Chemical constituents from Euphorbia hirta

Thirty-one compounds, including fourteen triterpenoids (1–14), seven coumarins (15–21), four lignans (22–25), and six diterpenes (26–31) were isolated from the aerial part of Euphorbia hirta. The structures were elucidated by spectroscopic methods and by comparison of their reported spectroscopic data. These compounds have shown the chemical relationships between this plant and other species from the genus Euphorbia.     

Cimetidine protects against acetaminophen toxicity

Generally, acetaminophen (APAP) overdoses with elimination half-lives over 4 hr. sustain liver damage. In the following cases, cimetidine (C) seems to have protected against APAP toxicity. An 18 yr. old, 64 kg female smoker presented 6 hr. after taking 10_Rg APAP, 1200+ mg C, and small amounts of flurazepam and Sleepeze (methaprilene + scopolamine). Three plasma APAP levels (by HPLC) revealed an elimination half-life of 4.4 hr. C did not interfere with the APAP assay. Despite the long half-life in a patient with microsomal enzymes induced by smoking, no evidence of hepatotoxicity developed. A month later, the same patient overdosed with APAP alone. Three plasma levels revealed a 3.3 hr. half-life. Lack of toxicity in the presence of a long elimination half-life may indicate a protective action of C in APAP overdoses.     

Carvedilol protects against the renal mitochondrial toxicity induced by cisplatin in rats

The clinical use of cisplatin is highly limited by its nephrotoxicity, which has been associated with mitochondrial dysfunction. We investigated the protective effect of carvedilol, an antihypertensive with strong antioxidant properties, against the nephrotoxicity induced by cisplatin in rats. Carvedilol was able to counteract the renal damage by preventing the mitochondrial dysfunction induced by cisplatin. The mitochondrial eletrochemical potential, calcium uptake, respiration and the phosphorylative capacity were preserved by the co-administration of carvedilol. The mechanism of protection probably does not involve alterations in the cellular and sub-cellular distribution of cisplatin. The study suggests that carvedilol is a potential drug for the adjuvant nephroprotective therapy during cisplatin chemotherapy.     

Glutathione protects cells against arsenite-induced toxicity

To understand the role of glutathione (GSH) in the protection of cells from arsenite toxicity, we studied the mechanism of apoptotic cell death in cells genetically unable to synthesize GSH (GCS-2 cells). Arsenite stimulated an increase in protein ubiquitination in GCS-2 cells while the wild-type cells were unaffected. Arsenite treatment increased lipid peroxidation and induced ubiquitination of molecular chaperone Hsp90 and impaired its ability to bind cochaperone p50(Cdc-37) and client proteins Plk-1 and Cdk-4 in GCS-2 cells. Treatment with arsenite also partially inhibited proteasome activity in GCS-2 cells. In these cells stably transfected with GFP(u) (a reporter consisting of a short degron fused to the COOH-terminus of GFP), intracellular fluorescence increased, suggesting the accumulation of GFP aggregates. GCS-2 cells underwent apoptosis accompanied by release of cytochrome c into the cytoplasm. Taken together, these data suggest that a possible mechanism of arsenite-induced apoptosis is the accumulation of ubiquitinated proteins and impairment of the protein degradative pathway. Further, protection from arsenite-induced ubiquitination is mediated by GSH and to a lesser extent by available reducing equivalents in the cells.     

Levetiracetam protects against kainic acid-induced toxicity

We investigated the Levetiracetam (LVT) ability to protect the brain against kainic acid (KA) induced neurotoxicity. Brain injury was induced by intraperitoneal administration of KA (10 mg/kg). Sham brain injury rats were used as controls. Animals were randomized to receive either LVT (50 mg/kg) or its vehicle (1 ml/kg) 30 min. before KA administration. Animals were sacrificed 6 hours after KA injection to measure brain malonildialdehyde (MDA), glutathione levels (GSH) and the mRNA for interleukin-1beta (IL-1beta) in the cortex and in the diencephalon. Behavioral changes were also monitored. Intraperitoneal administration of LVT decreased significantly MDA in the cortex (KA + vehicle = 0.25 +/- 0.03 nmol/mg protein; KA + LVT = 0.13 +/- 0.01 nmol/mg protein; P < 0.005), and in the diencephalons (KA + vehicle = 1,01 +/- 0.2 nmol/mg protein; KA + LVT = 0,33 +/- 0,08 nmol/mg protein; P < 0.005), prevented the brain loss of GSH in both cortex (KA + vehicle = 5 +/- 1 micromol/g protein; KA + LVT = 15 +/- 2 micromol/g protein; P < 0.005) and diencephalons (KA + vehicle = 9 +/- 0.8 micromol/g protein; KA + LVT = 13 +/- 0.3 micromol/g protein; P < 0.05), reduced brain IL-1beta mRNA and markedly controlled seizures. Histological analysis showed a reduction of cell damage in LVT treated samples. The present data indicate that LVT displays neuro-protective effects against KA induced brain toxicity and suggest that these effects are mediated, at least in part, by inhibition of lipid peroxidation.     

Interleukin 1 protects rats against oxygen toxicity

We studied the effect of interleukin 1 alpha (IL-1) in the protection against O2 toxicity. Tracheal insufflation of IL-1 resulted in a dose-dependent protection against O2 toxicity. All control rats died within 3 days of O2 exposure. In contrast, 84, 71, and 20% of rats insufflated with 5, 1, and 0.2 microgram(s) IL-1 (150, 30, and 6 x 10(4) U), respectively, survived 100% O2 exposure for greater than 11 days. At 2.3 days after O2 exposure, control rats showed severe pulmonary injury, which insufflation of 5 microgram(s) IL-1 markedly attenuated. The protection against O2 toxicity was associated with a selective enhancement of pulmonary Mn-superoxide dismutase (Mn-SOD) activity in IL-1-insufflated rats. In rats insufflated with IL-1 that survived exposure to 100% O2 for 7 days, the activities of pulmonary Mn-SOD, Cu,Zn-SOD, catalase, and glutathione peroxidase were all increased. The increased pulmonary Mn-SOD activity demonstrated in IL-1-insufflated rats at 2.3 days after O2 exposure may contribute to the protection against acute O2 toxicity, and the markedly increased activities of all pulmonary antioxidant enzymes shown in rats insufflated with IL-1 that survived O2 exposure for 7 days may in part be responsible for the chronic adaptation of these rats to a 100% O2 environment.     

Kaempferol protects against rat striatal degeneration induced by 3-nitropropionic acid

3-Nitropropionic acid (NPA) produces degeneration of striatum and some neurological disturbances characteristic of Huntington's disease in rodents and primates. We have shown that the flavonoid kaempferol largely reduced striatal damage induced by cerebral ischaemia-reperfusion in rats ( Lopez-Sanchez et al. 2007 ). In this work, we report that intraperitoneal (i.p.) administration of kaempferol affords an efficient protection against NPA-induced neurodegeneration in Wistar rats. We studied the effects of daily i.p. injections of 7, 14 and 21 mg of kaempferol/kg body weight during the NPA-treatment (25 mg/kg body weight/12 h i.p., for 5 days) on the neurological deficits, degeneration of rat striatum and oxidative stress markers. Intraperitoneal injections of 14–21 mg of kaempferol/kg body weight largely attenuated motor deficit and delayed mortality. The higher dose of kaempferol prevented the appearance of NPA-induced striatal lesions up to the end of treatment, as revealed by haematoxylin-eosin and TUNEL staining, and also NPA-induced oxidative stress, because it blocked the fall of reduced glutathione and the increase of protein nitrotyrosines in NPA-treated rats. It was found that striatal degeneration was associated with calpains activation and a large inactivation of creatine kinase, which were also prevented when the higher doses of kaempferol were administered.     

Melanin protects choroidal blood vessels against light toxicity

Low ocular pigmentation and high long-term exposure to bright light are believed to increase the risk of developing age-related macular degeneration (ARMD). To investigate the role of pigmentation during bright light exposure, cell damage in retinae and choroids of pigmented and non-pigmented rats were compared. Pigmented Long Evans (LE) rats and non-pigmented (albino) Wistar rats were exposed to high intensity visible light from a cold light source with 140,000 lux for 30 min. Control animals of both strains were not irradiated. The animals had their pupils dilated to prevent light absorbance by iris pigmentation. 22 h after irradiation, the rats were sacrificed and their eyes enucleated. Posterior segments, containing retina and choroid, were prepared for light and electron microscopy. Twenty different sections of specified and equal areas were examined in every eye. In albino rats severe retinal damage was observed after light exposure, rod outer segments (ROS) were shortened and the thickness of the outer nuclear layer (ONL) was significantly diminished. Choriocapillaris blood vessels were obstructed. In wide areas the retinal pigment epithelium (RPE) was absent in albino rats after irradiation. In contrast, LE rats presented much less cell damage in the RPE and retina after bright light exposure, although intra-individual differences were observed. The thickness of the ONL was almost unchanged compared to controls. ROS were shortened in LE rats, but the effect was considerably less than that seen in the albinos. Only minimal changes were found in choroidal blood vessels of pigmented rats. The RPE showed certain toxic damage, but cells were not destroyed as in the non-pigmented animals. The number of melanin granules in the RPE of LE rats was reduced after irradiation. Ocular melanin protects the retina and choroid of pigmented eyes against light-induced cell toxicity. Physical protection of iris melanin, as possible in eyes with non-dilated pupils, does not seem to play a major role in our setup. Biochemical mechanisms, like reducing oxidative intracellular stress, are more likely to be responsible for melanin-related light protection in eyes with dilated lens aperture.     

Autophagy protects renal tubular cells against cyclosporine toxicity

A major side effect of the powerful immunosuppressive drug cyclosporine (CsA) is the development of a chronic nephrotoxicity whose mechanisms are not fully understood. Recent data suggest that tubular cells play a central role in the pathogenesis of chronic nephropathies. We have shown that CsA is responsible for endoplasmic reticulum (ER) stress in tubular cells. Autophagy has recently been described to be induced by ER stress and to alleviate its deleterious effects. In this study, we demonstrate that CsA induces autophagy in primary cultured human renal tubular cells through LC3II expression and autophagosomes visualization by electron microscopy. Autophagy is dependant of ER stress because various ER stress inducers activate autophagy and salubrinal, an inhibitor of eIF2α dephosphorylation that protects cells against ER stress, inhibited LC3II expression. Furthermore, autophagy inhibition during CsA treatment with beclin1 siRNA significantly increases tubular cell death. Finally, immunohistochemical analysis of rat kidneys demonstrates a positive LC3 staining on injured tubular cells, suggesting that CsA induces autophagy in vivo. Taken together, these results demonstrate that CsA, through ER stress induction, activates autophagy as a protection against cell death.     

Autophagy protects renal tubular cells against cyclosporine toxicity

A major side effect of the powerful immunosuppressive drug cyclosporine (CsA) is the development of a chronic nephrotoxicity whose mechanisms are not fully understood. Recent data suggest that tubular cells play a central role in the pathogenesis of chronic nephropathies. We have shown that CsA is responsible for endoplasmic reticulum (ER) stress in tubular cells. Autophagy has recently been described to be induced by ER stress and to alleviate its deleterious effects. In this study, we demonstrate that CsA induces autophagy in primary cultured human renal tubular cells through LC3II expression and autophagosomes visualization by electron microscopy. Autophagy is dependant on ER stress because various ER stress inducers activate autophagy, and salubrinal, an inhibitor of eIF2alpha dephosphorylation that protects cells against ER stress, inhibited LC3II expression. Furthermore, autophagy inhibition during CsA treatment with beclin1 siRNA significantly increases tubular cell death. Finally, immunohistochemical analysis of rat kidneys demonstrates a positive LC3 staining on injured tubular cells, suggesting that CsA induces autophagy in vivo. Taken together, these results demonstrate that CsA, through ER stress induction, activates autophagy as a protection against cell death.     

Pramipexole protects against MPTP toxicity in non-human primates

The neurotoxin MPTP induces nigral dopaminergic cell death in primates and produces a partial model of Parkinson's disease (PD). Pramipexole is a D2/D3 dopamine receptor agonist used in the symptomatic treatment of PD, and which also protects neuronal cells against dopaminergic toxins in vitro. We now demonstrate that pramipexole partially prevents MPTP toxicity in vivo in a primate species. Common marmosets were repeatedly treated with pramipexole either before, coincidentally with, or after low-dose MPTP treatment designed to induce a partial lesion of the substantia nigra. Animals pretreated with pramipexole had a significantly greater number of surviving tyrosine hydroxylase (TH) positive neurones in the pars compacta of the substantia nigra. Pramipexole pretreatment also prevented degeneration of striatal dopamine terminals. Treatment with pramipexole concurrently with MPTP or following MPTP did not prevent TH-positive cell loss. Pramipexole pretreatment appears to induce adaptive changes that protect against dopaminergic cell loss in primates.     

Metal swap between Zn7-metallothionein-3 and amyloid-beta-Cu protects against amyloid-beta toxicity

Aberrant interactions of copper and zinc ions with the amyloid-beta peptide (Abeta) potentiate Alzheimer's disease (AD) by participating in the aggregation process of Abeta and in the generation of reactive oxygen species (ROS). The ROS production and the neurotoxicity of Abeta are associated with copper binding. Metallothionein-3 (Zn(7)MT-3), an intra- and extracellularly occurring metalloprotein, is highly expressed in the brain and downregulated in AD. This protein protects, by an unknown mechanism, cultured neurons from the toxicity of Abeta. Here, we show that a metal swap between Zn(7)MT-3 and soluble and aggregated Abeta(1-40)-Cu(II) abolishes the ROS production and the related cellular toxicity. In this process, copper is reduced by the protein thiolates forming Cu(I)(4)Zn(4)MT-3, in which an air-stable Cu(I)(4)-thiolate cluster and two disulfide bonds are present. The discovered protective effect of Zn(7)MT-3 from the copper-mediated Abeta(1-40) toxicity may lead to new therapeutic strategies for treating AD.     

Schisandrin B protects against tert-butylhydroperoxide induced cerebral toxicity by enhancing glutathione antioxidant status in mouse brain

Schisandrin B (Sch B), a dibenzocyclooctadiene derivative isolated from Fructus Schisandrae, has been shown to produce antioxidant effect on rodent liver and heart. A mouse model of tert-butylhydroperoxide (t-BHP) induced cerebral toxicity was adopted for examining the antioxidant potential of Sch B in the brain. Intracerebroventricular injection of t-BHP caused a time-dependent increase in mortality rate in mice. The t-BHP toxicity was associated with an increase in the extent of cerebral lipid peroxidation and an impairment in cerebral glutathione antioxidant status, as evidenced by the abrupt decrease in reduced glutathione (GSH) level and the inhibition of Se-glutathione peroxidase activity at 5 min following t-BHP challenge. Sch B pretreatment (1 or 2 mmol/kg/day × 3) produced a dose-dependent protection against t-BHP induced mortality. The protection was associated with a decrease in the extent of lipid peroxidation and an enhancement in glutathione antioxidant status in brain tissue detectable at 5 min post t-BHP challenge, with the assessed biochemical parameters being returned to normal values at 60 min in Sch B pretreated mice at a dose of 2 mmol/kg. The ensemble of results suggests the antioxidant potential of Sch B pretreatment in protecting against cerebral oxidative stress.     

Lycopene protects against cyclosporine A-induced testicular toxicity in rats

Cyclosporine A (CsA)-induced direct failures in hypothalamic-pituitary-gonadal axis and Sertoli cell phagocytic function have been considered for testicular toxicity so far. It has clearly been reported that oxidative stress leads to damage in sperm functions and structure of the testis. Therefore, this study was conducted to demonstrate whether CsA causes testicular and spermatozoal toxicity associated with the oxidative stress, and to investigate the possible protective effect of lycopene against CsA-induced damages in all reproductive organs and sperm characteristics in male rats. While the daily administration of CsA at the dose 15 mg/kg for 21 days significantly decreased the seminal vesicles weight, epididymal sperm concentration, motility, testicular tissue glutathione (GSH), glutathione peroxidase (GSH-Px) and catalase (CAT), diameter of seminiferous tubules and germinal cell thickness, it increased malondialdehyde (MDA) level and abnormal sperm rates along with degeneration, necrosis, desquamative germ cells in testicular tissue. However, the CsA along with simultaneous administration of lycopene at the dose of 10mg/kg markedly ameliorated the CsA-induced all the negative changes observed in the testicular tissue, sperm parameters and oxidant/antioxidant balance. In conclusion, CsA-induced oxidative stress leads to the structural and functional damages in the testicular tissue and sperm quality of rats and, lycopene has a potential protective effect on these damages.