Neuroprotective effect of nose-to-brain delivery of Asiatic acid in solid lipid nanoparticles and its mechanisms against memory dysfunction induced by Amyloid Beta1-42 in mice.

BACKGROUND: Amyloid-ß1-42 (Aß1-42) plays an essential role in the development of the early stage of Alzheimer's disease (AD). Asiatic acid (AA), an active compound in Centella asiatica L, exhibit neuroprotective properties in previous studies. Due to its low bioavailability, the nose-to-brain delivery technique was used to enhance AA penetration in the brain. In this study, AA was also loaded in solid lipid nanoparticles (SLNs) as a strategy to increase its absorption in the nasal cavity. METHODS: Memory impairment was induced via direct intracerebroventricular injection of Aß1-42 oligomer into mouse brain. The neuroprotective effect and potential underlying mechanisms were investigated using several memory behavioral examinations and molecular techniques. RESULTS: The intranasal administration of AA in SLNs attenuated learning and memory impairment induced by Aß1-42 in Morris water maze and novel object recognition tests. AA significantly inhibited tau hyperphosphorylation of pTau-S396 and pTau-T231 and prevented astrocyte reactivity and microglial activation in the hippocampus of Aß1-42-treated mice. It is also decreased the high levels of IL-1ß, TNF-α, and malondialdehyde (MDA) in mouse brain. CONCLUSIONS: These results suggested that nose-to-brain delivery of AA in SLNs could be a promising strategy to treat the early stage of AD.

Modulation of Neuronal Activity on Intercalated Neurons of Amygdala Might Underlie Anxiolytic Activity of a Standardized Extract of Centella asiatica ECa233.

GABAergic intercalated neurons of amygdala (ITCs) have recently been shown to be important in the suppression of fear-like behavior. Effects of ECa233 (a standardized extract of Centella asiatica), previously demonstrated anxiolytic activity, were then investigated on ITCs. Cluster of GABAergic neurons expressing fluorescence of GFP was identified in GAD67-GFP knock-in mice. We found that neurons of medial paracapsular ITC were GABAergic neurons exhibiting certain intrinsic electrophysiological properties similar to those demonstrated by ITC neurons at the same location in C57BL/6J mice. Therefore, we conducted experiments in both C57BL/6J mice and GAD67-GFP knock-in mice. Excitatory postsynaptic currents (EPSCs) were evoked by stimulation of the external capsule during the whole cell patch-clamp recordings from ITC neurons in brain slices. ECa233 was found to increase the EPSC peak amplitude in the ITC neurons by about 120%. The EPSCs in ITC neurons were completely abolished by the application of an AMPA receptor antagonist. Morphological assessment of the ITC neurons with biocytin demonstrated that most axons of the recorded neurons innervated the central nucleus of the amygdala (CeA). Therefore, it is highly likely that anxiolytic activity of ECa233 was mediated by increasing activation, via AMPA receptors, of excitatory synaptic input to the GABAergic ITC leading to depression of CeA neurons.

Neuroprotective effect of a standardized extract of Centella asiatica ECa233 in rotenone-induced parkinsonism rats.

BACKGROUND: Mitochondrial dysfunction and reactive oxygen species (ROS) generation cause dopaminergic neurodegeneration in Parkinson's disease. The neuroprotective approach is a promising strategy to slow disease progression in Parkinson's disease. A standardized extract of Centella asiatica ECa233 has been previously reported to have pharmacological effects in the central nervous system. PURPOSE: This study aimed to determine the neuroprotective effect and mechanisms of ECa233 in rotenone-induced parkinsonism rats. METHODS: Rats were orally given either vehicle or ECa233 (10, 30 and 100 mg/kg) for 20 consecutive days. Rotenone (2.5 mg/kg i.p.) was given to parkinsonism (PD) and ECa-treated rats from day 15 to 20. Locomotor activity was recorded on day 1, 14, 17 and 20. Tyrosine-hydroxylase (TH) immunohistological staining was used to determine dopaminergic neurons in the substantia nigra and striatum. Furthermore, mitochondrial complex I activity, malondialdehyde (MDA) levels, superoxide dismutase (SOD) and catalase protein expression were measured in brain tissue. RESULTS: Rats receiving ECa233 30 mg/kg showed a significant increase in distances (p < 0.01) together with a higher number and intensity of dopaminergic neurons in the substantia nigra and striatum (p < 0.001) compared to PD rats. ECa233 (30 mg/kg) protected against mitochondrial complex I inhibition, decreased MDA levels (p < 0.05) and increased SOD (p < 0.01) and catalase (p < 0.05) expression. CONCLUSION: ECa233 can protect against rotenone-induced motor deficits and dopaminergic neuronal death. These effects are mediated through the protection of mitochondrial complex I activity, the effects of antioxidants and the enhancement of antioxidant enzyme expression.

Reorganization of sensory pathways after neonatal hemidecortication in rats.

We investigated ascending somatosensory pathways in neonatally hemidecorticated rats. Injection of an anterograde tracer, biotinylated dextran amine (BDA), into the contralesional dorsal root ganglions revealed ipsilateral projections to the dorsal column nuclei (DCN) in hemidecorticated rats as well as in normal rats. Injection of BDA into the DCN on the same side revealed that while most axons projected to the contralateral thalamus, some axons were detected in the ipsilateral thalamus in hemidecorticated rats while such projections were rarely detected in normal rats. The results suggest that aberrant ipsilateral projections of DCN neurons contralateral to the lesion developed after the hemidecortication.

Neuritogenic effect of standardized extract of Centella asiatica ECa233 on human neuroblastoma cells.

BACKGROUND: In order to gain insight into neuroprotective effects of ECa 233, a standardized extract of Centella asiatica, previously demonstrated in animal models of memory impairment induced by transient global ischemia or intracerebroventricular injection of ß-amyloid, the effect of ECa 233 on neurite outgrowth of human IMR-32 neuroblastoma cell line was investigated. METHODS: Cells were seeded and incubated with various concentrations of ECa 233. Morphometric analysis was carried out by a measurement of the longest neurite growth of cells at 24 and 48 h. Contributing signaling pathways possibly involved were subsequently elucidated by western blot analysis. RESULTS: While ECa 233 had only limited effects on cell viability, it significantly enhanced neurite outgrowth of IMR-32 cells at the concentrations of 1-100 µg/ml. Western blot analysis revealed that ECa 233 significantly upregulated the level of activated ERK1/2 and Akt of the treated cells suggesting their involvement in the neuritogenic effect observed, which was subsequently verified by the finding that an addition of their respective inhibitors could reverse the effect of ECa 233 on these cells. CONCLUSIONS: The present study clearly demonstrated neurite outgrowth promoting activity of ECa 233. ERK1/2 and Akt signaling pathways seemed to account for the neurotrophic effect observed. In conjunction with in vivo neuroprotective effect of ECa 233 previously reported, the results obtained support further development of ECa 233 for clinical use in neuronal injury or neurodegenerative diseases.