The field of small interfering RNA (siRNA) as potent sequence-

Neurotoxicity of human immunodeficiency virus-1 (HIV) includes synaptic simplification and neuronal apoptosis. However, the mechanisms of HIV-associated neurotoxicity remain unclear, thus precluding an effective treatment of the neurological complications. The present study was undertaken to characterize novel mechanisms of HIV neurotoxicity that may explain how HIV subjects develop neuronal degeneration. Several neurodegenerative disorders are characterized by mitochondrial dysfunction; therefore, we hypothesized that HIV promotes mitochondrial damage. We first analyzed brains from HIV encephalitis (HIVE) by electron microscopy. Several sections of HIVE subjects contained enlarged and damaged mitochondria compared to brains from HIV subjects with no neurological complications. Similar pathologies were observed in mice overexpressing the HIV protein gp120, suggesting that this viral protein may be responsible for mitochondrial pathology found in HIVE. To gain more information about the cellular mechanisms of gp120 neurotoxicity, we exposed rat cortical neurons to gp120 and we determined cellular oxygen consumption rate, mitochondrial distribution, and trafficking. Our data show that gp120 evokes impairment in mitochondrial function and distribution. These data suggest that one of the mechanisms of HIV neurotoxicity includes altered mitochondrial dynamics in neurons.

A number of human immunodeficiency virus type-1 (HIV) positive subjects are also opiate abusers. These individuals are at high risk to develop neurological complications. However, little is still known about the molecular mechanism(s) linking opiates and HIV neurotoxicity. To learn more, we exposed rat neuronal/glial cultures prepared from different brain areas to opiate agonists and HIV envelope glycoproteins gp120IIIB or BaL. These strains bind to CXCR4 and CCR5 chemokine receptors, respectively, and promote neuronal death. Morphine did not synergize the toxic effect of gp120IIIB but inhibited the cytotoxic property of gp120BaL. This effect was blocked by naloxone and reproduced by the μ opioid receptor agonist DAMGO. To examine the potential mechanism(s) of neuroprotection, we determined the effect of morphine on the release of chemokines CCL5 and CXCL12 in neurons, astrocytes and microglia cultures. CCL5 has been shown to prevent gp120BaL neurotoxicity while CXCL12 decreases neuronal survival. Morphine elicited a time-dependent release of CCL5 but failed to affect the release of CXCL12. This effect was observed only in primary cultures of astrocytes. To examine the role of endogenous CCL5 in the neuroprotective activity of morphine, mixed cerebellar neurons/glial cells were immunoneutralized against CCL5 prior to morphine and gp120 treatment. In these cells the neuroprotective effect of opiate agonists was blocked. Our data suggest that morphine may exhibit a neuroprotective activity against M-tropic gp120 through the release of CCL5 from astrocytes.

Three-prime repair exonuclease 1 knockout (Trex1 −/− ) mice suffer from systemic inflammation caused largely by chronic activation of the cyclic GMP-AMP synthase-stimulator of interferon genes-TANKbinding kinase-interferon regulatory factor 3 (cGAS-STING-TBK1-IRF3) signaling pathway. We showed previously that Trex1-deficient cells have reduced mammalian target of rapamycin complex 1 (mTORC1) activity, although the underlying mechanism is unclear. Here, we performed detailed metabolic analysis in Trex1 −/− mice and cells that revealed both cellular and systemic metabolic defects, including reduced mitochondrial respiration and increased glycolysis, energy expenditure, and fat metabolism. We also genetically separated the inflammatory and metabolic phenotypes by showing that Sting deficiency rescued both inflammatory and metabolic phenotypes, whereas Irf3 deficiency only rescued inflammation on the Trex1 −/− background, and many metabolic defects persist in Trex1 −/− Irf3 −/− cells and mice. We also showed that Leptin deficiency (ob/ob) increased lipogenesis and prolonged survival of Trex1 −/− mice without dampening inflammation. Mechanistically, we identified TBK1 as a key regulator of mTORC1 activity in Trex1 −/− cells. Together, our data demonstrate that chronic innate immune activation of TBK1 suppresses mTORC1 activity, leading to dysregulated cellular metabolism.M ammals have evolved complex and integrated systems of immunity and metabolism to maintain and defend internal and environmental threats. Increasing numbers of immune regulators have been found to play critical roles in metabolism. Studies from recent years have established an integrated view on the shared architecture between adaptive immunity and metabolism, including how they correspond to stimulus in disease settings. However, cell-intrinsic innate immune regulation of metabolic pathways remains poorly understood. This is in part due to the fact that overwhelming systemic inflammation in chronic diseases often masks direct underlying molecular causes.We have previously characterized an autoimmune/autoinflammatory disease mouse model, three-prime repair exonuclease 1 knockout (Trex1 −/− ) (1). TREX1, also known as DNase III, is an exonuclease that localizes to the endoplasmic reticulum (ER) to prevent aberrant accumulation of self-DNA or glycans that would trigger immune activation (2, 3). Mutations of the TREX1 gene have been associated with several autoinflammatory and autoimmune diseases, including Aicardi-Goutières syndrome and systemic lupus erythematosus (SLE) (4). Trex1 −/− mice suffer from systemic inflammation caused largely by chronic activation of the cytosolic DNA sensing pathway through the cyclic GMP-AMP synthase-stimulator of interferon genes-TANK-binding kinase-interferon regulatory factor 3 (cGAS-STING-TBK1-IRF3) cascade (5-7). We showed previously that TREX1 also regulates lysosomal biogenesis through the mTORC1-TFEB pathway and that Trex1 −/− mouse embryonic fibroblasts (MEFs) exhibit drastically reduced mTORC1 activity compare...

The hippocampus has a well-documented role for spatial navigation across species, but its role for spatial memory in nonnavigational tasks is uncertain. In particular, when monkeys are tested in tasks that do not require navigation, spatial memory seems unaffected by lesions of the hippocampus. However, the interpretation of these results is compromised by long-term compensatory adaptation occurring in the days and weeks after lesions. To test the hypothesis that hippocampus is necessary for nonnavigational spatial memory, we selected a technique that avoids long-term compensatory adaptation. We transiently disrupted hippocampal function acutely at the time of testing by microinfusion of the glutamate receptor antagonist kynurenate. Animals were tested on a self-ordered spatial memory task, the Hamilton Search Task. In the task, animals are presented with an array of eight boxes, each containing a food reinforcer; one box may be opened per trial, with trials separated by a delay. Only the spatial location of the boxes serves as a cue to solve the task. The optimal strategy is to open each box once without returning to previously visited locations. Transient inactivation of hippocampus reduced performance to chance levels in a delay-dependent manner. In contrast, no deficits were seen when boxes were marked with nonspatial cues (color). These results clearly document a role for hippocampus in nonnavigational spatial memory in macaques and demonstrate the efficacy of pharmacological inactivation of this structure in this species. Our data bring the role of the hippocampus in monkeys into alignment with the broader framework of hippocampal function.A lthough a role for the hippocampus in navigational spatial memory has been well documented in many species, including humans (1-4), rodents (5, 6), and monkeys (7-9), a role for hippocampus in nonnavigational spatial memory is less certain. Because nonhuman primates have a close neuroanatomical and behavioral homology to humans, they offer a unique opportunity to assess the neural substrates of spatial memory using nonnavigational tasks. However, studies using nonnavigational spatial tasks with nonhuman primates have found little or no effect of hippocampal lesions (10-15).The ability of hippocampal-lesioned monkeys to perform these tasks without impairment has been explained by the reliance on a strategy that is not dependent on hippocampus. Whereas the use of allocentric (world-centered) cues depends on the hippocampus, it is thought that the use of egocentric (body-centered) cues does not. Indeed, it has been suggested that the use of egocentric cues is supported by extrahippocampal substrates including striatum and parietal cortex (15)(16)(17)(18).Following a hippocampal lesion, subjects may learn to resolve a given task by developing a strategy distinct from that used in the presence of an intact hippocampus. Several factors may support this compensatory strategy, including (i) postlesion training or retraining and (ii) postlesion network reorganization (19-21). T...