Curcumin pre-treatment may protect against mitochondrial damage in LRRK2-mutant Parkinson's disease and healthy control fibroblasts

Abstract

Mitochondrial dysfunction has been proposed as one of the pathobiological underpinnings in Parkinson's disease. Environmental stressors, such as paraquat, induce mitochondrial dysfunction and promote reactive oxygen species production. Targeting oxidative stress pathways could prevent mitochondrial dysfunction and thereby halt the neurodegeneration in Parkinson's disease. Since curcumin is touted as an antioxidant and neuroprotective agent, the aim of this study was to investigate if curcumin is a suitable therapy to target mitochondrial dysfunction in Parkinson's disease using a paraquat-toxicity induced model in fibroblasts from LRRK2-mutation positive Parkinson's disease individuals and healthy controls. The fibroblasts were exposed to five treatment groups, (i) untreated, (ii) curcumin only, (iii) paraquat only, (iv) pre-curcumin group: with curcumin for 2hr followed by paraquat for 24hr and (v) post-curcumin group: with paraquat for 24hr followed by curcumin for 2hr. Mitochondrial function was determined by measuring three parameters of mitochondrial respiration (maximal respiration, ATP-associated respiration, and spare respiratory capacity) using the Seahorse XF^e96 Extracellular Flux Analyzer. As expected, paraquat effectively disrupted mitochondrial function for all parameters. Pre-curcumin treatment improved maximal and ATP-associated respiration whereas, post-curcumin treatment had no effect. These findings indicate that curcumin may be most beneficial as a pre-treatment before toxin exposure, which has implications for its therapeutic use. These promising findings warrant future studies testing different curcumin dosages, exposure times and curcumin formulations in larger sample sizes of Parkinson's disease and control participants.

Keywords: ATP, Adenosine Triphosphate; DMEM, Dulbecco's Modified Eagle Medium; DMSO, Dimethyl Sulfoxide; FCCP, Carbonyl cyanide-4-(trifluoromethoxy) phenylhydrazone; LRRK2, Leucine Rich Repeat Kinase 2; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; Mitochondrial function; OCR, oxygen consumption rate; Oxidative stress; PD, Parkinson's disease; Paraquat; Turmeric.

Fig. 1

Scatterplot profile of mitochondrial respiration parameters (pmol/min/AU) across five treatment groups in fibroblast cells derived from Parkinson's disease and control participants. The three respiration parameters evaluated were maximal (A–C), ATP-associated (D–F) and spare respiratory (G–I) respiration. The raw respiration values (4–6 technical replicates) are indicated by open circles for PD cases and closed circles for controls. The respiration parameters were compared between a mutation-positive PD case and their matched controls (PD case 1 with controls 1 and 2; PD case 2 with controls 3 and 4; PD case 3 with controls 5 and 6). ATP: Adenosine Triphosphate, OCR: oxygen consumption rate, PD: Parkinson's disease.