperi-ments,wenoticedthatduringmoxibustiontherats'salivarysecretionincreasedanditwasswal-lowedalots.ConsideringthatsalivacontainsplentifulEGFandEGFplaysaroleinmaintain-ingtheintegrityofthegastricmucosaandinac-celeratingthehealingofgastriculcer,weholdthatitisnecessarytoinvestigatetheroleofEGFing…     

Caspase抑制剂的若干药理学研究进展

细胞凋亡 (apoptosis)失衡与许多疾病密切相关 ,而半胱天冬氨酸蛋白酶 (caspase)是执行细胞凋亡的蛋白酶家族 ,在凋亡过程中发挥关键作用 ,它可通过多种途径发生级联激活。一些天然和合成的caspase抑制剂能够抑制caspase家族中的一种或几种成员而发挥抗凋亡作用 ,有望成为治疗细胞过度凋亡而引起的相关疾病的有效手段。     

Amifostine: chemotherapeutic and radiotherapeutic protective effects

Amifostine (Ethyol?, Alza Pharmaceuticals) is an inorganic thiophosphate cytoprotective agent known chemically as ethanethiol, 2-[3- aminopropyl)amino]dihydrogen phosphate. It is a prodrug of free thiol (WR-1065) that may act as a scavenger of free radicals generated in tissues exposed to cytotoxic drugs and binds to reactive metabolites of such drugs. Amifostine was originally developed as a radioprotective agent in a classified nuclear warfare project. Following declassification of the project it was evaluated as a cytoprotective agent against toxicity of the alkylating drugs and cisplatin. Differences in the alkaline phosphatase concentration of normal versus tumour tissues can result in greater conversion of amifostine in normal tissues. Inside the cell, WR-1065 provides an alternative target to DNA and RNA for the reactive molecules of alkylating or platinum agents and acts as a potent scavenger of the oxygen free radicals induced by ionizing radiation and some chemotherapy agents. Preclinical animal studies have demonstrated that the administration of amifostine protects against a variety of chemotherapy-related toxicities including cisplatin-induced nephrotoxicity, cisplatin-induced neurotoxicity, cyclophosphamide- and bleomycin-induced pulmonary toxicity and the cytotoxicities (including cardiotoxicity) induced by doxorubicin and related chemotherapeutic agents. Amifostine has been shown to protect a variety of animal species from lethal doses of radiation. Amifostine gives haematological protection from cyclophosphamide, carboplatin, mitomycin C, fotemustine and radiotherapy; renal and peripheral nerve protection from cisplatin; mucosa, skin and salivary gland protection from radiotherapy. Multiple Phase I studies were carried out with amifostine in combination with chemotherapy for various neoplasms. Appropriate doses of amifostine were found to be 740 - 910 mg/m² in single-dose regimens and 340 mg/m² in multiple-dose regimens. In radioprotection, doses are generally 200 - 350 mg/m². For all these characteristics, amifostine has been recently approved and suggested in ASCO clinical practice guidelines as a radioprotector for head and neck cancer treatment and supportive agent during cisplatin-based chemotherapy, in lymphomas and solid tumours. Moreover, its spectrum of possible applications is enlarging. As data have been provided indicating that amifostine stimulates haematopoiesis, it has been employed with intriguing results in the treatment of myelodysplastic syndromes (MDS).     

Adverse effects of vagotomy on ethanol-induced gastric injury in the rat

Truncal vagotomy is known to aggravate the damaging effects of alcohol-induced gastric injury and prevent the occurrence of adaptive cytoprotection against such injury by a mild irritant. This study was undertaken to determine whether aberrations in glutathione (GSH) metabolism were responsible for these vagotomy-induced effects. Fasted rats (6–8/group) were subjected to truncal vagotomy and pyloroplasty or sham vagotomy and pyloroplasty. One week later they were given 2 ml of oral saline or the mild irritant, 25% ethanol (EtOH). Thirty minutes following such treatment, animals were either sacrificed or orally received 2 ml of 100% EtOH and then were sacrificed 5 min later. At sacrifice, in each experimental group, stomachs were removed and either evaluated macroscopically for the degree of injury involving the glandular gastric epithelium or samples of the mucosa were prepared for measurement of total GSH levels or GSH peroxidase (GPX) and GSH reductase (GRT) activity. In nonvagotomized animals, saline treatment prior to 100% EtOH exposure resulted in injury to the glandular epithelium involving approximately 18%. Treatment with 25% EtOH prior to 100% EtOH exposure virtually abolished this injury. In vagotomized animals, 100% EtOH elicited almost three times the amount of injury observed in the nonvagotomized state and the protective effect of 25% EtOH pretreatment was prevented. Effects of the various treatment modalities on GPX and GRT activity were not significantly different from control values. When mucosal GSH results were plotted against the presence or absence of gastric injury among the various groups studied, no significant correlation was apparent. Thus, aberrations in glutathione metabolism do not explain the absence of adaptive cytoprotection following vagotomy or the exacerbation of alcohol-induced damage under conditions of vagal denervation.This work was supported by research grant DK 25838 from the National Institutes of Health.