Protective role of exogenous α-lipoic acid (ALA) on hippocampal antioxidant status and memory function in rat pups exposed to sodium arsenite during the early post-natal period

Effect of α-lipoic acid on spatial memory and structural integrity of developing hippocampal neurons in rats subjected to sodium arsenite exposure

BACKGROUND

Exposure to arsenic has been reported to affect the nervous system in a number of ways. Various epidemiological studies suggest cognitive impairment in subjects following exposure to environmental arsenic. The goal of the present study was to determine if supplementation of exogenous α-lipoic acid (ALA) could ameliorate sodium arsenite (NaAsO₂) induced adverse effects on learning and memory and synaptic connectivity in rat hippocampus.

METHODS

Accordingly, NaAsO₂ alone (1.5/2.0 mg/kg bw) or NaAsO₂ along with ALA (70 mg/kg bw) was administered by intraperitoneal (i.p.) route from postnatal day (PND) 4-17 to Wistar rat pups (experimental groups) and the Control groups received either distilled water or no treatment at all. After carrying out Elevated Plus Maze (EPM) and Morris Water Maze (MWM) test, the fresh brain tissues were collected on PND 18 and processed for Golgi Cox staining.

RESULTS

Observations of MWM test revealed impaired learning and memory in iAs alone treated animals as against those co-exposed to iAs and ALA. In Golgi stained hippocampal sections of iAs alone treated animals, decreased dendritic arborization and reduced number of spines in pyramidal neurons (CA1) and granule cells (DG) was observed whereas neuronal morphology was preserved in the controls and ALA supplemented groups CONCLUSIONS: These observations are suggestive of beneficial effects of ALA on iAs induced effects on learning and memory as well as on hippocampal neuronal morphology.

Ameliorative role of antioxidant supplementation on sodium-arsenite induced adverse effects on the developing rat cerebellum

Background

Arsenic is an environmental contaminant of global concern. Consumption of ground water contaminated with inorganic arsenic (iAs) continues to be the major source of its exposure. The developing nervous system is especially vulnerable to environmental insults due to its higher rate of oxygen consumption and provision of weaker antioxidant (AOX) machinery.

Objective

Since oxidative stress has been reported as one of the major factors underlying iAs induced toxicity, the aim of the present study is to study the effect of two AOXs i.e., Alpha Lipoic Acid (ALA) and Curcumin (Cur) in developing cerebellum of rats exposed to arsenic during postnatal period.

Materials and Methods

The study was carried out on mother reared neonatal rat pups grouped as normal (Ia) and sham (vehicle) controls (Ib,c,d), while the experimental groups IIa/ IIb received sodium arsenite (NaAsO2) [(1.5/2.5 mg/kg body weight (bw)] alone or along with ALA (70 mg/kg bw)- IIIa/ IIIb or along with Cur (150 mg/kg bw)- IVa/ IVb. Behavioural, biochemical and immunohistochemical procedures were carried out to understand the underlying mechanisms.

Results

The observations indicated deficits in locomotor function, accumulation of iAs, increased levels of oxidative stress markers along with downregulation of the expression of proteins closely associated with synaptic functioning (Synaptophysin and Postsynaptic density protein95) in the cerebellum of iAs treated animals. Substantial recovery in all these parameters was observed in AOX co-treated groups.

Conclusion

Our results support the potential of ALA and Cur in amelioration of iAs induced developmental neurotoxicity. ALA and Cur can be proposed as dietary adjuvants amongst populations inhabiting areas with high iAs contamination as a safe and cost effective antidotes.

Antioxidant supplementation upregulates calbindin expression in cerebellar Purkinje cells of rat pups subjected to post natal exposure to sodium arsenite

Optimal cytoplasmic calcium (Ca²⁺) levels have been associated with adequate cell functioning and neuronal survival. Altered intracellular Ca²⁺ levels following impaired Ca²⁺ homeostasis could induce neuronal degeneration or even cell death. There are reports of arsenite induced oxidative stress and the associated disturbances in intracellular calcium homeostasis. The present study focused on determining the strategies that would modulate tissue redox status and calcium binding protein (CaBP) (Calbindin D28k-CB) expression affected adversely by sodium arsenite (NaAsO₂) exposure (postnatal) of rat pups. NaAsO₂ alone or along with antioxidants (AOXs) (alpha lipoic acid or curcumin) was administered by intraperitoneal (i.p.) route from postnatal day (PND) 1-21 (covering rapid brain growth period - RBGP) to experimental groups and animals receiving sterile water by the same route served as the controls. At the end of the experimental period, the animals were subjected to euthanasia and the cerebellar tissue obtained therefrom was processed for immunohistochemical localization and western blot analysis of CB protein. CB was diffusely expressed in cell body as well as dendritic processes of Purkinje cells (PCs) along the PC Layer (PCL) in all cerebellar folia of the control and the experimental animals. The multilayered pattern of CB +ve cells along with their downregulated expression and low packing density was significantly evident in the arsenic (iAs) alone exposed group as against the controls and AOX supplemented groups. The observations are suggestive of AOX induced restoration of CaBP expression in rat cerebellum following early postnatal exposure to NaAsO₂.

α-lipoic acid inhibits oxidative stress in testis and attenuates testicular toxicity in rats exposed to carbimazole during embryonic period

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The intrauterine exposure of carbiamzole (CBZ) on male fertility is not well defined.

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CBZ exposure in utero results in spermatotoxic effects and impaired steroidogenesis in offspring rats at their adulthood.

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Gestational exposure to CBZ augmented testicular oxidative damage in offspring rats.

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α-lipoic acid supplementation with its antioxidant properties ameliorated diminished male reproductive health in rats exposed to CBZ prenatally.

The aim of this study was to evaluate the probable protective effect of α-lipoic acid against testicular toxicity in rats exposed to carbimazole during the embryonic period. Time-mated pregnant rats were exposed to carbimazole from the embryonic days 9–21. After completion of the gestation period, all the rats were allowed to deliver pups and weaned. At postnatal day 100, F1 male pups were assessed for the selected reproductive endpoints. Gestational exposure to carbimazole decreased the reproductive organ indices, testicular daily sperm count, epididymal sperm variables viz., sperm count, viable sperm, motile sperm and HOS-tail coiled sperms. Significant decrease in the activity levels of 3β- and 17β-hydroxysteroid dehydrogenases and expression of StAR mRNA levels with a significant increase in the total cholesterol levels were observed in the testis of experimental rats over the controls. These events were also accompanied by a significant reduction in the serum testosterone levels in CBZ exposed rats, indicating reduced steroidogenesis. In addition, the deterioration of the testicular architecture and reduced fertility ability were noticed in the carbimazole exposed rats. Significant reduction in the activity levels of superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase and reduced glutathione content with a significant increase in the levels of lipid peroxidation were observed in the testis of carbimazole exposed rats over the controls. Conversely, supplementation of α-lipoic acid (70 mg/Kg bodyweight) ameliorated the male reproductive health in rats exposed to carbimazole during the embryonic period as evidenced by enhanced reproductive organ weights, selected sperm variables, testicular steroidogenesis, and testicular enzymatic and non-enzymatic antioxidants. To conclude, diminished testicular antioxidant balance associated with reduced spermatogenesis and steroidogenesis might be responsible for the suppressed reproduction in rats exposed to the carbimazole transplacentally. On the other hand, α-lipoic acid through its antioxidant and steroidogenic properties mitigated testicular toxicity which eventually restored the male reproductive health of carbimazole-exposed rats.

Biological effects and epidemiological consequences of arsenic exposure, and reagents that can ameliorate arsenic damage in vivo

Through contaminated diet, water, and other forms of environmental exposure, arsenic affects human health. There are many U.S. and worldwide "hot spots" where the arsenic level in public water exceeds the maximum exposure limit. The biological effects of chronic arsenic exposure include generation of reactive oxygen species (ROS), leading to oxidative stress and DNA damage, epigenetic DNA modification, induction of genomic instability, and inflammation and immunomodulation, all of which can initiate carcinogenesis. High arsenic exposure is epidemiologically associated with skin, lung, bladder, liver, kidney and pancreatic cancer, and cardiovascular, neuronal, and other diseases. This review briefly summarizes the biological effects of arsenic exposure and epidemiological cancer studies worldwide, and provides an overview for emerging rodent-based studies of reagents that can ameliorate the effects of arsenic exposure in vivo. These reagents may be translated to human populations for disease prevention. We propose the importance of developing a biomarker-based precision prevention approach for the health issues associated with arsenic exposure that affects millions of people worldwide.

Alpha lipoic acid (ALA) modulates expression of apoptosis associated proteins in hippocampus of rats exposed during postnatal period to sodium arsenite (NaAsO2)

The present study focused on the role of exogenous alpha lipoic acid (ALA) in amelioration of inorganic arsenic (iAs) induced effects on apoptosis and apoptosis associated proteins in developing rat hippocampus. NaAsO2 (1.5/2.0 mg/kg bw) alone or along with ALA (70 mg/kg bw) was administered to rat pups (experimental groups) by intraperitoneal (i.p.) route from postnatal day (PND) 4-15. Controls received no treatment/distilled water/ALA. On PND 16, the animals were perfusion fixed and the brains were processed for paraffin embedding (CV and TUNEL staining) and cryopreservation (immunohistochemistry). The fresh brain tissue was used for Western blotting. Significant increase was observed in TUNEL positive cells and Bax (pro-apoptotic protein) expression in hippocampal sub-regions of iAs alone treated groups, whereas Bcl-2 expression was intensified in animals receiving ALA with iAs. Densitometric analysis (Western blots) revealed optimal restoration of Bax and Bcl-2 ratio in animals receiving ALA with iAs, thereby suggesting the protective role of ALA in iAs induced developmental neurotoxicity.

Postnatal Exposure to Sodium Arsenite (NaAsO(2)) Induces Long Lasting Effects in Rat Testes

Objective:

The present study was undertaken to investigate the effects of early postnatal exposure to sodium arsenite (NaAsO₂) on rat testis.

Materials and Methods:

Wistar rat pups were administered aqueous solution of NaAsO_2, 1.5 mg/kg body weight (bw) (experimental) and distilled water (control), respectively, by intraperitoneal route (i.p.) from postnatal day (PND) 1 to 14. Testes were collected after 1, 7 and 36 days (at PND 15, 21 and 50) after the treatment period (PND1-14) from the animals and immersion fixed in Bouin's fluid followed by paraffin embedding. Seven micrometer thick serial sections were cut and stained with hematoxylin and eosin for light microscopic observations. At PND 50, morphological features of sperms and their counting was carried out besides processing the perfusion-fixed testes for electron microscopy (EM).

Results and Conclusions:

The observations revealed an altered morphology of the seminiferous tubules (ST) along with degeneration and dissociation of spermatogenic cells in the experimental animals at PND 15, 21 and 50. Also, increased number of sperms with abnormal morphology and decreased sperm count was noted in the experimental animals. These features together with electron microscopic observations of abnormal mitochondria and apoptotic nuclei of spermatogonia and spermatocytes could be indicative of long-lasting adverse effects on the rat testis induced by exposure to As during early postnatal period.