Biomedical subjects

B R Shivakumar

Publications and source records attributed to B R Shivakumar.

8 recordsLinked to original sources

PubMed1996

alpha-Lipoic acid protects against reperfusion injury following cerebral ischemia in rats.

Ischemic-reperfusion injury in humans occurs in conditions such as stroke, cardiac arrest, subarachnoid hemorrhage or head trauma. Maximal tissue damage is observed during reperfusion, which is primarily attributed to oxidative injury resulting from production of oxygen free radicals. One of the major consequences of such damage is the depletion of the cellular antioxidant, glutathione (GSH) leading to oxidation of protein thiols to disulfides and the loss of activity of critical enzymes having active thiol group(s). Thus, the maintenance of thiol homeostasis is an important factor in cell survival. The effect of thiol antioxidants like alpha-lipoic acid and the isopropyl ester of GSH was examined on the morbidity and mortality of rats subjected to reperfusion following cerebral ischemia induced by bilateral carotid artery occlusion and hypotension. While the GSH isopropyl ester had no significant protective effect; after pretreatment of rats, alpha-lipoic acid was detected in the rat brain and it dramatically reduced the mortality rate from 78% to 26% during 24 h of reperfusion. The natural thiol antioxidant, alpha-lipoic acid is effective in improving survival and protecting the rat brain against reperfusion injury following cerebral ischemia.

Animals↗

PubMed1995

Glutathione and protein thiol homeostasis in brain during reperfusion after cerebral ischemia.

The status of glutathione (GSH) and protein thiol homeostasis was examined in rat brain regions during reperfusion after moderate and severe cerebral ischemia. GSH levels were decreased in brain regions during reperfusion for 1 hr after moderate or severe ischemia for 0.5 hr. Maximal loss of GSH (50-66%) was observed in the striatum and hippocampus. The GSH lost from the brain regions was essentially recovered as protein-glutathione mixed disulfide (PrSSG) with concomitant loss of protein thiols (PrSH). The activities of enzymes such as Na+K+ ATPase, NADH dehydrogenase and glutathione reductase were also inhibited but were restored after incubation of the brain homogenate with dithiothreitol. The depletion of GSH was also accompanied by an increase in the levels of malondialdehyde and reactive oxygen species. The total GSH recovered as sum of GSH and PrSSG was significantly higher than the sham-operated controls in the hippocampus and striatum after 1 hr of reperfusion, after moderate ischemia for 0.5 hr, and at the end of 24 hr of reperfusion the GSH-protein thiol homeostasis was restored. In contrast after 1 hr of reperfusion after severe ischemia, the GSH recovered as sum of GSH and PrSSG was not significantly different from sham-operated controls and at the end of 24 hr, 7 of 9 animals died. The recuperation of the brain from oxidative stress during reperfusion after moderate ischemia was thus preceded by increased recovery of total GSH essentially in the form of PrSSG. Thus, rapid restoration of thiol homeostasis in the brain during reperfusion may help the brain recover from reperfusion injury.

Animals↗

PubMed1993

Oxidative stress and thiol modification induced by chronic administration of haloperidol.

Haloperidol, a widely used neuroleptic, acts through blockade of dopamine receptors leading to increased turnover of dopamine. Increased turnover of dopamine could lead to excessive production of hydrogen peroxide and, thus, generate oxidative stress. The effect of chronic administration of haloperidol on glutathione (GSH)-protein thiol homeostasis and lipid peroxidation was examined in rat brain regions. The oxidized GSH levels increased significantly, though not substantially, in cortex (CT, 15%), striatum (ST, 28%) and midbrain (MB, 27%). Maximal decreases in GSH levels were noted in CT (23%), ST (28%) and MB (20%) after 1 month of haloperidol administration. The GSH levels recovered thereafter, and after 6 months of haloperidol treatment, the GSH levels were not significantly different from control in ST and MB. The depleted GSH was recovered essentially as protein-GSH mixed disulfide with a concomitant decrease in the protein thiol concentration in all the three regions of the brain. The increase in oxidized GSH concentration represented only 1.8, 2.0 and 3.5% of the depleted GSH in the CT, ST and MB after 1 month of haloperidol administration. The concentration of thiobarbituric acid-reactive products increased significantly up to 3 months of haloperidol treatment, but at the end of 6 months, the levels were substantially decreased. The present study demonstrates that haloperidol administration for 1 month results in significant oxidative stress in CT, ST and MB regions of the brain, as demonstrated by alterations in GSH-protein thiol homeostasis and increased lipid peroxidation products. However, after prolonged administration of haloperidol for 6 months, the GSH-protein thiol homeostasis is restored to a large extent, concomitant with the decrease in the concentration of lipid peroxidation products. Administration of haloperidol leads to development of tolerance (supersensitivity of the dopamine autoreceptors) to neuroleptics, which is associated with decreased turnover of dopamine; this may result in overcoming the oxidative stress generated initially due to increased dopamine turnover.

Animals↗

PubMed1992

Oxidative stress induced by administration of the neuroleptic drug haloperidol is attenuated by higher doses of haloperidol.

The effect of haloperidol administration on lipid peroxidation and glutathione/protein thiol homeostasis in the brain was examined 4 h following subcutaneous administration of a single dose of haloperidol; 1.0, 1.5, 2.0 or 2.5 mg/kg b.wt. Glutathione (GSH) levels decreased significantly in cortex, striatum and midbrain after haloperidol administration. Maximal decrease of GSH was observed in the striatum. The depleted GSH was recoverable as protein glutathione mixed disulfide (Pr-SSG) with concomitant loss of protein thiols (Pr-SH) in all the regions of the brain examined. Administration of 1.5 mg/kg b.wt. of haloperidol resulted in significant depletion of GSH in striatum and midbrain as compared to that after administration of the lower dose of 1.0 mg/kg b.wt. of haloperidol. However, administration of higher doses of haloperidol (2.0 and 2.5 mg/kg b.wt.) did not result in greater depletion of GSH; the GSH levels were not significantly different from that observed following the administration of 1.5 mg/kg b.wt. of haloperidol. However, Pr-SSG levels increased dose-dependently following haloperidol administration. The total GSH recovered as sum of GSH and Pr-SSG was significantly higher than controls in striatum and midbrain following administration of higher doses of haloperidol, namely, 2.0 and 2.5 mg/kg b.wt. The depleted GSH was not recoverable as glutathione disulfide (GSSG). GSSG levels were not significantly different from controls 4 h after administration of 1.5 mg/kg b.wt. of haloperidol. The levels of malondialdehyde (indicative of lipid peroxidation) increased significantly as compared to control levels (280-220%) following administration of 1.0 and 1.5 mg/kg b.wt. of haloperidol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Selective modulation of glutathione in mouse brain regions and its effect on acrylamide-induced neurotoxicity.

Selective modulation of brain glutathione (GSH) may assist the elucidation of the role of GSH in the central nervous system. Subcutaneous administration of diethyl maleate (DEM) depleted both cerebral and hepatic GSH in a dose- and time-dependent manner. While hepatic GSH levels returned to control levels 6 hr after DEM administration, brain GSH levels remained significantly lowered for up to 12 hr after administration of DEM. However, intrathecal administration of DEM resulted in a selective lowering of brain GSH without altering hepatic levels. Intrathecal administration of L-buthionine sulfoximine (L-BSO; 1.0 mmol/kg body wt) also depleted the GSH content of the brain and the levels remained low 24 hr after L-BSO administration. The extent of GSH depletion varied in different regions of the brain; maximal depletion was observed in the brainstem, followed by the cerebellum, striatum, cortex and hippocampus. Intrathecal administration of L-2-oxothiazolidine 4-carboxylate (OTC) resulted in a marginal elevation of GSH levels in the brain. There was considerable regional variation. A maximal elevation of 134% was seen in the hippocampus, 6 hr following the intrathecal administration of 8.0 mmol of OTC/kg body wt. The effect of the modulation of brain GSH levels on acrylamide (ACR)-induced neurotoxicity was examined. Depletion of GSH by pretreatment of mice with L-BSO or DEM (administered intrathecally) enhanced the toxicity of ACR as measured by the inhibition of brain glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity. The inhibition of GAPDH by ACR was attenuated by pretreatment of animals with OTC. Thus, brain GSH may play an important role in the detoxification of xenobiotics, in situ within the central nervous system.

Acrylamides↗

PubMed1992

Glutathione homeostasis in brain during reperfusion following bilateral carotid artery occlusion in the rat.

Rats were subjected to bilateral carotid artery occlusion for 30 min, followed by reperfusion for varying time periods. The concentration of reduced and oxidized glutathione, glutathione peroxidase and glutathione reductase were determined in whole brain after varying periods of reperfusion. Lipid peroxidation was also assessed by determining the levels of malondialdehyde (MDA) in the brain. Reperfusion for 1 hr following bilateral carotid artery occlusion resulted in significant decrease in total glutathione (GSH) concentration along with small but significant increase in oxidized glutathione (GSSG) levels. After 4 hr of reperfusion, GSH levels recovered, although GSSG levels remained elevated up to 12 hr of reperfusion. Increase in malondialdehyde levels was also detected in the brain up to 12 hr of reperfusion. Glutathione reductase activity remained significantly low up to 144 hr of reperfusion, while glutathione peroxidase activity remained unaffected. These results demonstrate that oxidative stress is generated in the brain during reperfusion following partial ischemia due to bilateral carotid artery occlusion.

Animals↗

PubMed1991

Free radical scavenging systems in developing rat brain.

Because the developing brain is subject to high oxygen tension and lacks a functional bloodbrain anti-oxidant protection is important to development in the brain. The levels of superoxide dismutase, copper-zinc superoxide dismutase, manganese superoxide dismutase, catalase, glutathione and related enzymes, namely, glutathione reductase and glutathione peroxidase were determined in rat brain at various stages of development. The levels of thiobarbituric acid reactive products, indicative of lipid peroxidation, were very low at birth and increased to adult levels by the 16th day after birth. Brain glutathione levels displayed significant variations during the first 2 weeks after birth but not thereafter. Catalase activity in developing brain slowly increased over 45 days. Total superoxide dismutase activity in 1-day-old rat brain, 80% of the adult rat brain level, subsequently decreased on day 6. Total superoxide dismutase activity, however, increased again in 10-day-old rats and remained constant thereafter. While the developmental pattern of manganese superoxide dismutase was similar to that of the total superoxide dismutase, the copper-zinc superoxide dismutase levels were low at birth and reached adult levels on the 10th day after birth. There was no variation in glutathione reductase and peroxidase levels except for a decrease on day 16 of glutathione reductase and slow increase in adult levels by day 28. The present findings suggest that the overall levels of antioxidant enzymes in the developing brain are comparable to a large extent to those present in the adult brain. In contrast to the developing brain, hepatic levels of glutathione, total superoxide dismutase, manganese superoxide dismutase are significantly lower at birth and increase during development.

Animals↗

PubMed1989

Low glutathione levels in brain regions of aged rats.

Glutathione (GSH) was measured in 6 regions of brain and liver of young adult, middle-aged and aged rats. GSH levels were significantly lower in cortex, cerebellum, striatum, thalamus and hippocampus of aged rats, while no changes were observed in liver as compared to young adult rats. On the other hand, lipid peroxidation as measured by thiobarbituric acid-reactive products increased significantly in all the regions of brain examined and in the liver of aged rats. Since GSH plays an important role as a cellular protectant against oxygen radical-mediated injury, decreased levels of GSH in aged rat brain are indicative of the vulnerability of the aged cerebral tissue to oxidative injury.

Aging↗