Centella asiatica (CA) herb is a traditional medicine, long reputed to provide cognitive benefits. We have reported that CA water extract (CAW) treatment improves cognitive function of aged Alzheimer’s disease (AD) model Tg2576 and wild-type (WT) mice, and induces an NRF2-regulated antioxidant response in aged WT mice. Here, CAW was administered to AD model 5XFAD female and male mice and WT littermates (age: 7.6 +/ − 0.6 months), and object recall and contextual fear memory were tested after three weeks treatment. CAW’s impact on amyloid-β plaque burden, and markers of neuronal oxidative stress and synaptic density, was assessed after five weeks treatment. CAW antioxidant activity was evaluated via nuclear transcription factor (erythroid-derived 2)-like 2 (NRF2) and NRF2-regulated antioxidant response element gene expression. Memory improvement in both genders and genotypes was associated with dose-dependent CAW treatment without affecting plaque burden, and marginally increased synaptic density markers in the hippocampus and prefrontal cortex. CAW treatment increased Nrf2 in hippocampus and other NRF2 targets (heme oxygenase-1, NAD(P)H quinone dehydrogenase 1, glutamate-cysteine ligase catalytic subunit). Reduced plaque-associated SOD1, an indicator of oxidative stress, was observed in the hippocampi and cortices of CAW-treated 5XFAD mice. We postulate that CAW treatment leads to reduced oxidative stress, contributing to improved neuronal health and cognition.

Centella asiatica is a medicinal plant used to enhance memory. We have previously shown that a water extract of Centella asiatica (CAW) attenuates β-amyloid (Aβ)-induced spatial memory deficits in mice and improves neuronal health. Yet the effect of CAW on other cognitive domains remains unexplored as does its In vivo mechanism of improving Aβ-related cognitive impairment. This study investigates the effects of CAW on learning, memory and executive function as well as mitochondrial function and antioxidant response in the 5×FAD model of Aβ accumulation. Seven month old 5×FAD female mice were treated with CAW (2mg/mL) in their drinking water for two weeks prior to behavioral testing. Learning, memory and executive function were assessed using the object location memory task (OLM), conditioned fear response (CFR) and odor discrimination reversal learning (ODRL) test. Mitochondrial function was profiled using the Seahorse XF platform in hippocampal mitochondria isolated from these animals and tissue was harvested for assessment of mitochondrial, antioxidant and synaptic proteins. CAW improved performance in all behavioral tests in the 5×FAD but had no effect on WT animals. Hippocampal mitochondrial function was improved and hippocampal and cortical expression of mitochondrial genes was increased in CAW-treated 5×FAD mice. Gene expression of the transcription factor NRF2, as well as its antioxidant target enzymes, was also increased with CAW treatment in both WT and 5×FAD mice. CAW treatment also decreased Aβ-plaque burden in the hippocampus of treated 5×FAD mice but had no effect on plaques in the cortex. These data show that CAW can improve many facets of Aβ-related cognitive impairment in 5×FAD mice. Oral treatment with CAW also attenuates hippocampal mitochondrial dysfunction in these animals. Because mitochondrial dysfunction and oxidative stress accompany cognitive impairment in many pathological conditions beyond Alzheimer’s disease, this suggests potentially broad therapeutic utility of CAW.

Introduction Centella asiatica is a plant used for centuries to enhance memory. We have previously shown that a water extract of Centella asiatica (CAW) attenuates age‐related spatial memory deficits in mice and improves neuronal health. Yet the effect of CAW on other cognitive domains remains unexplored as does its mechanism of improving age‐related cognitive impairment. This study investigates the effects of CAW on a variety of cognitive tasks as well as on synaptic density and mitochondrial and antioxidant pathways.MethodsTwenty‐month‐old CB6F1 mice were treated with CAW (2 mg/ml) in their drinking water for 2 weeks prior to behavioral testing. Learning, memory, and executive function were assessed using the novel object recognition task (NORT), object location memory task (OLM), and odor discrimination reversal learning (ODRL) test. Tissue was collected for Golgi analysis of spine density as well as assessment of mitochondrial, antioxidant, and synaptic proteins.ResultsCAW improved performance in all behavioral tests suggesting effects on hippocampal and cortical dependent memory as well as on prefrontal cortex mediated executive function. There was also an increase in synaptic density in the treated animals, which was accompanied by increased expression of the antioxidant response gene NRF2 as well as the mitochondrial marker porin.ConclusionsThese data show that CAW can increase synaptic density as well as antioxidant and mitochondrial proteins and improve multiple facets of age‐related cognitive impairment. Because mitochondrial dysfunction and oxidative stress also accompany cognitive impairment in many pathological conditions this suggests a broad therapeutic utility of CAW.

Centella asiatica (CA) is an edible plant and a popular botanical dietary supplement. It is reputed, in Ayurveda, to mitigate age-related cognitive decline. There is a considerable body of preclinical literature supporting CA’s ability to improve learning and memory. This study evaluated the contribution of CA’s triterpenes (TT), widely considered its active compounds, and caffeoylquinic acids (CQA) to the cognitive effects of CA water extract (CAW) in 5XFAD mice, a model of Alzheimer’s disease. 5XFAD mice were fed a control diet alone, or one containing 1% CAW or compound groups (TT, CQA, or TT + CQA) equivalent to their content in 1% CAW. Wild-type (WT) littermates received the control diet. Conditioned fear response (CFR) was evaluated after 4.5 weeks. Female 5XFAD controls showed no deficit in CFR compared to WT females, nor any effects from treatment. In males, CFR of 5XFAD controls was attenuated compared to WT littermates (p = 0.005). 5XFAD males receiving CQA or TT + CQA had significantly improved CFR (p < 0.05) compared to 5XFAD male controls. CFR did not differ between 5XFAD males receiving treatment diets and WT males. These data confirm a role for CQA in CAW’s cognitive effects.

Centella asiatica has been used for centuries to enhance memory. We have previously shown that a water extract of Centella asiatica (CAW) protects against the deleterious effects of amyloid-β (Aβ) in neuroblastoma cells and attenuates Aβ-induced cognitive deficits in mice. Yet, the neuroprotective mechanism of CAW has yet to be thoroughly explored in neurons from these animals. This study investigates the effects of CAW on neuronal metabolism and oxidative stress in isolated Aβ-expressing neurons. Hippocampal neurons from amyloid precursor protein overexpressing Tg2576 mice and wild-type (WT) littermates were treated with CAW. In both genotypes, CAW increased the expression of antioxidant response genes which attenuated the Aβ-induced elevations in reactive oxygen species (ROS) and lipid peroxidation in Tg2576 neurons. CAW also improved mitochondrial function in both genotypes and increased the expression of electron transport chain enzymes and mitochondrial labeling, suggesting an increase in mitochondrial content. These data show that CAW protects against mitochondrial dysfunction and oxidative stress in Aβ-exposed hippocampal neurons which could contribute to the beneficial effects of the extract observed in vivo. Since CAW also improved mitochondrial function in the absence of Aβ, these results suggest a broader utility for other conditions where neuronal mitochondrial dysfunction occurs.