Circadian Rhythms of Oxidative Phosphorylation: Effects of Rotenone and Melatonin on Isolated Rat Brain Mitochondria

Abstract

Mitochondrial experiments are of increasing interest in different fields of research. Inhibition of mitochondrian activities seems to play a role in Parkinson's disease and in this regard several animal models have used inhibitors of mitochondrial respiration such as rotenone or MPTP. Most of these experiments were done during the daytime. However, there is no reason for mitochondrial respiration to be constant during the 24 h. This study investigated the circadian variation of oxidative phosphorylation in isolated rat brain mitochondria and the administration-time-dependent effect of rotenone and melatonin. The respiratory control ratio, state 3 and state 4, displayed a circadian fluctuation. The highest respiratory control ratio value (3.01) occurred at 04:00 h, and the lowest value (2.63) at 08:00 h. The highest value of state 3 and state 4 oxidative respiration occurred at 12:00 h and the lowest one at 20:00 h. The 24 h mean decrease in the respiratory control ratio following incubation with melatonin and rotenone was 7 and 32%, respectively; however, the exact amount of the inhibition exerted by these agents varied according to the time of the mitochondria isolation. Our results show the time of mitochondrial isolation could lead to interindividual variability. When studies require mitochondrial isolation from several animals, the time between animal experiments has to be minimized. In oxidative phosphorylation studies, the time of mitochondria isolation must be taken into account, or at least specified in the methods section.

Melatonin and mitochondrial function

“…Studies performed in rats reveal that OXPHOS displays a circadian rhythm (Simon et al, 2003), possibly regulated by the daily fluctuations in melatonin, although further experiments are necessary to confirm this point. Melatonin is known to inhibit mitochondrial gene expression in isolated brown adipocyes obtained from Syrian hamsters (Prunet-Marcassus et al, 2001).…”

Melatonin Inhibits Benzene-Induced Lipid Peroxidation in Rat Liver

“…Melatonin increases the activity of the respiratory chain complexes I and IV, inhibits mitochondrial pathways of apoptosis, and participates in the circadian oscillations of oxidative phosphorylation (46,47). Metabolic pathways of melatonin in microsomes and mitochondria involve the same CYPs.…”

Melatonin as a Neuroprotective Agent in the Rodent Models of Parkinson’s Disease: Is it All Set to Irrefutable Clinical Translation?

“…However, variations may arise because of the time points considered for the isolation and fractionation of the nigrostriatal tissues and mitochondrial preparations under various experimental paradigms. Variations in the results across studies could be maximally minimized when the time of the isolation of tissues and mitochondrial fraction may be taken into account [58].…”