Antioxidant N-acetyl-L-cysteine ameliorates symptoms of premature aging associated with the deficiency of the circadian protein BMAL1

Abstract

Deficiency of the circadian clock protein BMAL1 leads to premature aging and increased levels of reactivate oxygen species in several tissues of mice. In order to investigate the role of oxidative stress in accelerated aging and development of age-related pathologies, we continuously administered the antioxidant N-acetyl-L-cysteine toBmal1-deficient mice through their entire lifespan by supplementing drinking water. We found that the life long treatment with antioxidant significantly increased average and maximal lifespan and reduced the rate of age-dependent weight loss and development of cataracts. At the same time, it had no effect on time of onset and severity of other age-related pathologies characteristic of Bmal1-/- mice, such as joint ossification, reduced hair regrowth and sarcopenia. We conclude that chronic oxidative stress affects longevity and contributes to the development of at least some age-associated pathology, although ROS-independent mechanisms may also play a role. Our bioinformatics analysis identified the presence of a conservative E box element in the promoter regions of several genes encoding major antioxidant enzymes. We speculate that BMAL1 controls antioxidant defense by regulating the expression of major antioxidant enzymes.

Keywords: BMAL1; aging; circadian clock; oxidative stress.

Figure 1.. Continuous administration of NAC affects age-dependent changes in body weight.

Total body weight of male (A) WT and (B) Bmal1-/- mice, closed circles - control mice raised on regular water; open circles - mice raised on water supplemented with 40mM of NAC. (C) Relative water consumption by WT mice receiving either regular (closed bar) or NAC-supplemented (open bar) water. (D) Age-dependent changes in relative body weight in Bmal1-/- mice measured at each time point as the percentage of the body weight of WT mice of the same group.

Figure 2.. Effects of continuous administration of NAC on development of eye pathology and muscle strength.

(A) Frequency of cataracts in 30-week old and 45-week old Bmal1-/- mice raised on regular (closed bars) or NAC-supplemented (open bars) water. Each eye was counted independently; the percentage of cataracts was determined by dividing the number of cataracts by the total number of eyes, if an animal was dead at the time of observation, then the previous score for this animal was used. (B) Age-dependent changes in muscular strength of WT (green bars) and Bmal1-/- mice receiving regular (black bars) or NAC-supplemented (red bars) water. Muscular strength was evaluated as the ability of animals of indicated age to maintain their weight on the inverted grid. Each animal was tested five times, if the animal did not fall down for 30 sec the trial was counted as successful. The percentage of successful trials was calculated and plotted. No difference was detected between NAC-treated and control Bmal1-/- animals.

Figure 3.. Continuous administration of NAC increases lifespan of Bmal1-/- mice.

Kaplan-Meyer survival curves were obtained for WT mice raised on regular (closed circles) or NAC-supplemented (open circles) water; and Bmal1-/- mice raised on regular (closed triangles) or NAC-supplemented (open triangles) water. NAC significantly increased lifespan of Bmal1-/- mice (P =0.022, log-rank Mantel-Haenszel test).