ACA, an inhibitor phospholipases A2 and transient receptor potential melastatin-2 channels, attenuates okadaic acid induced neurodegeneration in rats

Targeting Transient Receptor Potential Melastatin-2 (TRPM2) Enhances Therapeutic Efficacy of Third Generation EGFR Inhibitors against EGFR Mutant Lung Cancer

There is an urgent need to fully understand the biology of third generation EGFR-tyrosine kinase inhibitors (EGFR-TKIs), particularly osimertinib, and to develop mechanism-driven strategies to manage their acquired resistance. Transient receptor potential melastatin-2 (TRPM2) functions as an important regulator of Ca2+ influx, but its role in mediating therapeutic efficacies of EGFR-TKIs and acquired resistance to EGFR-TKIs has been rarely studied. This study has demonstrated a previously undiscovered role of suppression of TRPM2 and subsequent inhibition of Ca2+ influx and induction of ROS and DNA damage in mediating apoptosis induction and the therapeutic efficacy of osimertinib against EGFR mutant NSCLC. The rebound elevation represents a key mechanism accounting for the emergence of acquired resistance to osimertinib and other third generation EGFR-TKIs. Accordingly, targeting TRPM2 is a potentially promising strategy for overcoming and preventing acquired resistance to osimertinib, warranting further study in this direction including the development of cancer therapy-optimized TRPM2 inhibitors.

Kolaviron neuroprotective effect against okadaic acid-provoked cognitive impairment

Alzheimer's disease (AD) is acknowledged as the main causative factor of dementia that affects millions of people around the world and is increasing at increasing pace. Okadaic acid (OA) is a toxic compound with ability to inhibit protein phosphatases and to induce tau protein hyperphosphorylation and Alzheimer's-like phenotype. Kolaviron (KV) is a bioflavonoid derived from Garcinia kola seeds with anti-antioxidative and anti-inflammation properties. The main goal of this study was to assess whether kolaviron can exert neuroprotective effect against okadaic acid-induced cognitive deficit. Rats had an intracerebroventricular (ICV) injection of OA and pretreated with KV at 50 or 100 mg/kg and examined for cognition besides histological and biochemical factors. OA group treated with KV at 100 mg/kg had less memory deficit in passive avoidance and novel object discrimination (NOD) tasks besides lower hippocampal levels of caspases 1 and 3, tumor necrosis factor α (TNFα) and interleukin 6 (IL-6) as inflammatory factors, reactive oxygen species (ROS), protein carbonyl, malondialdehyde (MDA), and phosphorylated tau (p-tau) and higher level of acetylcholinesterase (AChE) activity, mitochondrial integrity index, superoxide dismutase (SOD), and glutathione (GSH). Moreover, KV pretreatment at 100 mg/kg attenuated hippocampal CA1 neuronal loss and glial fibrillary acidic protein (GFAP) reactivity as a factor of astrogliosis. In summary, KV was able to attenuate cognitive fall subsequent to ICV OA which is partly mediated through its neuroprotective potential linked to mitigation of tau hyperphosphorylation, apoptosis, pyroptosis, neuroinflammation, and oxidative stress and also improvement of mitochondrial health.

Involvement of TRPM2 Channel on Doxorubicin-Induced Experimental Cardiotoxicity Model: Protective Role of Selenium

Doxorubicin (DOXR) is an important chemotherapeutic drug used in cancer treatment for many years. Several studies reported that the use of DOXR increased toxicity by causing an increase in oxidative stress (OS), especially in the heart. In this study, we investigated the protective effect of selenium (Se) and the role of transient receptor potential melastatin-2 (TRPM2) channel activation by using N-(p-amylcinnamoyl) anthranilic acid (ACA) in a model of DOXR-induced cardiotoxicity. Sixty female rats were equally divided into the control, dimethyl sulfoxide (DMSO), DOXR, DOXR + Se, DOXR + ACA, and DOXR + Se + ACA groups. Glutathione (GSH), glutathione peroxidase (GSH-Px), caspases (Cas) 3 and 9, interleukin 1β (IL-1β), tumor necrosis factor-α (TNF-α), reactive oxygen species (ROS), poly [ADP-ribose] polymerase 1 (PARP-1), and TRPM2 channel levels were measured by ELISA. In addition, histopathological examination was performed in cardiac tissues and TNF-α, caspase 3, and TRPM2 channel expression levels were determined immunohistochemically. The levels of GSH, GSH-Px, caspases 3 and 9, IL-1β, TNF-α, ROS, PARP-1, and TRPM2 channel in serum, and cardiac tissue in the DOXR group were higher than in the control and DMSO groups (p < 0.05). However, these parameters in Se and/or ACA treatment groups were lower than in the DOXR group (p < 0.05). Also, we determined that Se and/or ACA treatment together with DOXR application decreased the TNF-α, Cas-3, and TRPM2 channel expression levels in the cardiac tissue. The data showed that administration of Se and/or ACA treatment together with DOXR may be used as a therapeutic agent in preventing DOXR-induced cardiotoxicity.

Neuroprotective effect of transient receptor potential Vanilloid 1 agonist capsaicin in Alzheimer’s disease model induced with okadaic acid

BACKGROUND

The presence of Transient Receptor Potential Vanilloid 1 (TRPV1) channels was detected in many regions of the human and rat brain, including the cortex and hippocampus. TRPV1 channels have functions such as the modulation of synaptic transmission and plasticity and the regulation of cognitive functions. Previous studies conducted with TRPV1 agonists and antagonists show that this channel is associated with the neurodegenerative process. In the present study, the purpose was to investigate the effects of capsaicin, which is a TRPV1 agonist, and capsazepine, a TRPV1 antagonist, in the Alzheimer's Disease (AD) model that was induced by intracerebroventricular (ICV) administration of okadaic acid (OKA).

METHODS

The AD-like experimental model was created with bilateral ICV OKA injection. Intraperitoneal capsaicin and capsazepine injections were administered to the treatment groups for 13 days and histological and immunohistochemical examinations were performed from the cortex and hippocampal CA3 regions of the brain. The Morris Water Maze Test was used for spatial memory measurement.

RESULTS

ICV OKA administration increased the levels of caspase-3, phosphorylated-tau-(ser396), Aβ, TNF-α, and IL1-β, from the cortex and hippocampal CA3 regions of the brain and decreased the phosphorylated-Glycogen synthase kinase-3 beta-(ser9) levels. In addition, the OKA administration corrupted the spatial memory. The TRPV1 agonist capsaicin reversed the pathological changes induced by ICV OKA administration, but not the TRPV1 antagonist capsazepine.

CONCLUSIONS

It was found in the study that the administration of the TRPV1 agonist capsaicin reduced neurodegeneration, neuroinflammation, and deterioration in spatial memory in the AD model induced by OKA.

De novo design of DNA aptamers that target okadaic acid (OA) by docking-then-assembling of single nucleotides

Okadaic acid (OA) is a diarrhetic shellfish poison widespread in ocean, so its detection is of great significance to seafood safety. Because of good sensitivity and low cost, biosensors using nucleic-acid aptamers as the recognition molecules are emerging as an important detection tool. However, the traditional SELEX screening method for acquiring OA high-affinity aptamers is time- and resource-intensive. Alternatively, here we developed a de novo design method based on the 3D structure of a target molecule, such as OA. Without experimental screening, this method designs OA aptamers by a computational approach of docking-then-assembling (DTA) of single nucleotides (A, C, G and T) as: (1) determining the high-affinity nucleotide binding sites of the target molecule via saturated molecular docking; (2) assembling the bound nucleotides into binding units to the target molecule; (3) constructing full-length aptamers by introducing stabilizing units to connect these binding units. In this way, five OA aptamers were designed, and microscale thermophoresis (MST) experiments verified that their K_d values are in the range of 100-600 nM; and one of them (named 9CGAT_4_a) could specifically bind to OA with low affinities for the other three marine biotoxins. Therefore, this study provides high-affinity and specific aptamers for the development of OA biosensors, and presents a promising de novo design method applicable to other target molecules.

Sensitive detection of the okadaic acid marine toxin in shellfish by Au@Pt NPs/horseradish peroxidase dual catalysis immunoassay

Based on the catalysis enhancement strategy of Au@Pt nanoparticles (Au@Pt NPs) and horseradish peroxidase (HRP) related to the TMB-H₂O₂ indicator, a sensitive colorimetric immunoassay was established for trace okadaic acid (OA) detection. The anti-OA monoclonal antibody (McAb) with a high K_aff constant was prepared and modified on Au@Pt NPs. Through grafting the HRP conjugated goat anti-mouse IgG antibody (IgG) on Au@Pt/McAb, bifunctional composites with Au@Pt-Ab and HRP were prepared and adopted. Characteristics including morphology, specificity and catalytic performance were evaluated. Under the optimal conditions, the sensitivity of the resultant enzyme immunoassay was significantly improved, and a low limit of detection (LOD) of OA was achieved at 0.04 ng mL^-1 (equivalent to 0.6 μg kg^-1 in mussel tissue), which was better than that of most HRP or Au/HRP enzyme-linked immunosorbent assays. When applied to fortified shellfish samples (e.g. oysters, mussels and clams), the recoveries ranging from 98.3 ± 2.3% to 106.0 ± 9.0% were acceptable and comparable with those of the LC-MS method. Acceptable precision was achieved with a variation coefficient (CV) of 2.3-8.4%. The method provides a promising alternative for the highly sensitive detection of the OA marine toxin at trace levels.

TRPM2 in ischemic stroke: Structure, molecular mechanisms, and drug intervention

Ischemic stroke has a high lethality rate worldwide, and novel treatments are limited. Calcium overload is considered to be one of the mechanisms of cerebral ischemia. Transient receptor potential melastatin 2 (TRPM2) is a reactive oxygen species (ROS)-sensitive calcium channel. Cerebral ischemia-induced TRPM2 activation triggers abnormal intracellular Ca2+ accumulation and cell death, which in turn causes irreversible brain damage. Thus, TRPM2 has emerged as a new therapeutic target for ischemic stroke. This review provides data on the expression, structure, and function of TRPM2 and illustrates its cellular and molecular mechanisms in ischemic stroke. Natural and synthetic TRPM2 inhibitors (both specific and nonspecific) are also summarized. The three-dimensional protein structure of TRPM2 has been identified, and we speculate that molecular simulation techniques will be essential for developing new drugs that block TRPM2 channels. These insights about TRPM2 may be the key to find potent therapeutic approaches for the treatment of ischemic stroke.

Toxic Substance-induced Hippocampal Neurodegeneration in Rodents as Model of Alzheimer’s Dementia

BACKGROUND: Alzheimer’s Dementia (AD) cases are increasing with the global elderly population. To study the part of the brain affected by AD, animal models for hippocampal degeneration are still necessary to better understand AD pathogenesis and develop treatment and prevention measures. AIM: This study was a systematic review of toxic substance-induced animal models of AD using the Morris Water Maze method in determining hippocampal-related memory impairment. Our aim was reviewing the methods of AD induction using toxic substances in laboratory rodents and evaluating the report of the AD biomarkers reported in the models. METHODS: Data were obtained from articles in the PubMed database, then compiled, categorized, and analyzed. Eighty studies published in the past 5 years were included for analysis. RESULTS AND DISCUSSION: The most widely used method was intracerebroventricular injection of amyloid-β _substances. However, some less technically challenging techniques using oral or intraperitoneal administration of other toxic substances also produce successful models. Instead of hippocampal neurodegeneration, many studies detected biomarkers of the AD pathological process while some reported inflammation, oxidative stress, neurotrophic factors, and changes of cholinergic activity. Female animals were underrepresented despite a high incidence of AD in women. CONCLUSION: Toxic substances may be used to develop AD animal models characterized with appropriate AD pathological markers. Characterization of methods with the most easy-handling techniques and more studies in female animal models should be encouraged.

The Discovery of Novel ACA Derivatives as Specific TRPM2 Inhibitors that Reduce Ischemic Injury Both In Vitro and In Vivo

The transient receptor potential melastatin 2 (TRPM2) channel is associated with ischemia/reperfusion injury, inflammation, cancer, and neurodegenerative diseases. However, the limit of specific inhibitors impedes the development of TRPM2-targeted therapeutic agents. To discover more potent and selective TRPM2 inhibitors, 59 N-(p-amylcinnamoyl) anthranilic acid (ACA) derivatives were synthesized and evaluated using calcium imaging and electrophysiology approaches. Systematic structure-activity relationship studies resulted in some potent compounds inhibiting the TRPM2 channel with sub-micromolar half-maximal inhibitory concentration values. Among them, the preferred compound A23 exhibited TRPM2 selectivity over TRPM8 and TRPV1 channels as well as phospholipase A2 and showed neuroprotective activity in vitro. Following pharmacokinetic studies, A23 was further evaluated in a transient middle cerebral artery occlusion model in vivo, which significantly reduced cerebral infarction. These data indicate that A23 might serve as a useful tool for TRPM2-related research as well as a lead compound for the development of therapeutic agents for ischemic injury.

Medicinal chemistry perspective of TRPM2 channel inhibitors: where we are and where we might be heading?

Transient receptor potential melastatin 2 (TRPM2) is a Ca²⁺- permeable nonselective cation channel that is involved in diverse biological functions as a cellular sensor for oxidative stress and temperature. It has been considered a promising therapeutic target for the treatment of ischemia/reperfusion (IR) injury, inflammation, cancer, and neurodegenerative diseases. Development of highly potent and selective TRPM2 inhibitors and validation of their use in relevant disease models will advance drug discovery. In this review, we describe the molecular structures and gating mechanism of the TRPM2 channel, and offer a comprehensive review of advances in the discovery of TRPM2 inhibitors. Furthermore, we analyze the properties of reported TRPM2 inhibitors with an emphasis on how specific inhibitors targeting this channel could be better developed.

Curcumin-primed exosomes potently ameliorate cognitive function in AD mice by inhibiting hyperphosphorylation of the Tau protein through the AKT/GSK-3β pathway

Alzheimer's disease (AD) is the progressive development of fatal neurodegenerative diseases. Owing to the unclearness of the pathogenesis of AD and the failure of the drug to cross the blood-brain barrier (BBB), there is currently a lack of effective diagnostic and therapeutic approaches in the treatment of AD. The aim of this study was to design exosomes (Exo) as a specifically designed carrier able to carry curcumin (cur) to prevent neuronal death in vitro and in vivo to alleviate the AD symptoms. Our results demonstrated that Exo improved the solubility and bioavailability of cur and increased drug penetration across the BBB by specific active targeting between Exo, inheriting the lymphocyte function-associated antigen 1 (LFA-1) and endothelial intercellular adhesion molecule 1 (ICAM-1). Exosomes derived from curcumin-treated (primed) cells (Exo-cur) can better prevent the death of neurons in vitro and in vivo to relieve the symptoms of AD by inhibiting phosphorylation of the Tau protein through activating the AKT/GSK-3β pathway. Our results suggested that Exo-cur featured highly effective BBB-crossing via receptor-mediated transcytosis to access brain tissues and inhibited Tau phosphorylation, holding great potential in improving targeted drug delivery and the recovery of neuronal function in AD therapy.

Galangin decreases p‑tau, Aβ42 and β‑secretase levels, and suppresses autophagy in okadaic acid‑induced PC12 cells via an Akt/GSK3β/mTOR signaling‑dependent mechanism

Okadaic acid (OA)‑induced neurotoxicity may be considered a novel tool used to study Alzheimer's disease (AD) pathology, and may be helpful in the development of a novel therapeutic approach. It has been reported that galangin inhibits β‑site amyloid precursor protein‑cleaving enzyme 1 expression, which is a key enzyme for amyloid β (Aβ) generation and is a potential drug candidate for AD therapy. However, further studies are required to confirm its neuroprotective effects in other AD models. The present study aimed to explore the neuroprotective effects of galangin on OA‑induced neurotoxicity in PC12 cells. The cells were divided into the following groups: Control group, model group (175 nM OA for 48 h) and galangin groups (0.25, 0.5 and 1 µg/ml). Beclin‑1, phosphorylated (p)‑protein kinase B (Akt), p‑glycogen synthase kinase (GSK)3β and p‑mechanistic target of rapamycin (mTOR) expression was also measured in the following PC12 cell groups: Control group, model group, 3‑methyladenine group (5 nM), rapamycin group (100 nM) and galangin group (1 µg/ml). The levels of β‑secretase, Aβ42 and p‑tau were detected by ELISA, Beclin‑1 expression was examined by immunohistochemistry and the protein expression levels of p‑Akt, p‑mTOR p‑GSK3β, and Beclin‑1 were detected by western blotting. Galangin treatment enhanced cell viability in cells treated with OA, and decreased β‑secretase, Aβ42 and p‑tau levels. In addition, it suppressed Beclin‑1 and p‑GSK3β expression, but promoted p‑Akt and p‑mTOR expression by regulating the Akt/GSK3β/mTOR pathway. These results indicated that galangin protected PC12 cells from OA‑induced cytotoxicity and inhibited autophagy via the Akt/GSK3β/mTOR pathway, thus suggesting that it may be considered a potential therapeutic agent for AD.

Protective effect of N-(p-amylcinnamoyl) anthranilic acid, phospholipase A2 enzyme inhibitor, and transient receptor potential melastatin-2 channel blocker against renal ischemia-reperfusion injury

The production of reactive oxygen species and inflammatory events are the underlying mechanisms of ischemia-reperfusion injury (IRI). It was determined that transient receptor potential melastatin-2 (TRPM2) channels and phospholipase A₂ (PLA ₂ ) enzymes were associated with inflammation and cell death. In this study, we investigated the effect of N-( p-amylcinnamoyl) anthranilic acid (ACA), a TRPM2 channel blocker, and PLA ₂ enzyme inhibitor on renal IRI. A total of 36 male Sprague-Dawley rats were divided into four groups: control, ischemia-reperfusion (I/R), I/R + ACA 5 mg, I/R + ACA 25 mg. In I/R applied groups, the ischemia for 45 minutes and reperfusion for 24 hours were applied bilaterally to the kidneys. In the I/R group, serum levels of the blood urea nitrogen (BUN), creatinine, cystatin C (CysC), kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and interleukin-18 increased. On histopathological examination of renal tissue in the I/R group, the formation of glomerular and tubular damage was seen, and it was detected that there was an increase in the levels of malondialdehyde (MDA), caspase-3, total oxidant status (TOS), and oxidative stress index (OSI); and there was a decrease in total antioxidant capacity (TAC) and catalase enzyme activity. ACA administration reduced serum levels of BUN, creatinine, CysC, KIM-1, NGAL, interleukin-18. In the renal tissue, ACA administration reduced histopathological damage, levels of caspase-3, MDA, TOS, and OSI; and it increased the level of TAC and catalase enzyme activity. It has been shown with the histological and biochemical results in this study that ACA is protective against renal IRI.

8-Br-cADPR, a TRPM2 ion channel antagonist, inhibits renal ischemia-reperfusion injury

The transient receptor potential melastatin-2 (TRPM2) channel belongs to the transient receptor potential channel superfamily and is a cation channel permeable to Na⁺ and Ca ²⁺ . The TRPM2 ion channel is expressed in the kidney and can be activated by various molecules such as hydrogen peroxide, calcium, and cyclic adenosine diphosphate (ADP)-ribose (cADPR) that are produced during acute kidney injury. In this study, we investigated the role of 8-bromo-cyclic ADP-ribose (8-Br-cADPR; a cADPR antagonist) in renal ischemia-reperfusion injury using biochemical and histopathological parameters. CD38, cADPR, tumor necrosis factor-α, interleukin-1β, and myeloperoxidase (inflammatory markers), urea and creatinine, hydrogen peroxide (oxidant), and catalase (antioxidant enzyme) levels that increase with ischemia-reperfusion injury decreased in the groups treated with 8-Br-cADPR. In addition, renin levels were elevated in the groups treated with 8-Br-cADPR. Histopathological examination revealed that 8-Br-cADPR reduced renal damage and the expression of caspase-3 and TRPM2. Our results suggest that the inhibition of TRPM2 ion channel may be a new treatment modality for ischemic acute kidney injury.