Paraoxon: An Anticholinesterase That Triggers an Excitotoxic Cascade of Oxidative Stress, Adhesion Responses, and Synaptic Compromise

The anticholinesterase paraoxon (Pxn) is an organophosphate (OP) and the active metabolite of the insecticide parathion. It potently inhibits the enzyme acetylcholinesterase and leads to enhanced glutamate release, diminished GABA uptake, oxidative damage, and neurodegeneration. The resulting increased levels of acetylcholine can trigger seizures and cause neuronal and excitotoxic damage in the brain. The brain susceptibility related to anticholinesterase toxins extends beyond potential brain damage and death from toxic levels of the agent. Asymptomatic low-level exposure to such toxins can also leave the brain vulnerable or even cause it to exhibit neurological problems later in life. The actions of Pxn and similar neurotoxins have been studied in order to examine the events associated with anticholinesterase toxicity in the brain. A recent study demonstrated that Pxn exposure initiates a pathogenic cascade involving seizure events and subsequent signs of damage including unique presynaptic vulnerability and associated behavioral deficits. In addition, Pxn-mediated synaptotoxicity is also associated with enhanced production of oxidative stress as well as integrin adhesion responses. These findings provide a better understanding of the molecular events involved in Pxn toxicity

Effect of glycine on prelethal and postlethal increases in calpain activity in rat renal proximal tubules

Effect of glycine on prelethal and postlethal increases in calpain activity in rat renal proximal tubules. The effect of glycine on hypoxia- and ionomycin-induced increases in calpain activity in rat proximal tubules was determined. Calpain activity was determined both in vitro and in the intact cell using the fluorescent substrate N-succinyl-Leu-Leu-Val-Tyr-7- amido-4-methyl coumarin (N-succinyl-Leu-Leu-Val-Tyr-AMC) and Western blotting for calpain-specific spectrin breakdown products (BDP), respectively. At 7.5 minutes of hypoxia (prelethal injury model) there was a significant (10-fold) increase in in vitro calpain activity that was not inhibited by glycine. At 15 minutes of hypoxia (postlethal injury model) there was a further increase in calpain activity that was inhibited by glycine. Normoxic tubules incubated with the calcium ionophore ionomy-cin (5 µM) for two minutes and 10 minutes had a significant increase in calpain activity that was not inhibited by glycine. After 15 minutes of hypoxia in the presence of glycine, there was an increase in calpain-specific spectrin breakdown products (BDP) in both Triton X-100 soluble and cytosolic extracts from proximal tubules. Glycine in concentrations up to 10mM had no direct effect on the in vitro calpain activity of purified calpains. The present study demonstrates that: (1) prelethal increases in calpain activity stimulated by hypoxia and ionomycin treatment are not affected by glycine; (2) calpain-mediated spectrin breakdown during hypoxia occurs in the presence of glycine; (3) glycine does prevent the additional postlethal increase in calpain activity probably by maintaining membrane integrity to calcium influx

Limit theorems for sums of random exponentials

We study limiting distributions of exponential sums $S_N(t)=\sum_{i=1}^N e^{tX_i}$ as $t\to\infty$, $N\to\infty$, where $(X_i)$ are i.i.d.\ random variables. Two cases are considered: (A) \esssup X_i=0 and (B) \esssup X_i=\infty. We assume that the function $h(x)=-\log P(X_i>x)$ (case B) or $h(x)=-\log P(X_i>-1/x)$ (case A) is regularly varying at $\infty$ with index $1<\varrho<\infty$ (case B) or $0<\varrho<\infty$ (case A). The appropriate growth scale of $N$ relative to $t$ is of the form $e^{\lambda H_0(t)}$ ($0<\lambda<\infty$), where the rate function $H_0(t)$ is a certain asymptotic version of the function $H(t)=\log E [e^{tX_i}]$ (case B) or $H(t)=-\log E [e^{tX_i}]$ (case A). We have found two critical points, $\lambda_{1}<\lambda_{2}$, below which the Law of Large Numbers and the Central Limit Theorem, respectively, break down. For $0<\lambda<\lambda_{2}$, under the slightly stronger condition of normalized regular variation of $h$ we prove that the limit laws are stable, with characteristic exponent $\alpha=\alpha(\varrho,\lambda)\in(0,2)$ and skewness parameter $\beta\equiv1$

Cellular/Molecular Dual Modulation of Endocannabinoid Transport and Fatty Acid Amide Hydrolase Protects against Excitotoxicity

The endocannabinoid system has been suggested to elicit signals that defend against several disease states including excitotoxic brain damage. Besides direct activation with CB 1 receptor agonists, cannabinergic signaling can be modulated through inhibition of endocannabinoid transport and fatty acid amide hydrolase (FAAH), two mechanisms of endocannabinoid inactivation. To test whether the transporter and FAAH can be targeted pharmacologically to modulate survival/repair responses, the transport inhibitor N-(4-hydroxyphenyl)-arachidonamide (AM404) and the FAAH inhibitor palmitylsulfonyl fluoride (AM374) were assessed for protection against excitotoxicity in vitro and in vivo. AM374 and AM404 both enhanced mitogen-activated protein kinase (MAPK) activation in cultured hippocampal slices. Interestingly, combining the distinct inhibitors produced additive effects on CB 1 signaling and associated neuroprotection. After an excitotoxic insult in the slices, infusing the AM374/AM404 combination protected against cytoskeletal damage and synaptic decline, and the protection was similar to that produced by the stable CB 1 agonist AM356 (R-methanandamide). AM374/ AM404 and the agonist also elicited cytoskeletal and synaptic protection in vivo when coinjected with excitotoxin into the dorsal hippocampus. Correspondingly, potentiating endocannabinoid responses with the AM374/AM404 combination prevented behavioral alterations and memory impairment that are characteristic of excitotoxic damage. The protective effects mediated by AM374/AM404 were (1) evident 7 d after insult, (2) correlated with the preservation of CB 1 -linked MAPK signaling, and (3) were blocked by a selective CB 1 antagonist. These results indicate that dual modulation of the endocannabinoid system with AM374/AM404 elicits neuroprotection through the CB 1 receptor. The transporter and FAAH are modulatory sites that may be exploited to enhance cannabinergic signaling for therapeutic purposes

Blast waves from detonated military explosive reduce GluR1 and synaptophysin levels in hippocampal slice cultures

Explosives create shockwaves that cause blast-induced neurotrauma, one of the most common types of traumatic brain injury (TBI) linked to military service. Blast-induced TBIs are often associated with reduced cognitive and behavioral functions due to a variety of factors. To study the direct effects of military explosive blasts on brain tissue, we removed systemic factors by utilizing rat hippocampal slice cultures. The long-term slice cultures were briefly sealed air-tight in serum-free medium, lowered into a 37 °C water-filled tank, and small 1.7-gram assemblies of cyclotrimethylene trinitramine (RDX) were detonated 15 cm outside the tank, creating a distinct shockwave recorded at the culture plate position. Compared to control mock-treated groups of slices that received equal submerge time, 1–3 blast impacts caused a dose-dependent reduction in the AMPA receptor subunit GluR1. While only a small reduction was found in hippocampal slices exposed to a single RDX blast and harvested 1–2 days later, slices that received two consecutive RDX blasts 4 min apart exhibited a 26–40% reduction in GluR1, and the receptor subunit was further reduced by 64–72% after three consecutive blasts. Such loss correlated with increased levels of HDAC2, a histone deacetylase implicated in stress-induced reduction of glutamatergic transmission. No evidence of synaptic marker recovery was found at 72 h post-blast. The presynaptic marker synaptophysin was found to have similar susceptibility as GluR1 to the multiple explosive detonations. In contrast to the synaptic protein reductions, actin levels were unchanged, spectrin breakdown was not detected, and Fluoro-Jade B staining found no indication of degenerating neurons in slices exposed to three RDX blasts, suggesting that small, sub-lethal explosives are capable of producing selective alterations to synaptic integrity. Together, these results indicate that blast waves from military explosive cause signs of synaptic compromise without producing severe neurodegeneration, perhaps explaining the cognitive and behavioral changes in those blast-induced TBI sufferers that have no detectable neuropathology

Potential Alzheimer’s Disease Therapeutics Among Weak Cysteine Protease Inhibitors Exhibit Mechanistic Differences Regarding Extent of Cathepsin B Up-Regulation and Ability to Block Calpain

Cysteine protease inhibitors have long been part of drug discovery programs for Alzheimer's disease (AD), traumatic brain injury (TBI), and other disorders. Select inhibitors reduce accumulating proteins and AD pathology in mouse models. One such compound, Z-Phe-Aladiazomethylketone (PADK), exhibits a very weak IC50 (9-11 μM) towards cathepsin B (CatB), but curiously PADK causes marked up-regulation of the Aβ-degrading CatB and improves spatial memory. Potential therapeutic and weak inhibitor E64d (14 μM IC50) also up-regulates CatB. PADK and E64d were compared regarding the blockage of calcium-induced cytoskeletal deterioration in brain samples, monitoring the 150-kDa spectrin breakdown product (SBDP) known to be produced by calpain. PADK had little to no effect on SBDP production at 10-100 μM. In contrast, E64d caused a dosedependent decline in SBDP levels with an IC50 of 3-6 μM, closely matching its reported potency for inhibiting μ-calpain. Calpain also cleaves the cytoskeletal organizing protein gephyrin, producing 49-kDa (GnBDP49) and 18-kDa (GnBDP18) breakdown products. PADK had no apparent effect on calcium-induced gephyrin fragments whereas E64d blocked their production. E64d also protected the parent gephyrin in correspondence with reduced BDP levels. The findings of this study indicate that PADK’s positive and selective effects on CatB are consistent with human studies showing exercise elevates CatB and such elevation correlates with improved memory. On the other hand, E64d exhibits both marginal CatB enhancement and potent calpain inhibition. This dual effect may be beneficial for treating AD. Alternatively, the potent action on calpain-related pathology may explain E64d’s protection in AD and TBI models

Investıgatıon of Removal of Dye from Aqueous Solutıon by Advanced Treatment

The textile dyeing and finishing industry use a significant amount of water and produce water pollution. Conventional biological treatment processes have some difficulties for degradation of nonbiodegradable compounds. Dye-bearing wastewaters have high COD and colour. In this study, a photo reactor process was used to remove color from aqueous solution.Effects of pH on Reactive Red 4 and cationic dye removal using 1g/L TiO2, as catalyst were studied at constant inital dye concentration (25 mg/l). Cationic dye removal efficiency is better than Reactive dye removal efficiency for photocatalytic oxidation in this stud

Role of the Proteasome in Excitotoxicity-Induced Cleavage of Glutamic Acid Decarboxylase in Cultured Hippocampal Neurons

Glutamic acid decarboxylase is responsible for synthesizing GABA, the major inhibitory neurotransmitter, and exists in two isoforms—GAD65 and GAD67. The enzyme is cleaved under excitotoxic conditions, but the mechanisms involved and the functional consequences are not fully elucidated. We found that excitotoxic stimulation of cultured hippocampal neurons with glutamate leads to a time-dependent cleavage of GAD65 and GAD67 in the N-terminal region of the proteins, and decrease the corresponding mRNAs. The cleavage of GAD67 was sensitive to the proteasome inhibitors MG132, YU102 and lactacystin, and was also abrogated by the E1 ubiquitin ligase inhibitor UBEI-41. In contrast, MG132 and UBEI-41 were the only inhibitors tested that showed an effect on GAD65 cleavage. Excitotoxic stimulation with glutamate also increased the amount of GAD captured in experiments where ubiquitinated proteins and their binding partners were isolated. However, no evidences were found for direct GADs ubiquitination in cultured hippocampal neurons, and recombinant GAD65 was not cleaved by purified 20S or 26S proteasome preparations. Since calpains, a group of calcium activated proteases, play a key role in GAD65/67 cleavage under excitotoxic conditions the results suggest that GADs are cleaved after ubiquitination and degradation of an unknown binding partner by the proteasome. The characteristic punctate distribution of GAD65 along neurites of differentiated cultured hippocampal neurons was significantly reduced after excitotoxic injury, and the total GAD activity measured in extracts from the cerebellum or cerebral cortex at 24h postmortem (when there is a partial cleavage of GADs) was also decreased. The results show a role of the UPS in the cleavage of GAD65/67 and point out the deregulation of GADs under excitotoxic conditions, which is likely to affect GABAergic neurotransmission. This is the first time that the UPS has been implicated in the events triggered during excitotoxicity and the first molecular target of the UPS affected in this cell death process

International Olympic Committee consensus statement: Methods for recording and reporting of epidemiological data on injury and illness in sport 2020 (including STROBE Extension for Sport Injury and Illness Surveillance (STROBE-SIIS))

Injury and illness surveillance, and epidemiological studies, are fundamental elements of concerted efforts to protect the health of the athlete. To encourage consistency in the definitions and methodology used, and to enable data across studies to be compared, research groups have published 11 sport-specific or setting-specific consensus statements on sports injury (and, eventually, illness) epidemiology to date. Our objective was to further strengthen consistency in data collection, injury definitions and research reporting through an updated set of recommendations for sports injury and illness studies, including a new Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist extension. The IOC invited a working group of international experts to review relevant literature and provide recommendations. The procedure included an open online survey, several stages of text drafting and consultation by working groups and a 3-day consensus meeting in October 2019. This statement includes recommendations for data collection and research reporting covering key components: defining and classifying health problems; severity of health problems; capturing and reporting athlete exposure; expressing risk; burden of health problems; study population characteristics and data collection methods. Based on these, we also developed a new reporting guideline as a STROBE Extension -the STROBE Sports Injury and Illness Surveillance (STROBE-SIIS). The IOC encourages ongoing in-and out-of-competition surveillance programmes and studies to describe injury and illness trends and patterns, understand their causes and develop measures to protect the health of the athlete. Implementation of the methods outlined in this statement will advance consistency in data collection and research reporting. © Author(s) (or their employer(s)) 2020