Glial Hsp70 Protects K+ Homeostasis in the Drosophila Brain during Repetitive Anoxic Depolarization

Neural tissue is particularly vulnerable to metabolic stress and loss of ion homeostasis. Repetitive stress generally leads to more permanent dysfunction but the mechanisms underlying this progression are poorly understood. We investigated the effects of energetic compromise in Drosophila by targeting the Na+/K+-ATPase. Acute ouabain treatment of intact flies resulted in subsequent repetitive comas that led to death and were associated with transient loss of K+ homeostasis in the brain. Heat shock pre-conditioned flies were resistant to ouabain treatment. To control the timing of repeated loss of ion homeostasis we subjected flies to repetitive anoxia while recording extracellular [K+] in the brain. We show that targeted expression of the chaperone protein Hsp70 in glial cells delays a permanent loss of ion homeostasis associated with repetitive anoxic stress and suggest that this is a useful model for investigating molecular mechanisms of neuroprotection

Genome-Wide Patterns of Gene Expression during Aging in the African Malaria Vector Anopheles gambiae

The primary means of reducing malaria transmission is through reduction in longevity in days of the adult female stage of the Anopheles vector. However, assessing chronological age is limited to crude physiologic methods which categorize the females binomially as either very young (nulliparous) or not very young (parous). Yet the epidemiologically relevant reduction in life span falls within the latter category. Age-grading methods that delineate chronological age, using accurate molecular surrogates based upon gene expression profiles, will allow quantification of the longevity-reducing effects of vector control tools aimed at the adult, female mosquito. In this study, microarray analyses of gene expression profiles in the African malaria vector Anopheles gambiae were conducted during natural senescence of females in laboratory conditions. Results showed that detoxification-related and stress-responsive genes were up-regulated as mosquitoes aged. A total of 276 transcripts had age-dependent expression, independently of blood feeding and egg laying events. Expression of 112 (40.6%) of these transcripts increased or decreased monotonically with increasing chronologic age. Seven candidate genes for practical age assessment were tested by quantitative gene amplification in the An. gambiae G3 strain in a laboratory experiment and the Mbita strain in field enclosures set up in western Kenya under conditions closely resembling natural ones. Results were similar between experiments, indicating that senescence is marked by changes in gene expression and that chronological age can be gauged accurately and repeatedly with this method. These results indicate that the method may be suitable for accurate gauging of the age in days of field-caught, female An. gambiae

Differential patterns of apoptosis in response to aging in Drosophila

Several lines of evidence suggest that programmed cell death may play a role in the aging process and the age-related functional declines of multicellular organisms. To pave the way for the use of Drosophila to rigorously test this hypothesis in a genetic model organism, this work examines the pattern of apoptosis in the adult fly during aging. The analysis across the lifespan of caspase activity and DNA fragmentation shows that apoptosis occurs in adult flies at all ages and that it is linked to physiological age. The results establish that under normal conditions, fly aging is coupled with a lifelong gradual increase of apoptosis within muscle cells and an activation of apoptosis in fat cells of old flies. The nervous system does not show signs of apoptosis. These time- and tissue-specific changes indicate that aging influences the levels and the nature of the cells that commit to apoptosis. The comparison with the apoptotic response to starvation and oxidative stresses strongly suggests that the lifelong increase in flight and leg muscles results from the accumulation of oxidative damage associated with aging. This finding presents an attractive mechanism to account for the decline of locomotor functions and muscle loss in the elderly and opens the way for the genetic analysis of sarcopenia in Drosophila