Inhalation of marijuana affects Drosophila heart function

Abstract

We investigated the effect of inhalation of vaporized marijuana on cardiac function in Drosophila melanogaster, a suitable genetic model for studying human diseases. Adult flies were exposed to marijuana for variable time periods and the effects on cardiac function were studied. Short treatment protocol incremented heart-rate variability. Contractility was augmented only under prolonged exposure to cannabis and it was associated with incremented calcium transient within cardiomyocytes. Neither the activity of the major proteins responsible for calcium handling nor the calcium load of the sarcoplasmic reticulum were affected by the cannabis treatment. The observed changes manifested in the cardiomyocytes even in the absence of the canonical cannabinoid receptors described in mammals. Our results are the first evidence of the in vivo impact of phytocannabinoids in D. melanogaster. By providing a simple and affordable platform prior to mammalian models, this characterization of cardiac function under marijuana exposure opens new paths for conducting genetic screenings using vaporized compounds.This article has an associated First Person interview with the first author of the paper.

Keywords: Cannabis; CBD; Calcium; Cardiac; Drosophila; THC.

Fig. 1.

Chronic exposure of D. melanogaster to vaporized herbal Cannabis sp. does not affect lifespan. (A) Device connected to a vaporizer designed for providing air or marijuana into a vial containing flies. (B) Representation of the lifespan percentage of flies under treatment. (C) Mortality of treated (green) and non-treated (red) adult flies was represented throughout the life of two synchronized populations of adult flies that emerged from puparium. Air: N=196, treated: N=170. Statistical comparison and curves were obtained using the Kaplan–Meier method and analyzed using the log-rank (Mantel-Cox) test.

Fig. 2.

Cardiac performance is modified by Cannabis sp. Flies harboring the reporter system handC-GFP (handC-GFP/+) were analyzed. (A) Typical recordings (top) and digitalized signals (bottom) of heart wall displacements for each group during 5 s. (B–D) Average results (±s.e.m.). (B) Arrhythmicity index is incremented during short-term exposure to marijuana. (C) Contractility is significantly incremented in flies treated with marijuana for 11–13 days. (D) Heart rate remains unchanged. N = air 6–8 days (17), marijuana 6–8 days (10), air 11–13 days (7), marijuana 11–13 days (11). One-way analysis of variance (ANOVA) followed by Tukey's post hoc test. *P<0.05, **P<0.01.

Fig. 3.

Cannabis increments Ca²⁺ transient amplitude but does not modify SR calcium load, fractional release, SERCA and NCX activity in the Drosophila heart. Ten-day-old flies harboring the reporter system GCaMP3 (genotype: UAS-GCaMP3/+; tinCΔ4-Gal4, UAS-GCaMP3/+) were exposed to air or marijuana. (A) Image and representative tracing of Ca²⁺ transient. A pulse of 10 mM caffeine is applied to the semi-intact preparation and visualized as a sudden increase in the fluorescence signal. (B–F) Average results (±s.e.m.). (B) Amplitude of Ca²⁺ transient [N = air (15), marijuana (10)]. (C) SR Ca²⁺ content [N = air (9), marijuana (6)]. (D) Fractional release [N = air (11), marijuana (7)]. (E) SERCA activity [N = air (12), marijuana (8)]. (F) NCX activity [N = air (12), marijuana (8)]. Student's t-test (two-tailed) was utilized for comparison between two groups. *P<0.05.