Centella asiatica Promotes Antioxidant Gene Expression and Mitochondrial Oxidative Respiration in Experimental Autoimmune Encephalomyelitis

Abstract

Background/Objectives:Centella asiatica (L.) Urban (family Apiaceae) (C. asiatica) is a traditional botanical medicine used in aging and dementia. Water extracts of C. asiatica (CAW) have been used to treat neuropsychiatric symptoms in related animal models and are associated with increases in antioxidant response element (ARE) genes and improvements in mitochondrial respiratory function and neuronal health. Because multiple sclerosis (MS) shares its neurogenerative pathology of oxidative stress and mitochondrial dysfunction with aging and dementia, neuropsychiatric symptoms in MS may also benefit from C. asiatica. To determine whether CAW similarly benefits neuropsychiatric symptoms, ARE gene expression, and mitochondrial respiration in inflammatory models of MS, and to determine the effects of CAW on clinical disability and inflammation, we tested CAW using experimental autoimmune encephalomyelitis (EAE). Methods: C57BL/6J mice induced with EAE were treated with CAW or a placebo for 2 weeks. The outcomes were clinical disability, signs of anxiety (open field test), ARE gene expression, mitochondrial respiration, and inflammation and demyelination. Results: At the dosing schedule and concentrations tested, CAW-treated mice with EAE demonstrated increased ARE gene expression and mitochondrial respiratory activity compared to those of placebo-treated mice with EAE. CAW was also associated with reduced inflammatory infiltrates in the spinal cord, but the differences between the populations of activated versus quiescent microglia were equivocal. CAW did not improve behavioral performance, EAE motor disability, or demyelination. Conclusions: In the inflammatory EAE model of MS, CAW demonstrates similar neuroprotective effects to those it exhibits in aging and dementia mouse models. These benefits, along with the anti-inflammatory effects of CAW, support further investigation of its neuropsychiatric effects in people with MS.

Keywords: Centella asiatica; antioxidant; experimental autoimmune encephalomyelitis; mitochondrial respiration.

Figure 1

(a) Onset and final clinical disability in CAW-treated mice and placebo-treated mice following induction of experimental autoimmune encephalopathy (EAE) were similar between groups in Study 2. Control mice without EAE did not exhibit clinical disability. (b) Center Duration as percent of baseline was greater in CAW-treated mice (less anxiety) than placebo or control cohorts at day 12 (early symptomatic), but not at Study 2’s end. (c) Distance Moved (activity) in Study 2 day 20 was lower in both CAW and placebo groups compared to controls, likely reflecting disability caused by EAE. (d,e) Composite stains for CD3 (green, lymphocytes) and Iba1 (red, activated microglia) are shown with DAPI (blue, DNA) in CAW-treated and placebo-treated EAE mouse sections. (f,g) Decreased CD3 staining in CAW-treated EAE mouse compared to placebo-treated EAE mouse (2.9% STD 1.6% vs. 5.0% STD 1.7%, p = 0.01). (h,i) Trend toward decreased Iba1 staining for activated microglia between CAW- and placebo-treated mice (3.3% STD 2.8% vs. 5.2% STD 5.1%, p = 0.30). (j–l) While both EAE spinal cord sections demonstrate demyelination compared to control, there was no qualitative difference between placebo and CAW. * p < 0.05, ^# p < 0.10.

Figure 2

Fluorescence-activated cell sorting analysis of pooled spinal cord samples of monocyte expression (CD74+) resting (CD11b + CD45low) and activated (CD11b + CD45hi) microglia in brains and spinal cords of mice with experimental autoimmune encephalomyelitis (EAE) treated with Centella asiatica or placebo. Results presented as percentages (%) of total cell count.

Figure 3

Group comparisons of antioxidant response element (ARE) gene expression and mitochondrial respiration, measured as oxygen consumption rate (OCR), results in Studies 1 (n = 4 per group, (a,b)) and 2 (n = 10 per group, (c,d)). While ARE gene expression in cerebral cortices of CAW-treated mice with experimental autoimmune encephalomyelitis (EAE) was not greater than placebo (a), OCR was greater in CAW-treated mice at basal, maximal, and spare capacity endpoints (b). Addition of control group without EAE in Study 2 illustrates ARE gene induction in placebo-treated mice resulting from EAE that is further increased by CAW treatment (c). Addition of control group also demonstrates reduction of OCR values in placebo cohort due to EAE, which were returned to normal with CAW treatment (d). Hmox1, heme oxygenase 1; Gclc, glutamate-cysteine ligase, catalytic subunit; NqO1, NAD(P)H dehydrogenase-quinone oxidoreductase 1; Nrf2, nuclear factor (erythroid-derived 2)-like 2. * p < 0.05, ** p < 0.01, *** p < 0.001.