HALOPERIDOL

Our first project within SWIRL was examining the effects of 2,4-dinitrophenol (DNP) on Lumbriculus variegatus and the effects of haloperidol on reversing toxicity observed following DNP exposure. 

The work is summarised in the below abstract: 

Investigating haloperidol as an antidote for 2,4-dinitrophenol using a novel in vivo model, Lumbriculus variegatus

Caitlin Bellamy, Dr Aidan Seeley, Dr Nia A. Davies, Prof. Melisa J. Wallace 

Introduction

2,4-dinitrophenol (DNP) is a toxic uncoupler of oxidative phosphorylation causing hyperthermia and other lethal effects which is being used as a weight-loss supplement. [1] In vitro studies suggest that haloperidol forms an acid-base complex with DNP [2] which may reduce toxicity. Here we use a novel in vivo model, Lumbriculus variegatus, to determine the effects of haloperidol on DNP-induced toxicity. 

Method

L. variegatus display two stereotypical behaviours in response to tactile stimulation: body reversal and helical swimming. L. variegatus ability to perform these movements before and after exposure to haloperidol, DNP, and in combination was scored. Stereotypical movements were recorded before drug exposure, after a 10 min exposure to DNP (0.5-50 µM), or haloperidol (1-100 µM), and a 10 min and 24 hr rescue period. We also used the free locomotion assay which utilises rapid image collection to measure unstimulated movement of L. variegatus under the same conditions. Statistical significance was determined by a non-parametric paired t-test or a two-way ANOVA. 

Results

DNP significantly inhibited body reversal (P=.0156, n=8) and helical swimming (P=.015, n=8) at concentrations as low as 5 µM, while 12.5 µM DNP was shown to have inhibitory effects up to 24 hr post-exposure (P=.008, n=8). Haloperidol alone showed no observable adverse effects up to 25 µM (P>.05, n=7). L. variegatus ability to perform stereotypical movements was then measured after exposure to DNP followed by 25 µM of haloperidol. Treatment with haloperidol rescued DNP-mediated behavioural inhibition such that stereotypical movement measures returned to baseline levels (P>.05, n=8). 

Free locomotion was unaffected by haloperidol alone at concentrations up to 25 µM (P>.05, n=6). However, 24 hr after DNP exposure, free locomotion was inhibited up to 95.40±1.60% when exposed to DNP alone (P=<.0001, n=6). When haloperidol was administered after DNP exposure, behaviours observed 24 hr after DNP administration were similar to pre-exposure levels (P>.05, n=6).

Conclusion

This work highlights the utility of L. variegatus for pharmacology and toxicology testing and the use of L. variegatus as an in vivo model for studying the underlying mechanism for haloperidol to reverse the toxic effects of DNP. 

References

1. Goldgof et al. The Chemical Uncoupler 2,4-Dinitrophenol (DNP) Protects against Diet-induced Obesity and Improves Energy Homeostasis in Mice at Thermoneutrality. J Bio Chem. 2014;289(28):19341-19350. 

2. Plater & Harrison. The complexation of 2,4-dinitrophenol with basic drugs: Acid + base = salt. J Chem Res. 2019;43(7-8):281-286.