Function In Middle-aged Rats Research Articles

Centella asiatica improves memory and executive function in middle-aged rats by controlling oxidative stress and cholinergic transmission

Ethnopharmacological relevanceCentella asiatica (L.) Urban, is a medicinal herb with rich history of traditional use in Indian subcontinent. This herb has been valued for its diverse range of medicinal properties including memory booster, and also as a folk treatment for skin diseases, wound healing and mild diuretic. Aim of studyAging is a gradual and continuous process of natural decay in the biological systems, including the brain. This work aims to evaluate the effectiveness of ethanolic extract of Centella asiatica (CAE) on age-associated cognitive impairments in rats, as well as the underlying mechanism. Material and methodsRats were allocated into five distinct groups of 5 animals each: Young rats (3 months old rats), middle-aged (m-aged) rats (13–14 months old), and the remaining three groups were comprised of m-aged rats treated with different concentrations of CAE, viz., 150, 300, and 450 mg/kg b. w., orally for 42 days. Y-maze, open field, novel object recognition, and elevated plus maze tests were used to assess animal behavior. The malondialdehyde (MDA), superoxide dismutase (SOD), and acetylcholinesterase (AChE) assays; and H&E staining were done in the rat brain to assess the biochemical and structural changes. CAE was also subjected to HPLC analysis, in vitro antioxidant and anti-cholinergic activity. The active compounds of CAE were docked with AChE and BuChE in molecular docking study. ResultsThe results showed that CAE treatment improves behavioral performance; attenuates the age-associated increase in MDA content, SOD, and AChE activity; and reduces neuronal loss. In vitro study showed that CAE has concentration-dependent antioxidant and anti-AChE activity. Furthermore, the presence of Asiatic acid and Madecassic acid in CAE and their good binding with cholinergic enzymes (in silico) also suggest the anticholinergic effect of CAE. ConclusionThe findings of the current study show that the anticholinergic and antioxidant effects of CAE are attributable to the presence of Asiatic acid and Madecassic acid, which not only provide neuroprotection against age-associated cognitive decline but also reverse it.

Abstract TMP113: Conditional Expression Of Mir-20a-3p In Neurons Versus Astrocytes And Its Impact On Acute Stroke Outcomes

Introduction: MiR-20a-3p was found to be upregulated in the brains of adult female rats, who typically sustain smaller infarcts, compared to that of middle-aged rats, who typically sustain larger infarcts. In fact, qRT-PCR analysis shows that miR-20a-3p is profoundly upregulated (>240,000-fold elevation) in adult astrocytes post-stroke, while ischemic neurons do not exhibit this upregulation. Intravenous injections of miR-20a-3p mimic, given 4h after stroke, reduced infarct size and improved sensory motor function in middle-aged rats, and surprisingly exogenous miR-20a-3p was preferentially taken up by neurons . To better understand the cellular target of this miRNA, we compared the efficacy of conditional expression of miR-20a-3p in neurons versus astrocytes in improving acute stroke outcomes. Methods: Two viral vectors to conditionally express miR-20a-3p in neurons (rAAV5-TetOn-NSE-miR-20a-3p-mCherry) and astrocytes (rAAV5-TetOn-GFAP-miR-20a-3p-mCherry) were injected into the striatum of middle-aged female rats.Control subjects were given an identical vector minus miR-20a-3p. After 6 weeks, the rats were subjected to middle cerebral artery occlusion, and the virus was activated by i.p. doxycycline 4h post-stroke. Behavioral assessments were performed at 2d and 5d. Animals were terminated at 5d, and infarct size was assessed. Results: Astrocytic miR-20a-3p improved survival compared to control (p=0.0372), and neuronal miR-20a-3p showed a trend for improved survival (p=0.0805). Neuronal miR-20a-3p reduced latency on the adhesive removal task at 2d and 5d, while astrocytic miR-20a-3p demonstrated modest improvement only at 5d. Moreover, neuronal miR-20a-3p significantly reduced infarct size relative to control (p=0.0087), while astrocytic miR-20a-3p did not improve infarct size(p=0.1117). Conclusions: Both rAAVs resulted in improvement in stroke outcomes; however, the results from the neuronal vector were much more robust. The fact that astrocytes upregulate miR-20a-3p after stroke yet neurons more efficiently use the miRNA to improve stroke outcome suggest that this miRNA may be transferred from astrocytes to neurons to confer neuroprotection. Supported by RFAG042189 to FS and 1F31NS118970-01A to TEB.

Exercise training causes a partial improvement through increasing testosterone and eNOS for erectile function in middle-aged rats.

Aging changes the balance of sex hormones and causes endothelial dysfunction in the penis, both of which are important determinants of erectile dysfunction (ED). The purpose of this study was to evaluate whether exercise training could protect against erectile dysfunction by increasing serum testosterone and penile eNOS levels in aging rats. A total of 14 young (2-month-old) and 14 middle-aged (18-month-old) Sprague Dawley rats were randomly assigned to either untrained control (young control, [YC], middle-aged control, [MC]) or endurance exercise-trained (young exercise, [YE], middle-aged exercise, [ME]) groups with seven rats per group. The exercise groups trained with treadmill running for 6 weeks. Body composition parameters (body weight, heart mass, liver mass, and testicular mass), serum sex hormone levels (testosterone, luteinizing hormone, follicle-stimulating hormone, and prolactin), endothelial function-related parameters in the penis (endothelial nitric oxide synthase [eNOS], CD31, alpha smooth muscle actin [α-SMA]), and maximal intracavernous pressure measure (ICP) and total ICP were analyzed in middle-aged rats. The middle-aged groups showed increased body weight, as compared with the young groups, but exercise training attenuated the aging-induced increase in body weight. The middle-aged groups had lower testicular mass compared with the young groups, but exercise training attenuated aging-induced decreases in testicular mass. Exercise training increased serum testosterone levels in both the young and middle-aged groups. However, there were no changes in the levels of luteinizing hormone, follicle-stimulating hormone, and prolactin among the groups. MC group showed decreased protein levels of p-eNOS, as compared with the YC group. However, exercise training protected against aging-induced decrease in eNOS and p-eNOS protein levels in the penis. Interestingly, exercise training also increased protein levels of α-SMA and maximal ICP in the middle-aged group. Exercise training has beneficial effects on erectile function in aged rats through increased testosterone production from the testis and strengthening of the cavernous endothelium with activation of eNOS. Therefore, exercise training may be a therapeutic modality for improving erectile dysfunction associated with aging.

Repeated treatment with the α2-adrenoceptor agonist UK-14304 improves cognitive performance in middle-age rats: Role of hippocampal Fas-associated death domain.

The cell fate regulator Fas-associated death domain (FADD) balances cell death with non-apoptotic actions via its phosphorylated form. A recent study associated loss of cortical FADD with cognitive decline and increased risk of clinical dementia. Since the activation of cortical α2A-adrenoceptors improved memory deficits in various animal models of working memory loss, the present study evaluated whether UK-14304, an α2-adrenoceptor agonist known to acutely regulate brain FADD forms, would improve cognitive function in middle-aged rats. Sprague-Dawley rats were treated with UK-14304 (0.3 or 1 mg/kg) or saline (1 mL/kg) for seven days. Cognitive performance was evaluated in the eight-arm radial maze. FADD protein content was measured in the prefrontal cortex and hippocampus by Western blot analysis. The results showed that UK-14304 (1 mg/kg) improved cognitive performance (less time: -310±45 s, p=0.025 and fewer errors: -2.75±1.06, p=0.043 to complete the maze) and increased FADD selectively in the hippocampus (+35±11%, p=0.029). Interestingly, hippocampal FADD content negatively correlated with the time ( r=-0.651, p<0.01) needed to complete the maze. Thus, better cognitive scores were associated with higher FADD hippocampal content. These results support a role for α2-adrenoceptors in ameliorating cognition and suggest FADD protein content as a possible correlate for cognitive performance.

Diabetes Mellitus Impairs Cognitive Function in Middle-Aged Rats and Neurological Recovery in Middle-Aged Rats After Stroke

Diabetes mellitus (DM) is a common metabolic disease among the middle-aged and older population, which leads to an increase of stroke incidence and poor stroke recovery. The present study was designed to investigate the impact of DM on brain damage and on ischemic brain repair after stroke in aging animals. DM was induced in middle-aged rats (13 months) by administration of nicotinamide and streptozotocin. Rats with confirmed hyperglycemia status 30 days after nicotinamide-streptozotocin injection and age-matched non-DM rats were subjected to embolic middle cerebral artery occlusion. Middle-aged rats subjected to nicotinamide-streptozotocin injection became hyperglycemic and developed cognitive deficits 2 months after induction of DM. Histopathologic analysis revealed that there was sporadic vascular disruption, including cerebral microvascular thrombosis, blood-brain barrier leakage, and loss of paravascular aquaporin-4 in the hippocampi. Importantly, middle-aged DM rats subjected to stroke had exacerbated sensorimotor and cognitive deficits compared with age-matched non-DM ischemic rats during stroke recovery. Compared with age-matched non-DM ischemic rats, DM ischemic rats exhibited aggravated neurovascular disruption in the bilateral hippocampi and white matter, suppressed stroke-induced neurogenesis and oligodendrogenesis, and impaired dendritic/spine plasticity. However, DM did not enlarge infarct volume. Our data suggest that DM exacerbates neurovascular damage and hinders brain repair processes, which likely contribute to the impairment of stroke recovery.

Sex-related differences in intrinsic myocardial properties influence cardiac function in middle-aged rats during infarction-induced left ventricular remodeling.

We previously determined that residual left ventricular (LV) myocardium of middle‐aged rats had sex‐related differences in regional tissue properties 4 weeks after a large myocardial infarction (MI). However, the impact of such differences on cardiac performance remained unclear. Therefore, our current study aimed to elucidate whether sex‐related changes in MI‐induced myocardial remodeling can influence cardiac function. A similar‐sized MI was induced in 12‐month‐old male (M‐MI) and female (F‐MI) Sprague–Dawley rats by ligation of the left coronary artery. The cardiac function was monitored for 2 months after MI and then various LV parameters were compared between sexes. We found that although two sex groups had a similar pattern of MI‐induced decline in LV function, F‐MI rats had greater cardiac performance compared to M‐MI rats, considering the higher values of EF (39.9 ± 3.4% vs. 26.7 ± 7.7%, P < 0.05), SW index (40.4 ± 2.1 mmHg • mL/kg vs. 20.2 ± 3.3 mmHg • mL/kg, P < 0.001), and CI (139.2 ± 7.9 mL/min/kg vs. 74.9 ± 14.7 mL/min/kg, P < 0.01). The poorer pumping capacity in M‐MI hearts was associated with markedly reduced LV compliance and prolonged relaxation. On the tissue level, F‐MI rats revealed a higher, than in M‐MI rats, density of cardiac myocytes in the LV free wall (2383.8 ± 242.6 cells/mm2 vs. 1785.7 ± 55.9 cells/mm2, P < 0.05). The latter finding correlated with a lower density of apoptotic cardiac myocytes in residual LV myocardium of F‐MI rats (0.18 ± 0.08 cells/mm2 vs. 0.91 ± 0.30 cells/mm2 in males, P < 0.01). Thus, our data suggested that F‐MI rats had markedly attenuated decline in cardiac performance compared to males due to ability of female rats to better retain functionally favorable intrinsic myocardial properties.

Age modulates Fe3O4 nanoparticles liver toxicity: dose-dependent decrease in mitochondrial respiratory chain complexes activities and coupling in middle-aged as compared to young rats.

We examined the effects of iron oxide nanoparticles (IONPs) on mitochondrial respiratory chain complexes activities and mitochondrial coupling in young (3 months) and middle-aged (18 months) rat liver, organ largely involved in body iron detoxification. Isolated liver mitochondria were extracted using differential centrifugations. Maximal oxidative capacities (V max, complexes I, III, and IV activities), V succ (complexes II, III, and IV activities), and V tmpd, (complex IV activity), together with mitochondrial coupling (V max/V 0) were determined in controls conditions and after exposure to 250, 300, and 350 μg/ml Fe3O4 in young and middle-aged rats. In young liver mitochondria, exposure to IONPs did not alter mitochondrial function. In contrast, IONPs dose-dependently impaired all complexes of the mitochondrial respiratory chain in middle-aged rat liver: V max (from 30 ± 1.6 to 17.9 ± 1.5; P < 0.001), V succ (from 33.9 ± 1.7 to 24.3 ± 1.0; P < 0.01), V tmpd (from 43.0 ± 1.6 to 26.3 ± 2.2 µmol O2/min/g protein; P < 0.001) using Fe3O4 350 µg/ml. Mitochondrial coupling also decreased. Interestingly, 350 μg/ml Fe3O4 in the form of Fe3+ solution did not impair liver mitochondrial function in middle-aged rats. Thus, IONPs showed a specific toxicity in middle-aged rats suggesting caution when using it in old age.

Sexual experience restores age-related decline in adult neurogenesis and hippocampal function.

Aging is associated with compromised hippocampal function and reduced adult neurogenesis in the dentate gyrus. As new neurons have been linked to hippocampal functions, such as cognition, age-related decline in new neuron formation may contribute to impaired hippocampal function. We investigated whether a rewarding experience known to stimulate neurogenesis in young adult rats, namely sexual experience, would restore new neuron production and hippocampal function in middle-aged rats. Sexual experience enhanced the number of newly generated neurons in the dentate gyrus with both single and repeated exposures in middle-aged rats. Following continuous long-term exposure to sexual experience, cognitive function was improved. However, when a prolonged withdrawal period was introduced between the final mating experience and behavioral testing, the improvements in cognitive function were lost despite the presence of more new neurons. Taken together, these results suggest that repeated sexual experience can stimulate adult neurogenesis and restore cognitive function in the middle-aged rat as long as the experience persists throughout the testing period. The extent to which changes in adult neurogenesis underlie those in cognition remain unknown.

Effect of Long-term Administration of Cordycepin from Cordyceps militaris on Testicular Function in Middle-aged Rats

This study was carried out to examine the potential beneficial effect of cordycepin on the decline of testicular function induced with age. A total of 30 male Sprague-Dawley rats (twenty-four 12-month-olds and six 2-month-olds) were divided into five groups. The young control (YC) and middle-aged control (MC) groups received vehicle only. Cordycepin-treated groups were administered daily doses of oral cordycepin at 5, 10, and 20 mg/kg body weight for 4 months. As a result, the MC group exhibited epididymal weight loss, decreased sperm motility, and reduced spermatogenesis compared to the young control group. Interestingly, the epididymal weights of middle-aged rats were dose-dependently increased by treatment with cordycepin. Cordycepin also improved calcium levels and decreased urea and nitrogen, uric acid, and creatinine in the blood of middle-aged rats. In addition, cordycepin significantly increased sperm motility and the progressiveness of sperm movement. All cordycepin-treated groups showed well-arranged spermatogonia, densely packed cellular material, and increased numbers of mature spermatozoa in the seminiferous lumen compared to the middle-aged control group. These results indicate that long-term administration of cordycepin can counteract the decline of testicular function in middle-aged rats.

Thymoquinone improves aging-related endothelial dysfunction in the rat mesenteric artery

Aging-related endothelial dysfunction is characterized by blunted nitric oxide (NO)- and endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxations in arteries, which may be due, at least in part, to increased oxidative stress. Endothelial dysfunction will promote the initiation and development of major cardiovascular diseases such as atherosclerosis and hypertension. Thymoquinone (TQ) is the most active constituent of the volatile oil of Nigella sativa seeds with well-documented antioxidative properties and vasodilator effects. This study determined whether TQ improves the endothelial function in middle-aged rats. Control young rats (16 weeks) received solvent (ethanol, 3% v/v), and middle-aged rats (46 weeks) either solvent or TQ (10 mg/kg/day) in the drinking water. Mesenteric artery reactivity was determined in organ chambers, vascular oxidative stress by dihydroethidine and MitoSOX staining, and expression of target proteins by immunohistochemical staining. Aging-related blunted NO- and EDHF-mediated responses were associated with downregulation of endothelial NO synthase (eNOS) and calcium-activated potassium channels (SK(Ca) and IK(Ca)) expression. Endothelial dysfunction was also associated with oxidative stress and an upregulation of angiotensin II and AT1 receptor expressions. Intake of TQ for 14 days restored NO- and EDHF-mediated relaxations, normalized oxidative stress, the expression level of eNOS, SK(Ca), IK(Ca), and the components of the angiotensin system in the mesenteric artery of middle-aged rats. Thus, TQ improves endothelial function in aging, at least in part, through inhibition of oxidative stress and normalization of the angiotensin system. TQ may represent a novel therapeutic approach for aging-associated vascular diseases.