Genetic or Pharmacological Ablation of Acid-Sensing Ion Channel 1a (ASIC1a) Is Not Neuroprotective in a Mouse Model of Spinal Cord Injury.

Acid-sensing ion channel 1a (ASIC1a) is a proton-activated channel that is expressed ubiquitously throughout the central nervous system and in various types of immune cells. Its role in spinal cord injury (SCI) is controversial; inhibition of ASIC1a has been reported to improve SCI pathology in vivo, but conversely, gene ablation increased kainite-mediated excitotoxic cell death in vitro. Here, we re-examined the role of ASIC1a in a mouse model of SCI. First, we observed functional outcomes up to 42 days post-operation (DPO) in SCI mice with a selective genetic ablation of ASIC1a. Mice lacking ASIC1a had significantly worsened locomotor ability and increased lesion size compared with mice possessing the ASIC1a gene. Next, we explored pharmacological antagonism of this ion channel by administering the potent ASIC1a inhibitor, Hi1a. Consistent with a role for ASIC1a to attenuate excitotoxicity, accelerated neuronal cell loss was found at the lesion site in SCI mice treated with Hi1a, but there were no differences in locomotor recovery. Moreover, ASIC1a inhibition did not cause significant alterations to neutrophil migration, microglial density, or blood-spinal cord barrier integrity.

Single and dual tandem gait assessment post concussion: What performance time is clinically relevant across adult ages and what can influence results?

AIM: The three-metre tandem gait test (TG) is used to assess postural control during locomotion following sports concussion. However, values used to determine a pass/fail result are currently based on young athletic populations. Times for test completion may be influenced by several intrinsic or extrinsic factors. The aim of this study was to collate healthy individual single, dual task as well as dual task cost - motor TG times for a non-elite athlete population, across several age groups, and to investigate several potential influencing factors. METHODS: Healthy individuals aged 18-55+, who had never experienced a concussion completed single and dual task TG following the SCAT5 protocol. A separate group (n = 20, age, foot length and body mass index matched) performed the tests with alternate instructions. RESULTS: Mean best TG time for all participants were: single task 21.03 (±5.26s), dual task 29.59 (±9.84s) and DTC-motor 8.57 (±7.5s:41.7%). Age and foot length but not specificity of verbal instructions were related to TG times. Significantly slower single and dual task times were identified for the 55 + age group when compared to the three youngest groups (p < 0.01). No difference was seen for DTC-motor time or % between age groups (p > 0.05). CONCLUSION: Healthy individual data collected exceeded previously reported average times. Faster times were evident in younger participants and those with longer foot length. Results from this study can be used as a reliable guideline to inform clinical decisions around the pass/fail result of TGT across age ranges in non-elite athlete populations post-concussion.

Inhibition of Interleukin 1ß (IL-1ß) Expression by Anthrax Lethal Toxin (LeTx) Is Reversed by Histone Deacetylase 8 (HDAC8) Inhibition in Murine Macrophages.

Many pathogenic microbes often release toxins that subvert the host's immune responses to render the environment suitable for their survival and proliferation. LeTx is one of the toxins causing immune paralysis by cleaving and inactivating the mitogen-activated protein kinase (MAPK) kinases (MEKs). Here, we show that inhibition of the histone deacetylase 8 (HDAC8) by either the HDAC8-specific inhibitor PCI-34051 or small interference (si)RNAs rendered LeTx-exposed murine macrophages responsive to LPS in pro-IL-1ß production. HDAC8 selectively targeted acetylated histone H3 lysine 27 (H3K27Ac), which is known to associate with active enhancers. LeTx induced HDAC8 expression, in part through inhibiting p38 MAPK, which resulted in a decrease of H3K27Ac levels. Inhibition of HDAC8 increased H3K27Ac levels and enhanced NF-κB-mediated pro-IL-1ß enhancer and messenger RNA production in LeTx-exposed macrophages. Collectively, this study demonstrates a novel role of HDAC8 in LeTx immunotoxicity and regulation of pro-IL-1ß production likely through eRNAs. Targeting HDAC8 could be a strategy for enhancing immune responses in macrophages exposed to LeTx or other toxins that inhibit MAPKs.

HDAC8-mediated epigenetic reprogramming plays a key role in resistance to anthrax lethal toxin-induced pyroptosis in macrophages.

Macrophages pre-exposed to a sublethal dose of anthrax lethal toxin (LeTx) are refractory to subsequent high cytolytic doses of LeTx, termed toxin-induced resistance (TIR). A small population of TIR cells (2-4%) retains TIR characteristics for up to 5-6 wk. Through studying these long-term TIR cells, we found that a high level of histone deacetylase (HDAC)8 expression was crucial for TIR. Knocking down or inhibition of HDAC8 by small interfering RNAs or the HDAC8-specific inhibitor PCI-34051, respectively, induced expression of the mitochondrial death genes Bcl2 adenovirus E1B 19 kDa-interacting protein 3 (BNIP3), BNIP3-like and metastatic lymph node 64, and resensitized TIR cells to LeTx. Among multiple histone acetylations, histone H3 lysine 27 (H3K27) acetylation was most significantly decreased in TIR cells in an HDAC8-dependent manner, and the association of H3K27 acetylation with the genomic regions of BNIP3 and metastatic lymph node 64, where HDAC8 was recruited to, was diminished in TIR cells. Furthermore, overexpression of HDAC8 or knocking down the histone acetyltransferase CREB-binding protein/p300, known to target H3K27, rendered wild-type cells resistant to LeTx. As in RAW264.7 cells, primary bone marrow-derived macrophages exposed to a sublethal dose of LeTx were resistant to LeTx in an HDAC8-dependent manner. Collectively, this study demonstrates that epigenetic reprogramming mediated by HDAC8 plays a key role in determining the susceptibility of LeTx-induced pyroptosis in macrophages.