Cellular senescence in honey bee brain is largely independent of chronological age

Abstract

Accumulation of oxidative stress-induced damage in brain tissue plays an important role in the pathogenesis of normal aging and neurodegenerative diseases. Neuronal oxidative damage typically increases with age in humans, and also in the invertebrate and vertebrate model species most commonly used in aging research. By use of quantitative immunohistochemistry and Western blot, we show that this aspect of brain senescence is largely decoupled from chronological age in the honey bee (Apis mellifera). The bee is a eusocial insect characterized by the presence of a reproductive queen caste and a caste of functionally sterile female workers that performs various alloparental tasks such as nursing and foraging. We studied patterns of oxidative nitration and carbonylation damage in the brain of worker bees that performed nurse tasks as 8-and 200-day-olds and foraging tasks as 20-and 200-day-olds. In addition, we examined 180-day-old diutinus bees, a stress-resistant temporal worker form that survives unfavorable periods. Our results indicate that nitration damage occurs only at low levels in vivo, but that a 60-kDa protein from honey bee brain is selectively nitrated by peroxynitrite in vitro. Oxidative carbonylation is present at varying levels in the visual and chemosensory neuropiles of worker bees, and this inter-individual variation is better explained by social role than by chronological age.

Mortality rates of honey bees in the wild

“…Thus one would expect senescence to commence with the switch from nurse bees to foragers because the force of natural selection would start declining rapidly with forager age (Kirkwood and Austad, 2000). Indeed oxidative stress-induced damage in the honey bee brain occurs in foragers but not hive bees regardless of chronological age (Seehuus et al, 2006). Forager bumblebees (Bombus terrestris) also exhibit reduced immunocompetence compared to hive workers of similar ages (Konig and Schmid-Hempel, 1995) suggesting differential effects of senescence on foragers and hive bees.…”

“…The literature on honey bee senescence is somewhat inconclusive. Laboratory data indicate cellular senescence in honey bees (Seehuus et al, 2006) and Remolina et al (2007) documented lower resistance to starvation in older honey bees, which indicates effects of senescence. Rueppell et al (2007b) documented increased mortality rates with age in bees collected from an outdoors hive and maintained in indoor cages until death.…”

The use of honeybees reared in a thermostatic chamber for aging studies

“…Although honeybees are a suitable model for aging studies, it is argued that the aging level of worker honeybees in the field hive is not certain because the aging level was claimed to depend on chronological age and task performance (Neukirch 1982;Rueppell et al 2007a), or to be decoupled from chronological age (Seehuus et al 2006a;Rueppell et al 2007b). In order to eliminate the problem of task performance and confirm the relationship between chronological age and aging, in this study, we reared newly emerged workers in a thermostat at 34°C throughout their lives.…”

Lifespan behavioural and neural resilience in a social insect

“…We are thus confident that we could detect effects of relevant size in all assays. All power analyses were conducted in PASS 14 (NCSS Statistical Software, Kaysville, UT, USA).…”

“…Ageing nervous systems may functionally decline, leading to sensory and motor deficits [6,7] due to neurodegeneration, manifest as apoptosis ( programmed cell death), which may increase with age [8], disease [9] or development [10]. Few studies have examined the influence of sociality on ageing and life history [11][12][13], and little is understood about cognitive decline and neurobiological changes accompanying senescence in social animals, apart from humans [12,[14][15][16]. Social insects have striking lifespan polyphenisms [17][18][19][20]: queens often live more than a decade, whereas workers may live only several months [21], indicating that the differentiation of reproductive and sterile castes has had profound effects on senescence, which may be influenced by the social organization of colony labour.…”