Grandhi Venkata Ramalingayya

Naringin and Rutin Alleviates Episodic Memory Deficits in Two Differentially Challenged Object Recognition Tasks

Background: Cognitive decline or dementia is a debilitating problem of neurological disorders such as Alzheimers and Parkinsons disease, including special conditions like chemobrain. Dietary flavonoids proved to be efficacious in delaying the incidence of neurodegenerative diseases. Two such flavonoids, naringin (NAR) and rutin (RUT) were reported to have neuroprotective potential with beneficial effects on spatial and emotional memories in particular. However, the efficacy of these flavonoids is poorly understood on episodic memory, which comprises an important form of autobiographical memory.Objective: This study objective is to evaluate NAR and RUT to reverse time-delay-induced long-term and scopolamine-induced short-term episodic memory deficits in Wistar rats. Materials and Methods: We have evaluated both short-term and long-term episodic memory forms using novel object recognition task. Open field paradigm was used to assess locomotor activity for any confounding influence on memory assessment. Donepezil was used as positive control and was effective in both models at 1 mg/kg, i.p. Results: Animals treated with NAR and RUT at 50 and 100 mg/kg, p.o. spent significantly more time exploring novel object compared to familiar one, whereas control animals spent almost equal time with both objects in choice trial. NAR and RUT dose-dependently increased recognition and discriminative indices in time-induced long-term as well as scopolamine-induced short-term episodic memory deficit models without interfering with the locomotor activity. Conclusion:We conclude that, NAR and RUT averted both short- and long-term episodic memory deficits in Wistar rats, which may be potential interventions for neurodegenerative diseases as well as chemobrain condition.

Rutin protects against neuronal damage in vitro and ameliorates doxorubicin-induced memory deficits in vivo in Wistar rats

Doxorubicin (DOX) is the most widely used broad-spectrum anticancer agent, either alone or in combination, for most cancers including breast cancer. Long-term use of chemotherapeutic agents to treat breast cancer patients results in cognitive complications with a negative impact on survivors’ quality of life. The study objective was to evaluate rutin (RUT) for its neuroprotective effect against DOX in human neuroblastoma (IMR32) cells in vitro and study its potential to ameliorate DOX-induced cognitive dysfunction in Wistar rats. Cell viability assay (3-[4,5 dimethyl thiazol-2-yl]-2,5-diphenyl tetrazolium bromide), neurite growth assay, detection of apoptosis by (acridine orange/ethidium bromide) staining, intracellular reactive oxygen species (ROS) assay, and flowcytometric analysis were carried out to assess neuroprotective potential against DOX. An in vivo study was conducted for assessing protective effect of RUT against memory deficit associated with DOX-induced chemobrain using object recognition task (ORT). Locomotion was assessed using open field test. Serum biochemistry, acetylcholinesterase, oxidative stress markers in hippocampus, and frontal cortex were assessed. Histopathological analysis of major organ systems was also carried out. Prior exposure to RUT at 100 µM protected IMR32 cells from DOX (1 µM) neurotoxicity. DOX exposure resulted in increased cellular death, apoptosis, and intracellular ROS generation with inhibition of neurite growth in differentiated IMR32 cells, which was significantly ameliorated by RUT. Cognitive dysfunction was induced in Wistar rats by administering ten cycles of DOX (2.5 mg/kg, intra-peritoneal, once in 5 days), as we observed significant impairment of episodic memory in ORT. Coadministration with RUT (50 mg/kg, per os) significantly prevented memory deficits in vivo without any confounding influence on locomotor activity. RUT also offered protection against DOX-induced myelosuppression, cardiotoxicity, and nephrotoxicity. In conclusion, RUT may be a possible adjuvant therapeutic intervention to alleviate cognitive and other complications associated with DOX chemotherapy.

Effect of insulin on spatial memory in aluminum chloride-induced dementia in rats

Latest reports suggest the involvement of insulin in modulating memory. A few published in-vitro studies favor the antidementia effect of insulin. Thus, the present study aimed to evaluate the prophylactic role of insulin and its combination with glucose and its possible mechanism(s) in an aluminum chloride (AlCl3)-induced cognitive dysfunction model in rodents, with a special focus on memory centers namely, the hippocampus and the frontal cortex. Male Wistar rats were exposed to AlCl3 (175 mg/kg orally) for 60 days. Insulin (0.5 IU/kg), Insulin (0.5 IU/kg) in combination with glucose (200 mg/kg), and rivastigmine (1 mg/kg) were administered intraperitoneally 45 min before the administration of AlCl3 for 60 days. Spatial memory was assessed using the Morris water-maze test. After 60 days of treatment, animals were killed, and the hippocampus and frontal cortex were collected and analyzed for acetylcholinesterase activity and antioxidant enzyme level. Blood glucose levels were also analyzed. Treatment with the standard drug, rivastigmine (1 mg/kg), produced a significant reduction in escape latency and increased the time spent in the target quadrant compared with the AlCl3-treated group. Insulin and its combination with glucose could not inhibit the behavioral impairments in aluminum-exposed rats. Treatment with insulin alone and its combination with glucose reversed the increased glucose levels. Insulin alone and its combination with glucose could not inhibit aluminum-induced oxidative stress and impaired cholinergic transmission in the hippocampus and frontal cortex regions. The study suggests the inability of prophylactic insulin administration against cognitive dysfunction induced by environmental toxin (AlCl3) in the hippocampus and the frontal cortex.

Protective Effects of Aqueous Extract of Solanum nigrum Linn. Leaves in Rat Models of Oral Mucositis

Oral mucositis is one of the most debilitating side effects in patient undergoing chemotherapy or chemoradiotherapy. Leaves of the plant Solanum nigrum are used in folklore medicine to treat oral ulcers in India. However, no pharmacological investigation has been carried out till date. Aqueous extract of Solanum nigrum leaves (AESN) was prepared and subjected to various phytochemical screening. HPLC analysis of the ethyl acetate fraction was carried out. The aqueous extract (100 and 200 mg/kg) was further evaluated for its protective effect on two rat models: (a) busulfan plus infrared radiation (chemoradiotherapy) induced oral mucositis and (b) methotrexate (chemotherapy) induced oral mucositis. Various parameters including body weight change, food intake, and mortality were measured. AESN showed protective effect in both models of oral mucositis; however, the higher dose was more effective in chemotherapy induced oral mucositis. A reduction in oral mucositis score (P < 0.05) was observed in the treatment groups. Significant (P < 0.05) improvement in food intake was also observed in AESN treated groups. Aqueous extract of Solanum nigrum leaves has protective effect on chemotherapy and chemoradiotherapy induced oral mucositis in rats.

Insulin Combined with Glucose Improves Spatial Learning and Memory in Aluminum Chloride−Induced Dementia in Rats

Therapeutic intervention using drugs against Alzheimer disease is curative clinically. At present, there are no reports on the curative role of insulin in chronic models of dementia. We evaluated the curative role of insulin and its combination with glucose in dementia. We also investigated the impact of treatments on blood glucose to correlate with cognitive deficit. Further, we analyzed the interaction of treatments with the cholinergic system and oxidative stress in memory centers (i.e., hippocampus and frontal cortex). The antidementia activity of insulin was assessed against aluminum chloride (AlCl3)-induced dementia in rats. Behavioral parameters (Morris water maze test) along with biochemical parameters (Hippocampus and frontal cortex) such as acetylcholinesterase (AChE), catalase, and glutathione (GSH) levels were assessed to correlate cognitive function with cholinergic transmission and oxidative stress. Rats administered insulin and glucose showed improved cognitive function in the Morris water maze test. The combination corrected the diminished level of antioxidant enzymes such as catalase and GSH in the hippocampus and frontal cortex.Combined administration of insulin and glucose to aluminum-treated rats did not inhibit the aluminum action on the acetylcholinesterase enzyme. No significant changes were observed in blood glucose levels between the treatment groups.

Insulin protects against brain oxidative stress with an apparent effect on episodic memory in doxorubicin-induced cognitive dysfunction in wistar rats

The present study was aimed at assessing the protective effect of insulin against doxorubicin (DOX)-induced cognitive dysfunction in Wistar rats. Cognitive function for episodic memory was assessed by a novel object recognition task (NORT) in male Wistar rats. Oxidative stress markers-SOD, catalase, glutathione, and lipid peroxidation-in the hippocampus and frontal cortex were assessed using colorimetric methods. Doxorubicin treatment (2.5 mg/kg, i.p., every 5 days for 50 days) reduced recognition and discriminative indices in NORT with increased oxidative stress in the brain. A nonhypoglycemic dose of insulin (0.5 IU/kg, i.p.) significantly reduced brain oxidative stress (MDA) induced by doxorubicin with an increase in the antioxidant defense systems (SOD, catalase, and GSH). Rats treated with combined insulin and DOX spent comparatively more time with the novel object when compared to the non-novel objects; however, the observed difference was not statistically significant. An apparent improvement (p < 0.26) in recognition of the novel object was observed against the damage induced by doxorubicin. These results suggest that insulin reduces brain oxidative stress and apparently improves doxorubicin-induced cognitive dysfunction in Wistar rats.

Sodium valproate enhances doxorubicin-induced cognitive dysfunction in Wistar rats.

BACKGROUND Increasing number of scientific reports have highlighted the role of histone acetylation/deacetylation in neurodegenerative conditions, including chemotherapy-induced cognitive dysfunction (also known as chemobrain). Multiple sources state that increased activity of histone deacetylases (HDACs) play a detrimental role in chemobrain. In the present study, sodium valproate, a well-known HDAC inhibitor, was explored for its neuroprotective potential against chemobrain development. METHODS Doxorubicin (DOX), a chemotherapeutic agent, was used to induce chemobrain in experimental animals while treating with sodium valproate simultaneously. The animals were subjected to novel object recognition test (NORT) in order to assess their cognitive status and further, brain antioxidant levels were estimated. The animal body weights and survival were noted throughout the period of the study. Blood parameters such as red blood cell count, white blood cell count and haemoglobin levels were also measured. RESULTS Our findings are in contradiction to the known neuroprotective properties of valproic acid. We observed that sodium valproate failed to prevent chemobrain development in DOX treated animals. In fact, treatment with sodium valproate dose dependently worsened cognitive status in DOX treated animals including their brain antioxidant status, possibly leading to neuronal damage through free radical induced toxicity. CONCLUSION The present study highlights the caution that needs to be exercised in projecting HDAC inhibitors as in vivo neuroprotective agents, due to the complexity of existing neurological pathways and the diverse roles of histone deacetylases.

Female rats induced with mammary cancer as a relevant animal model for doxorubicin-induced chemobrain in vivo.

Dear Editor, In recent years, the negative effects of cancer and cancer related treatments on cognition have gained attention. Due to the remarkable increase in survival rates, the focus is on cancer survivorship. Clinically, adjuvant chemotherapy is given, when mammary cancer is diagnosed. Moreover, literature reveals that breast cancer by itself may have influential effects on cognitive behaviour. Hence, it is of the utmost importance to evaluate the potential of chemotherapeutic agents to induce chemobrain in cancerbearing animals. In our previous communication, we demonstrated that healthy female rats can be used to assess a doxorubicin (DOX)induced chemobrainlike condition with impaired episodic memory.1 The study indicated that regardless of the oestrus cycle, female rats could be used as a relevant model for DOXinduced cognitive dysfunction. However, the study was conducted in normal healthy female rats treated either with DOX or vehicle. Clinically, in breast cancer survivors, the cognitive impairment is attributed to both usage of chemotherapeutic agents and progression and metastasis of breast tumour in the patients.2,3 There can be no denying the possibility of new molecules showing activity in DOXinduced cognitive dysfunction by compensating the cytotoxic action of DOX in cancer cells. Hence, experiments were conducted to verify the cognitive dysfunction induced by DOX in female rats being treated for mammary carcinoma. Ideally, human breast tumours transplanted into immunocompromised animals would be an appropriate model to induce mammary carcinoma. However, testing for neurocognitive behavioural analysis requires animals to be exposed to external environment for prolonged periods. Sterility, a primary prerequisite for the maintenance of immunocompromised (nude) rodents is practically not feasible. Literature supports the fact that cytokines have direct influential effects on learning processes.4 Hence, deficiency of circulating cytokine levels and their regulated immune responses in immunocompromised animals, will alter cognition in them. Transplantable cancer models are not feasible in all laboratories, since it requires special specifications to maintain immunocompromised animals. Therefore, we induced mammary carcinoma by NmethylNnitrosourea (NMU) in female rats followed by DOX treatment. All the experimental protocols were approved by Institutional Animal Ethics Committee. Female Sprague Dawley rats were maintained under standard husbandry conditions at Central Animal Research facility of Manipal University. A day prior to, and during the experiments, food intake was restricted to 80% to improve their locomotor activity. Rats were broadly divided into healthy and NMUinjected groups. In the second instance, rats received NMU (50 mg/kg, intraperitoneally (i.p.)) injection at age of 30–35 d. Development of mammary carcinoma was confirmed after 8–10 wk. Based on this, two groups of animals were made for each category, namely, the control group (WFI, i.p.) and the DOXtreated group (2.5 mg/kg, i.p.; once every 5 d for 50 d). Cognitive function was assessed in all the animals using novel object recognition and Morris water maze tasks.5,6 In the novel object recognition task (NORT), recognition (RI) and discriminative indices (DI) were calculated which relates to episodic memory. In the Morris water maze test, Q4 time during retention learning was calculated to determine the spatial memory in rats. Along with cognitive function, the prognosis of mammary carcinoma was monitored by measuring the tumour volume of mammary pad. Difference in means between various treatments for RI and DI were compared using KruskalWallis test followed by Dunn’s posthoc test. Latency time in returning to Q4 quadrant and tumour volume were compared by oneway ANOVA followed by Bonferroni’s test using Prism software trial version 6.05 (GraphPad Software, La Jolla, CA, USA). Doxorubicin significantly reduced RI (Fig. 1a) and DI (Fig. 1b) as compared to its vehicle control, while in the Morris water maze test, DOX treatment did not significantly alter the time to return to the Q4 quadrant (Fig. 1c). This suggests that DOX treatment can impair episodic, but not spatial memory in NMU untreated rats. In NMU treated rats, DOX treatment significantly decreased RI (Fig. 1a), DI (Fig. 1b), time to return to the Q4 quadrant (Fig. 1c), and tumour volume (Fig. 1d), indicating the cytotoxic drug affects both episodic and spatial memory, with a reduction in intensity of mammary carcinoma with respect to DOXuntreated mammary carcinoma rats. In addition, histology of major organs (stomach, liver, kidney, brain, bone and bone marrow) did not reveal the presence of any primary or secondary tumours. Both episodic and semantic memory in humans is affected after chemotherapy. DOX treatment impaired only episodic memory in the healthy rats. However, in the tumour model, DOX treatment resulted in impairment of episodic and spatial memory which is seen clinically after chemotherapy. Therefore, the model described in this study is more appropriate than the previously reported one for screening of newer molecules for chemobrain condition.1