Person:

Campbell, Jennifer

Numerous longevity genes have been discovered in model organisms and altering their function results in prolonged lifespan. In mammals, some have speculated that any health benefits derived from manipulating these same pathways might be offset by increased cancer risk on account of their propensity to boost cell survival. The Sir2/SIRT1 family of NAD+-dependent deacetylases is proposed to underlie the health benefits of calorie restriction (CR), a diet that broadly suppresses cancer in mammals. Here we show that CR induces a two-fold increase SIRT1 expression in the intestine of rodents and that ectopic induction of SIRT1 in a β-catenin-driven mouse model of colon cancer significantly reduces tumor formation, proliferation, and animal morbidity in the absence of CR. We show that SIRT1 deacetylates β-catenin and suppresses its ability to activate transcription and drive cell proliferation. Moreover, SIRT1 promotes cytoplasmic localization of the otherwise nuclear-localized oncogenic form of β-catenin. Consistent with this, a significant inverse correlation was found between the presence of nuclear SIRT1 and the oncogenic form of β−catenin in 81 human colon tumor specimens analyzed. Taken together, these observations show that SIRT1 suppresses intestinal tumor formation in vivo and raise the prospect that therapies targeting SIRT1 may be of clinical use in β−catenin-driven malignancies.

Background: Despite the advent of highly active anti-retroviral therapy (HAART), HIV-associated neurocognitive disorders continue to be a significant problem. In efforts to understand and alleviate neurocognitive deficits associated with HIV, we used an accelerated simian immunodeficiency virus (SIV) macaque model of NeuroAIDS to test whether minocycline is neuroprotective against lentiviral-induced neuronal injury. Methodology/Principal Findings: Eleven rhesus macaques were infected with SIV, depleted of CD8+ lymphocytes, and studied until eight weeks post inoculation (wpi). Seven animals received daily minocycline orally beginning at 4 wpi. Neuronal integrity was monitored in vivo by proton magnetic resonance spectroscopy and post-mortem by immunohistochemistry for synaptophysin (SYN), microtubule-associated protein 2 (MAP2), and neuronal counts. Astrogliosis and microglial activation were quantified by measuring glial fibrillary acidic protein (GFAP) and ionized calcium binding adaptor molecule 1 (IBA-1), respectively. SIV infection followed by CD8+ cell depletion induced a progressive decline in neuronal integrity evidenced by declining N-acetylaspartate/creatine (NAA/Cr), which was arrested with minocycline treatment. The recovery of this ratio was due to increases in NAA, indicating neuronal recovery, and decreases in Cr, likely reflecting downregulation of glial cell activation. SYN, MAP2, and neuronal counts were found to be higher in minocycline-treated animals compared to untreated animals while GFAP and IBA-1 expression were decreased compared to controls. CSF and plasma viral loads were lower in MN-treated animals. Conclusions/Significance: In conclusion, oral minocycline alleviates neuronal damage induced by the AIDS virus.