Levetiracetam prevents neurophysiological changes and preserves cognitive function in the HIV-1 TAT transgenic mouse model of HIV-associated neurocognitive disorder.

HIV-associated neurocognitive disorder (HAND) affects nearly half of the 39 million people living with HIV. HAND symptoms range from subclinical cognitive impairment to dementia; the mechanisms that underlie HAND remain unclear and there is no treatment. The HIV-protein transactivator of transcription (TAT) is thought to contribute to HAND because it persists in the CNS and elicits neurotoxicity in animal models. Network hyperexcitability is associated with accelerated cognitive decline in neurodegenerative disorders. Here, we show that the antiepileptic drug levetiracetam (LEV) attenuated aberrant excitatory synaptic transmission, protected synaptic plasticity, reduced seizure susceptibility, and preserved cognition in inducible TAT (iTAT) transgenic male mice. iTAT mice had an increased frequency of spontaneous excitatory postsynaptic currents in hippocampal slice recordings and impaired long-term potentiation, a form of synaptic plasticity that underlies learning and memory. Two-week administration of LEV by osmotic minipump prevented both impairments. Kainic acid administered to iTAT mice induced a higher maximum behavioral seizure score, longer seizure duration, and a shorter latency to first seizure, consistent with a lower seizure threshold. LEV treatment prevented these in vivo signs of hyperexcitability. Lastly, in the Barnes maze, iTAT mice required more time to reach the goal, committed more errors, and received lower cognitive scores relative to iTAT mice treated with LEV. Thus, TAT expression drives functional deficits, suggesting a causative role in HAND. As LEV not only prevented aberrant synaptic activity in iTAT mice, but also prevented cognitive dysfunction, it may provide a promising pharmacological approach to the treatment of HAND. Significance Statement Around half of people living with HIV also suffer from HIV-associated neurocognitive disorder (HAND), for which there is no treatment. The HIV protein TAT causes toxicity that is thought to contribute to HAND. Here, we show that an antiepileptic drug, levetiracetam (LEV), prevented synaptic and cognitive impairments that develop in a TAT-expressing mouse. LEV is widely used to treat seizures and is well-tolerated in humans, including those with HIV. This study supports further investigation of LEV-treatment for neuroprotection in HAND.

The little brain and the seahorse: Cerebellar-hippocampal interactions.

There is a growing appreciation for the cerebellum beyond its role in motor function and accumulating evidence that the cerebellum and hippocampus interact across a range of brain states and behaviors. Acute and chronic manipulations, simultaneous recordings, and imaging studies together indicate coordinated coactivation and a bidirectional functional connectivity relevant for various physiological functions, including spatiotemporal processing. This bidirectional functional connectivity is likely supported by multiple circuit paths. It is also important in temporal lobe epilepsy: the cerebellum is impacted by seizures and epilepsy, and modulation of cerebellar circuitry can be an effective strategy to inhibit hippocampal seizures. This review highlights some of the recent key hippobellum literature.

Taccalonolide C-6 Analogues, Including Paclitaxel Hybrids, Demonstrate Improved Microtubule Polymerizing Activities.

The C-22,23-epoxy taccalonolides are microtubule stabilizers that bind covalently to ß-tubulin with a high degree of specificity. We semisynthesized and performed biochemical and cellular evaluations on 20 taccalonolide analogues designed to improve target engagement. Most notably, modification of C-6 on the taccalonolide backbone with the C-13 N-acyl-ß-phenylisoserine side chain of paclitaxel provided compounds with 10-fold improved potency for biochemical tubulin polymerization as compared to that of the unmodified epoxy taccalonolide AJ. Covalent docking demonstrated that the C-13 paclitaxel side chain occupied a binding pocket adjacent to the core taccalonolide pocket near the M-loop of ß-tubulin. Although paclitaxel-taccalonolide hybrids demonstrated improved in vitro biochemical potency, they retained features of the taccalonolide chemotype, including a lag in tubulin polymerization and high degree of cellular persistence after drug washout associated with covalent binding. Together, these data demonstrate that C-6 modifications can improve the target engagement of this covalent class of microtubule drugs without substantively changing their mechanism of action.

Synthesis and Biological Evaluations of Electrophilic Steroids Inspired by the Taccalonolides.

Natural products have served as inspirational scaffolds for the design and synthesis of novel antineoplastic agents. Here we present our preliminary efforts on the synthesis and biological evaluation of a new class of electrophilic steroids inspired by the naturally occurring taccalonolides. We demonstrate that these simplified analogs exhibit highly persistent antiproliferative properties similar to the taccalonolides and retain activity against resistant cancer cell lines that warrants further preclinical development.

Prevention of brain damage after traumatic brain injury by pharmacological enhancement of KCNQ (Kv7, "M-type") K+ currents in neurons.

Nearly three million people in the USA suffer traumatic brain injury (TBI) yearly; however, there are no pre- or post-TBI treatment options available. KCNQ2-5 voltage-gated K+ channels underlie the neuronal "M current", which plays a dominant role in the regulation of neuronal excitability. Our strategy towards prevention of TBI-induced brain damage is predicated on the suggested hyper-excitability of neurons induced by TBIs, and the decrease in neuronal excitation upon pharmacological augmentation of M/KCNQ K+ currents. Seizures are very common after a TBI, making further seizures and development of epilepsy disease more likely. Our hypothesis is that TBI-induced hyperexcitability and ischemia/hypoxia lead to metabolic stress, cell death and a maladaptive inflammatory response that causes further downstream morbidity. Using the mouse controlled closed-cortical impact blunt TBI model, we found that systemic administration of the prototype M-channel "opener", retigabine (RTG), 30 min after TBI, reduces the post-TBI cascade of events, including spontaneous seizures, enhanced susceptibility to chemo-convulsants, metabolic stress, inflammatory responses, blood-brain barrier breakdown, and cell death. This work suggests that acutely reducing neuronal excitability and energy demand via M-current enhancement may be a novel model of therapeutic intervention against post-TBI brain damage and dysfunction.

Functional responses of the hippocampus to hyperexcitability depend on directed, neuron-specific KCNQ2 K+ channel plasticity.

M-type (KCNQ2/3) K+ channels play dominant roles in regulation of active and passive neuronal discharge properties such as resting membrane potential, spike-frequency adaptation, and hyper-excitatory states. However, plasticity of M-channel expression and function in nongenetic forms of epileptogenesis are still not well understood. Using transgenic mice with an EGFP reporter to detect expression maps of KCNQ2 mRNA, we assayed hyperexcitability-induced alterations in KCNQ2 transcription across subregions of the hippocampus. Pilocarpine and pentylenetetrazol chemoconvulsant models of seizure induction were used, and brain tissue examined 48 hr later. We observed increases in KCNQ2 mRNA in CA1 and CA3 pyramidal neurons after chemoconvulsant-induced hyperexcitability at 48 hr, but no significant change was observed in dentate gyrus (DG) granule cells. Using chromogenic in situ hybridization assays, changes to KCNQ3 transcription were not detected after hyper-excitation challenge, but the results for KCNQ2 paralleled those using the KCNQ2-mRNA reporter mice. In mice 7 days after pilocarpine challenge, levels of KCNQ2 mRNA were similar in all regions to those from control mice. In brain-slice electrophysiology recordings, CA1 pyramidal neurons demonstrated increased M-current amplitudes 48 hr after hyperexcitability; however, there were no significant changes to DG granule cell M-current amplitude. Traumatic brain injury induced significantly greater KCNQ2 expression in the hippocampal hemisphere that was ipsilateral to the trauma. In vivo, after a secondary challenge with subconvulsant dose of pentylenetetrazole, control mice were susceptible to tonic-clonic seizures, whereas mice administered the M-channel opener retigabine were protected from such seizures. This study demonstrates that increased excitatory activity promotes KCNQ2 upregulation in the hippocampus in a cell-type specific manner. Such novel ion channel expressional plasticity may serve as a compensatory mechanism after a hyperexcitable event, at least in the short term. The upregulation described could be potentially leveraged in anticonvulsant enhancement of KCNQ2 channels as therapeutic target for preventing onset of epileptogenic seizures.

Triple-negative breast cancer cell line sensitivity to englerin A identifies a new, targetable subtype.

PURPOSE: Triple-negative breast cancers (TNBCs) represent a heterogeneous group of tumors. The lack of targeted therapies combined with the inherently aggressive nature of TNBCs results in a higher relapse rate and poorer overall survival. We evaluated the heterogeneity of TNBC cell lines for TRPC channel expression and sensitivity to cation-disrupting drugs. METHODS: The TRPC1/4/5 agonist englerin A was used to identify a group of TNBC cell lines sensitive to TRPC1/4/5 activation and intracellular cation disruption. Quantitative RT-PCR, the sulforhodamine B assay, pharmacological inhibition, and siRNA-mediated knockdown approaches were employed. Epifluorescence imaging was performed to measure intracellular Ca2+ and Na+ levels. Mitochondrial membrane potential changes were monitored by confocal imaging. RESULTS: BT-549 and Hs578T cells express high levels of TRPC4 and TRPC1/4, respectively, and are exquisitely, 2000- and 430-fold, more sensitive to englerin A than other TNBC cell lines. While englerin A caused a slow Na+ and nominal Ca2+ accumulation in Hs578T cells, it elicited rapid increases in cytosolic Ca2+ levels that triggered mitochondrial depolarization in BT-549 cells. Interestingly, BT-549 and Hs578T cells were also more sensitive to digoxin as compared to other TNBC cell lines. Collectively, these data reveal TRPC1/4 channels as potential biomarkers of TNBC cell lines with dysfunctional mechanisms of cation homeostasis and therefore sensitivity to cardiac glycosides. CONCLUSIONS: The sensitivity of BT-549 and Hs578T cells to englerin A and digoxin suggests a subset of TNBCs are highly susceptible to cation disruption and encourages investigation of TRPC1 and TRPC4 as potential new biomarkers of sensitivity to cardiac glycosides.