Reducing acetylated tau is neuroprotective in brain injury

Traumatic brain injury (TBI) is the largest non-genetic, non-aging related risk factor for Alzheimer's disease (AD). We report here that TBI induces tau acetylation (ac-tau) at sites acetylated also in human AD brain. This is mediated by S-nitrosylated-GAPDH, which simultaneously inactivates Sirtuin1 deacetylase and activates p300/CBP acetyltransferase, increasing neuronal ac-tau. Subsequent tau mislocalization causes neurodegeneration and neurobehavioral impairment, and ac-tau accumulates in the blood. Blocking GAPDH S-nitrosylation, inhibiting p300/CBP, or stimulating Sirtuin1 all protect mice from neurodegeneration, neurobehavioral impairment, and blood and brain accumulation of ac-tau after TBI. Ac-tau is thus a therapeutic target and potential blood biomarker of TBI that may represent pathologic convergence between TBI and AD. Increased ac-tau in human AD brain is further augmented in AD patients with history of TBI, and patients receiving the p300/CBP inhibitors salsalate or diflunisal exhibit decreased incidence of AD and clinically diagnosed TBI.

(-)-P7C3-S243 Protects a Rat Model of Alzheimer's Disease From Neuropsychiatric Deficits and Neurodegeneration Without Altering Amyloid Deposition or Reactive Glia

BACKGROUND

In addition to cognitive deficits, Alzheimer's disease (AD) is associated with other neuropsychiatric symptoms, including severe depression. Indeed, depression often precedes cognitive deficits in patients with AD. Unfortunately, the field has seen only minimal therapeutic advances, underscoring the critical need for new treatments. P7C3 aminopropyl carbazoles promote neuronal survival by enhancing nicotinamide adenine dinucleotide flux in injured neurons. Neuroprotection with P7C3 compounds has been demonstrated in preclinical models of neurodegeneration by virtue of promoting neuronal survival independently of early disease-specific pathology, resulting in protection from cognitive deficits and depressive-like behavior. We hypothesize that P7C3 compounds might be uniquely applicable to patients with AD, given the comorbid presentation of depression and cognitive deficits.

METHODS

Aging male and female wild-type and TgF344-AD rats, a well-characterized preclinical AD model, were administered (-)-P7C3-S243 daily for 9 and 18 months, beginning at 6 months of age. Behavioral phenotypes related to cognition and depression were assessed at 15 and 24 months, and brain pathology and biochemistry were assessed at 24 months.

RESULTS

(-)-P7C3-S243 safely protected aging male and female wild-type and TgF344-AD rats from cognitive deficits and depressive-like behavior. Depressive-like behavior occurred earlier than cognitive deficits in TgF344-AD rats, consistent with AD in many patients. Treatment with (-)-P7C3-S243 blocked neurodegeneration in TgF344-AD rats, without altering amyloid deposition or indicators of neuroinflammation.

CONCLUSIONS

Neuronal cell death-specific treatment approaches, such as P7C3 compounds, may represent a new treatment approach for patients experiencing the combination of cognitive deficits and depression associated with AD.

Neuroprotective Efficacy of a Sigma 2 Receptor/TMEM97 Modulator (DKR-1677) after Traumatic Brain Injury

Compounds targeting the sigma 2 receptor, which we recently cloned and showed to be identical with transmembrane protein 97 (σ2R/TMEM97), are broadly applicable therapeutic agents currently in clinical trials for imaging in breast cancer and for treatment of Alzheimer's disease and schizophrenia. These promising applications coupled with our previous observation that the σ2R/TMEM97 modulator SAS-0132 has neuroprotective attributes and improves cognition in wild-type mice suggests that modulating σ2R/TMEM97 may also have therapeutic benefits in other neurodegenerative conditions such as traumatic brain injury (TBI). Herein, we report that DKR-1677, a novel derivative of SAS-0132 with increased affinity and selectivity for σ2R/Tmem97 ( K_i = 5.1 nM), is neuroprotective after blast-induced and controlled cortical impact (CCI) TBI in mice. Specifically, we discovered that treatment with DKR-1677 decreases axonal degeneration after blast-induced TBI and enhances survival of cortical neurons and oligodendrocytes after CCI injury. Furthermore, treatment with DKR-1677 preserves cognition in the Morris water maze after blast TBI. Our results support an increasingly broad role for σ2R/Tmem97 modulation in neuroprotection and suggest a new approach for treating patients suffering from TBI.

Neuroprotective efficacy of P7C3 compounds in primate hippocampus

There is a critical need for translating basic science discoveries into new therapeutics for patients suffering from difficult to treat neuropsychiatric and neurodegenerative conditions. Previously, a target-agnostic in vivo screen in mice identified P7C3 aminopropyl carbazole as capable of enhancing the net magnitude of postnatal neurogenesis by protecting young neurons from death. Subsequently, neuroprotective efficacy of P7C3 compounds in a broad spectrum of preclinical rodent models has also been observed. An important next step in translating this work to patients is to determine whether P7C3 compounds exhibit similar efficacy in primates. Adult male rhesus monkeys received daily oral P7C3-A20 or vehicle for 38 weeks. During weeks 2-11, monkeys received weekly injection of 5'-bromo-2-deoxyuridine (BrdU) to label newborn cells, the majority of which would normally die over the following 27 weeks. BrdU+ cells were quantified using unbiased stereology. Separately in mice, the proneurogenic efficacy of P7C3-A20 was compared to that of NSI-189, a proneurogenic drug currently in clinical trials for patients with major depression. Orally-administered P7C3-A20 provided sustained plasma exposure, was well-tolerated, and elevated the survival of hippocampal BrdU+ cells in nonhuman primates without adverse central or peripheral tissue effects. In mice, NSI-189 was shown to be pro-proliferative, and P7C3-A20 elevated the net magnitude of hippocampal neurogenesis to a greater degree than NSI-189 through its distinct mechanism of promoting neuronal survival. This pilot study provides evidence that P7C3-A20 safely protects neurons in nonhuman primates, suggesting that the neuroprotective efficacy of P7C3 compounds is likely to translate to humans as well.

Treatment with Uric Acid Reduces Infarct and Improves Neurologic Function in Female Mice After Transient Cerebral Ischemia

BACKGROUND

Exogenous administration of uric acid, a naturally occurring antioxidant that scavenges reactive oxygen species in vasculature, has shown protective efficacy in both rodent models of stroke and human stroke patients in Spain as an adjuvant treatment to mechanical thrombectomy. Before clinical trials can be initiated in the United States, however, confirmation of efficacy in alternative preclinical models is required in accordance with stroke therapy academic industry roundtable-RIGOR criteria. To date, preclinical efficacy has only been established in the acute setting in male rodents.

METHODS

To address this need, we subjected 7- to 9-week old ovariectomized female mice to filament-induced right middle cerebral artery ischemia and reperfusion, an established preclinical model of mechanical thrombectomy. Fidelity of the procedure was monitored by laser Doppler flowmetry. A separate lab randomly assigned animals to vehicle versus uric acid infusion, which was initiated immediately after 45 minutes of reperfusion. Poststroke analysis of infarction size and neurologic function were conducted by investigators blind to treatment group, with a 7-day primary endpoint and a 3-day intermediary analysis at 1and.

RESULTS

Infarct size and neurologic function at 7 days poststroke were significantly improved in uric acid-treated animals, relative to vehicle.

CONCLUSION

Efficacy of uric acid in preclinical models of stroke is now expanded to include female mice analyzed at a later time point than has been investigated previously. These results support stroke therapy academic industry roundtable-RIGOR driven determination of the suitability of acute administration of uric acid as an adjuvant to mechanical thrombectomy in clinical trials for patients with stroke.

Maternal P7C3-A20 Treatment Protects Offspring from Neuropsychiatric Sequelae of Prenatal Stress

Aims: Impaired embryonic cortical interneuron development from prenatal stress is linked to adult neuropsychiatric impairment, stemming in part from excessive generation of reactive oxygen species in the developing embryo. Unfortunately, there are no preventive medicines that mitigate the risk of prenatal stress to the embryo, as the underlying pathophysiologic mechanisms are poorly understood. Our goal was to interrogate the molecular basis of prenatal stress-mediated damage to the embryonic brain to identify a neuroprotective strategy. Results: Chronic prenatal stress in mice dysregulated nicotinamide adenine dinucleotide (NAD⁺) synthesis enzymes and cortical interneuron development in the embryonic brain, leading to axonal degeneration in the hippocampus, cognitive deficits, and depression-like behavior in adulthood. Offspring were protected from these deleterious effects by concurrent maternal administration of the NAD⁺-modulating agent P7C3-A20, which crossed the placenta to access the embryonic brain. Prenatal stress also produced axonal degeneration in the adult corpus callosum, which was not prevented by maternal P7C3-A20. Innovation: Prenatal stress dysregulates gene expression of NAD⁺-synthesis machinery and GABAergic interneuron development in the embryonic brain, which is associated with adult cognitive impairment and depression-like behavior. We establish a maternally directed treatment that protects offspring from these effects of prenatal stress. Conclusion: NAD⁺-synthesis machinery and GABAergic interneuron development are critical to proper embryonic brain development underlying postnatal neuropsychiatric functioning, and these systems are highly susceptible to prenatal stress. Pharmacologic stabilization of NAD⁺ in the stressed embryonic brain may provide a neuroprotective strategy that preserves normal embryonic development and protects offspring from neuropsychiatric impairment. Antioxid. Redox Signal. 35, 511-530.

Ca2+-Binding Protein 1 Regulates Hippocampal-dependent Memory and Synaptic Plasticity

Ca²⁺-binding protein 1 (CaBP1) is a Ca²⁺-sensing protein similar to calmodulin that potently regulates voltage-gated Ca²⁺ channels. Unlike calmodulin, however, CaBP1 is mainly expressed in neuronal cell-types and enriched in the hippocampus, where its function is unknown. Here, we investigated the role of CaBP1 in hippocampal-dependent behaviors using mice lacking expression of CaBP1 (C-KO). By western blot, the largest CaBP1 splice variant, caldendrin, was detected in hippocampal lysates from wild-type (WT) but not C-KO mice. Compared to WT mice, C-KO mice exhibited mild deficits in spatial learning and memory in both the Barnes maze and in Morris water maze reversal learning. In contextual but not cued fear-conditioning assays, C-KO mice showed greater freezing responses than WT mice. In addition, the number of adult-born neurons in the hippocampus of C-KO mice was ∼40% of that in WT mice, as measured by bromodeoxyuridine labeling. Moreover, hippocampal long-term potentiation was significantly reduced in C-KO mice. We conclude that CaBP1 is required for cellular mechanisms underlying optimal encoding of hippocampal-dependent spatial and fear-related memories.

Characterization of the Jet-Flow Overpressure Model of Traumatic Brain Injury in Mice

The jet-flow overpressure chamber (OPC) has been previously reported as a model of blast-mediated traumatic brain injury (bTBI). However, rigorous characterization of the features of this injury apparatus shows that it fails to recapitulate exposure to an isolated blast wave. Through combined experimental and computational modeling analysis of gas-dynamic flow conditions, we show here that the jet-flow OPC produces a collimated high-speed jet flow with extreme dynamic pressure that delivers a severe compressive impulse. Variable rupture dynamics of the diaphragm through which the jet flow originates also generate a weak and infrequent shock front. In addition, there is a component of acceleration-deceleration injury to the head as it is agitated in the headrest. Although not a faithful model of free-field blast exposure, the jet-flow OPC produces a complex multi-modal model of TBI that can be useful in laboratory investigation of putative TBI therapies and fundamental neurophysiological processes after brain injury.

Acutely blocking excessive mitochondrial fission prevents chronic neurodegeneration after traumatic brain injury

Progression of acute traumatic brain injury (TBI) into chronic neurodegeneration is a major health problem with no protective treatments. Here, we report that acutely elevated mitochondrial fission after TBI in mice triggers chronic neurodegeneration persisting 17 months later, equivalent to many human decades. We show that increased mitochondrial fission after mouse TBI is related to increased brain levels of mitochondrial fission 1 protein (Fis1) and that brain Fis1 is also elevated in human TBI. Pharmacologically preventing Fis1 from binding its mitochondrial partner, dynamin-related protein 1 (Drp1), for 2 weeks after TBI normalizes the balance of mitochondrial fission/fusion and prevents chronically impaired mitochondrial bioenergetics, oxidative damage, microglial activation and lipid droplet formation, blood-brain barrier deterioration, neurodegeneration, and cognitive impairment. Delaying treatment until 8 months after TBI offers no protection. Thus, time-sensitive inhibition of acutely elevated mitochondrial fission may represent a strategy to protect human TBI patients from chronic neurodegeneration.