Reserpine requires the D2-type receptor, dop-3, and the exoribonuclease, eri-1, to extend the lifespan in C. elegans.

Lifespan extension is an all systems encompassing event. Involvement of reduced insulin/IGF1 signalling is well worked out, first in the model organism Caenorhbaditis elegans followed by other systems including humans. But the role of neuronal component in lifespan extension is not well understood due to the refractory nature of neurons to small RNA interference (sRNAi) in C. elegans. Earlier, we have demonstrated that an antihypertensive drug, reserpine, extends lifespan through modulation of neurotransmitter release, especially, acetylcholine, in C. elegans. Intriguingly, the reserpine mediated lifespan extension (RMLE) does not happen through the known longevity pathways. Here, we report that the D2-type dopamine receptor (DOP-3), which acts through the inhibitory Gprotein coupled (G alpha i) pathway mediated signalling is partly required for RMLE. In the dop-3 loss of function mutant RMLE is shortened. DOP-3 acts through Gαo (goa-1). One of the downstream targets of G protein signalling is the transcription factor, jun-1. MRP-1, an ATP binding cassette transporter, belonging to the multidrug resistance protein family is one of the genes turned on by JUN-1. RMLE is shortened in dop-3-->goa-1-->jun1-->mrp-1 loss of function mutants, elucidating the contribution of dop-3 signalling. The dop-3 receptor system is known to inhibit acetylcholine release. This suggests dopamine receptor, dop-3 could be contributing to the modulation of acetylcholine release by reserpine. ERI-1 is a 3'-5' exoribonuclease, one of the negative regulators of sRNAi, whose loss of function makes neurons amenable to siRNA. In the absence of eri-1, RMLE is shortened. In the dop-3 loss-of-function background, lack of eri-1 completely abolishes RMLE. This suggests that dop-3 and eri-1 act in independent parallel pathways for RMLE and these two pathways are essential and sufficient for the longevity enhancement by reserpine in C. elegans.

A Novel Way of Amelioration of Amyloid Beta Induced Toxicity in Caenorhabditis elegans.

BACKGROUND: With an incidence of 1 in 85 persons above the age of 60 years succumbing to the disease, Alzheimer's disease (AD), has been predicted to create havoc globally. In spite of enormous efforts and exhaustive research, no cure is in sight. Hence, it is critical to unravel the mechanism of AD development/protection and identification of a cure soon. PURPOSE: This study is aimed at investigating the mechanism of reserpine action, which alleviates the toxicity of amyloid beta (Aß) (AD-causing peptide) in Caenorhabditis elegans [1, 2]. METHODS: Determination of alleviation of Aß toxicity with reserpine manifested as reduction in progressive paralysis, in the background of GFP reporter driven by the promoter of the FMRFamide neuropeptide, FLP-11 (AD; Pflp-11::GFP) and acetylcholine contribution through aldicarb (which inhibits acetylcholine esterase) treatment. RESULTS: The most significant protection against Aß toxicity was obtained in the background of Pflp-11::GFP. This protection had 2 components. The promoter of FLP-11 with the reporter GFP, Pflp-11::GFP, per se gave significant protection. Further reserpine treatment provided additional alleviation. Together they could almost eliminate Aß toxicity. These 2 components of Aß toxicity alleviation are dependent on acetylcholine levels, as an increase in acetylcholine by aldicarb treatment reduces the protective effect. CONCLUSION: A unique way to alleviate Aß toxicity is reserpine treatment in combination with Pflp-11::GFP. Reserpine should be evaluated as a potential drug in a pilot study in AD patients. Furthermore, identification of the mechanism of Pflp-11::GFP-mediated reduction in Aß toxicity is a potential pathway to develop therapeutics for AD.