Calcium entry through L-type calcium channels causes mitochondrial disruption and chromaffin cell death

Targeting calciumopathy for neuroprotection: focus on calcium channels Cav1, Orai1 and P2X7

As the uncontrolled entry of calcium ions (Ca2+) through plasmalemmal calcium channels is a cell death trigger, the conjecture is here raised that mitigating such an excess of Ca2+ entry should rescue from death the vulnerable neurons in neurodegenerative diseases (NDDs). However, this supposition has failed in some clinical trials (CTs). Thus, a recent CT tested whether isradipine, a blocker of the Cav1 subtype of voltage-operated calcium channels (VOCCs), exerted a benefit in patients with Parkinson's disease (PD); however, outcomes were negative. This is one more of the hundreds of CTs done under the principle of one-drug-one-target, that have failed in Alzheimer's disease (AD) and other NDDs during the last three decades. As there are myriad calcium channels to let Ca2+ ions gain the cell cytosol, it seems reasonable to predict that blockade of Ca2+ entry through a single channel may not be capable of preventing the Ca2+ flood of cells by the uncontrolled Ca2+ entry. Furthermore, as Ca2+ signaling is involved in the regulation of myriad functions in different cell types, it seems also reasonable to guess that a therapy should be more efficient by targeting different cells with various drugs. Here, we propose to mitigate Ca2+ entry by the simultaneous partial blockade of three quite different subtypes of plasmalemmal calcium channels that is, the Cav1 subtype of VOCCs, the Orai1 store-operated calcium channel (SOCC), and the purinergic P2X7 calcium channel. All three channels are expressed in both microglia and neurons. Thus, by targeting the three channels with a combination of three drug blockers we expect favorable changes in some of the pathogenic features of NDDs, namely (i) to mitigate Ca2+ entry into microglia; (ii) to decrease the Ca2+-dependent microglia activation; (iii) to decrease the sustained neuroinflammation; (iv) to decrease the uncontrolled Ca2+ entry into neurons; (v) to rescue vulnerable neurons from death; and (vi) to delay disease progression. In this review we discuss the arguments underlying our triad hypothesis in the sense that the combination of three repositioned medicines targeting Cav1, Orai1, and P2X7 calcium channels could boost neuroprotection and delay the progression of AD and other NDDs.

A Non-Invasive and DNA-free Approach to Upregulate Mammalian Voltage-Gated Calcium Channels and Neuronal Calcium Signaling via Terahertz Stimulation

Mammalian voltage-gated calcium channels (CaV) play critical roles in cardiac excitability, synaptic transmission, and gene transcription. Dysfunctions in CaV are implicated in a variety of cardiac and neurodevelopmental disorders. Current pharmacological approaches to enhance CaV activity are limited by off-target effects, drug metabolism issues, cytotoxicity, and imprecise modulation. Additionally, genetically-encoded channel activators and optogenetic tools are restricted by gene delivery challenges and biosafety concerns. Here a novel terahertz (THz) wave-based method to upregulate CaV1.2, a key subtype of CaV, and boost CaV1-mediated Ca2+ signaling in neurons without introducing exogenous DNA is presented. Using molecular dynamics simulations, it is shown that 42.5 THz (7.05 µm, 1418 cm-1) waves enhance Ca2+ conductance in CaV1.2 by resonating with the stretching mode of the -COO- group in the selectivity filter. Electrophysiological recordings and Ca2+ imaging confirm that these waves rapidly, reversibly, and non-thermally increase calcium influx of CaV1.2 in HEK293 cells and induce acute Ca2+ signals in neurons. Furthermore, this irradiation upregulates critical CaV1 signals, including CREB phosphorylation and c-Fos expression, in vitro and in vivo, without raising significant biosafety risks. This DNA-free, non-invasive approach offers a promising approach for modulating CaV gating and Ca2+ signaling and treating diseases characterized by deficits in CaV functions.

Neuroprotective Effects of Ferrostatin and Necrostatin Against Entorhinal Amyloidopathy-Induced Electrophysiological Alterations Mediated by voltage-gated Ca2+ Channels in the Dentate Gyrus Granular Cells

Alzheimer's disease (AD) is a progressive neurodegenerative disease that is the main form of dementia. Abnormal deposition of amyloid-beta (Aβ) peptides in neurons and synapses cause neuronal loss and cognitive deficits. We have previously reported that ferroptosis and necroptosis were implicated in Aβ25-35 neurotoxicity, and their specific inhibitors had attenuating effects on cognitive impairment induced by Aβ25-35 neurotoxicity. Here, we aimed to examine the impact of ferroptosis and necroptosis inhibition following the Aβ25-35 neurotoxicity on the neuronal excitability of dentate gyrus (DG) and the possible involvement of voltage-gated Ca2+ channels in their effects. After inducing Aβ25-35 neurotoxicity, electrophysiological alterations in the intrinsic properties and excitability were recorded by the whole-cell patch-clamp under current-clamp condition. Voltage-clamp recordings were also performed to shed light on the involvement of calcium channel currents. Aβ25-35 neurotoxicity induced a considerable reduction in input resistance (Rin), accompanied by a profoundly decreased excitability and a reduction in the amplitude of voltage-gated calcium channel currents in the DG granule cells. However, three days of administration of either ferrostatin-1 (Fer-1), a ferroptosis inhibitor, or Necrostatin-1 (Nec-1), a necroptosis inhibitor, in the entorhinal cortex could almost preserve the normal excitability and the Ca2+ currents. In conclusion, these findings suggest that ferroptosis and necroptosis involvement in EC amyloidopathy could be a potential candidate to prevent the suppressive effect of Aβ on the Ca2+ channel current and neuronal function, which might take place in neurons during the development of AD.

Voltage-gated calcium channels in genetic epilepsies

Voltage-gated calcium channels (VGCC) are abundant in the central nervous system and serve a broad spectrum of functions, either directly in cellular excitability or indirectly to regulate Ca2+ homeostasis. Ca2+ ions act as one of the main connections in excitation-transcription coupling, muscle contraction and excitation-exocytosis coupling, including synaptic transmission. In recent years, many genes encoding VGCCs main α or additional auxiliary subunits have been associated with epilepsy. This review sums up the current state of knowledge on disease mechanisms and provides guidance on disease-specific therapies where applicable.

Too much of a good thing: The case of SOCE in cellular apoptosis

Intracellular calcium (Ca2+) is an essential second messenger in eukaryotic cells regulating numerous cellular functions such as contraction, secretion, immunity, growth, and metabolism. Ca2+ signaling is also a key signal transducer in the intrinsic apoptosis pathway. The store-operated Ca2+ entry pathway (SOCE) is ubiquitously expressed in eukaryotic cells, and is the primary Ca2+ influx pathway in non-excitable cells. SOCE is mediated by the endoplasmic reticulum Ca2+ sensing STIM proteins, and the plasma membrane Ca2+-selective Orai channels. A growing number of studies have implicated SOCE in regulating cell death primarily via the intrinsic apoptotic pathway in a variety of tissues and in response to physiological stressors such as traumatic brain injury, ischemia reperfusion injury, sepsis, and alcohol toxicity. Notably, the literature points to excessive cytosolic Ca2+ influx through SOCE in vulnerable cells as a key factor tipping the balance towards cellular apoptosis. While the literature primarily addresses the functions of STIM1 and Orai1, STIM2, Orai2 and Orai3 are also emerging as potential regulators of cell death. Here, we review the functions of STIM and Orai proteins in regulating cell death and the implications of this regulation to human pathologies.

The Role of Voltage-Gated Calcium Channels in Basal Ganglia Neurodegenerative Disorders

Calcium (Ca2+) plays a central role in regulating many cellular processes and influences cell survival. Several mechanisms can disrupt Ca2+ homeostasis to trigger cell death, including oxidative stress, mitochondrial damage, excitotoxicity, neuroinflammation, autophagy, and apoptosis. Voltage-gated Ca2+ channels (VGCCs) act as the main source of Ca2+ entry into electrically excitable cells, such as neurons, and they are also expressed in glial cells such as astrocytes and oligodendrocytes. The dysregulation of VGCC activity has been reported in both Parkinson's disease (PD) and Huntington's (HD). PD and HD are progressive neurodegenerative disorders (NDs) of the basal ganglia characterized by motor impairment as well as cognitive and psychiatric dysfunctions. This review will examine the putative role of neuronal VGCCs in the pathogenesis and treatment of central movement disorders, focusing on PD and HD. The link between basal ganglia disorders and VGCC physiology will provide a framework for understanding the neurodegenerative processes that occur in PD and HD, as well as a possible path towards identifying new therapeutic targets for the treatment of these debilitating disorders.

Molecular mechanisms underlying activity-dependent ischemic tolerance in the brain

Ischemic stroke is one of the leading causes of death and disability worldwide. The inhibition of cerebral blood flow triggers intertwined pathological events, resulting in cell death and loss of brain function. Interestingly, animals pre-exposed to short-term ischemia can tolerate subsequent severe ischemia. This phenomenon is called ischemic tolerance and is also triggered by other noxious stimuli. However, whether short-term exposure to non-noxious stimuli can induce ischemic tolerance remains unknown. Recently, we found that pre-exposing mice to an enriched environment for 40 min is sufficient to facilitate cell survival after a subsequent stroke. The neuroprotective process depends on the neuronal activity soon before stroke, of which the activity-dependent transcription factor Npas4 is essential. Excessive Ca²⁺ influx triggers Npas4 expression in ischemic neurons, leading to the activation of neuroprotective programs. Pre-induction of Npas4 in the normal brain effectively supports cell survival after stroke. Furthermore, our study revealed that Npas4 regulates L-type voltage-gated Ca²⁺ channels through expression of the small Ras-like GTPase Gem in ischemic neurons. Ischemic tolerance is a good model for understanding how to promote neuroprotective mechanisms in the normal and injured brain. Here, we highlight activity-dependent ischemic tolerance and discuss its role in promoting neuroprotection against stroke.

Cytotoxicity Models in Chromaffin Cells to Evaluate Neuroprotective Compounds

Primary cultures of bovine chromaffin cells are considered a good model to evaluate potential neuroprotective compounds for two major reasons: (i) they share many common features to neurons as they synthesize, store, and release neurotransmitters; they are excitable cells that express voltage-dependent calcium, potassium, and sodium channels; they express different neuronal receptor subtypes; and (ii) they can be easily cultured in high quantities from adult animals; as adult para-neurons, they can be used to reproduce different neurodegenerative-like cytotoxicity models. In this chapter, we describe protocols to mimic calcium overload (veratridine and thapsigargin) and oxidative stress (rotenone plus oligomycin-A and 6-hydroxydopamine) to evaluate potential neuroprotective compounds.

TGF-β1 Protects Trauma-injured Murine Cortical Neurons by Upregulating L-type Calcium Channel Cav1.2 via the p38 Pathway

Traumatic brain injury (TBI) is a leading cause of disability and death in adolescents, and there is a lack of effective methods of treatment. The neuroprotective effects exerted by TGF-β1 can ameliorate a range of neuronal lesions in multiple central nervous system diseases. In this study, we used an in-vitro TBI model of mechanical injury on murine primary cortical neurons and the neuro-2a cell line to investigate the neuroprotective role played by TGF-β1 in cortical neurons in TBI. Our results showed that TGF-β1 significantly increased neuronal viability and inhibited apoptosis for 24 h after trauma. The expression of Ca_v1.2, an L-type calcium channel (LTCC) isoform, decreased significantly after trauma injury, and this change was reversed by TGF-β1. Nimodipine, a classic LTCC blocker, abolished the protective effect of TGF-β1 on trauma-induced neuronal apoptosis. The knockdown of Ca_v1.2 in differentiated neuro-2a cells significantly inhibited the anti-apoptosis effect of TGF-β1 exerted on injured neuro-2a cells. Moreover, TGF-β1 rescued and enhanced the trauma-suppressed neuro-2a intracellular Ca²⁺ concentration, while the effect of TGF-β1 was partially inhibited by nimodipine. TGF-β1 significantly upregulated the expression of Ca_v1.2 by activating the p38 MAPK pathway and by inhibiting trauma-induced neuronal apoptosis. In conclusion, TGF-β1 increased trauma-injured murine cortical neuronal activity and inhibited apoptosis by upregulating Cav1.2 channels via activating the p38 MAPK pathway. Therefore, the TGF-β1/p38 MAPK/Ca_v 1.2 pathway has the potential to be used as a novel therapeutic target for TBI.

Therapeutical interference with the epigenetic landscape of germ cell tumors: a comparative drug study and new mechanistical insights

Background

Type II germ cell tumors (GCT) are the most common solid cancers in males of age 15 to 35 years. Treatment of these tumors includes cisplatin-based therapy achieving high cure rates, but also leading to late toxicities. As mainly young men are suffering from GCTs, late toxicities play a major role regarding life expectancy, and the development of therapy resistance emphasizes the need for alternative therapeutic options. GCTs are highly susceptible to interference with the epigenetic landscape; therefore, this study focuses on screening of drugs against epigenetic factors as a treatment option for GCTs.

Results

We present seven different epigenetic inhibitors efficiently decreasing cell viability in GCT cell lines including cisplatin-resistant subclones at low concentrations by targeting epigenetic modifiers and interactors, like histone deacetylases (Quisinostat), histone demethylases (JIB-04), histone methyltransferases (Chaetocin), epigenetic readers (MZ-1, LP99) and polycomb-repressive complexes (PRT4165, GSK343). Mass spectrometry-based analyses of the histone modification landscape revealed effects beyond the expected mode-of-action of each drug, suggesting a wider spectrum of activity than initially assumed. Moreover, we characterized the effects of each drug on the transcriptome of GCT cells by RNA sequencing and found common deregulations in gene expression of ion transporters and DNA-binding factors. A kinase array revealed deregulations of signaling pathways, like cAMP, JAK-STAT and WNT.

Conclusion

Our study identified seven drugs against epigenetic modifiers to treat cisplatin-resistant GCTs. Further, we extensively analyzed off-target effects and modes-of-action, which are important for risk assessment of the individual drugs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01223-1.

Calcium dysregulation and compensation in cortical pyramidal neurons of the R6/2 mouse model of Huntington's disease

Huntington's disease (HD) is a fatal, hereditary neurodegenerative disorder that predominantly affects striatal medium-sized spiny neurons and cortical pyramidal neurons (CPNs). It has been proposed that perturbations in Ca²⁺ homeostasis could play a role in CPN alterations. To test this hypothesis, we used the R6/2 mouse model of juvenile HD at different stages of disease progression; presymptomatic, early symptomatic, and late symptomatic. We combined whole-cell patch-clamp recordings of layer 2/3 CPNs with two-photon laser scanning microscopy to image somatic and dendritic Ca²⁺ transients associated with evoked action potentials (APs). We found that the amplitude of AP-induced Ca²⁺ transients recorded at the somata of CPNs was significantly reduced in presymptomatic and late symptomatic R6/2 mice compared with wild-type (WT) littermates. However, reduced amplitudes were compensated by increases in decay times, so that Ca²⁺ transient areas were similar between genotypes. AP-induced Ca²⁺ transients in CPN proximal dendrites were variable and differences did not reach statistical significance, except for reduced areas in the late symptomatic group. In late symptomatic mice, a specific store-operated Ca²⁺ channel antagonist, EVP4593, reduced somatic Ca²⁺ transient amplitude similarly in WT and R6/2 CPNs. In contrast, dantrolene, a ryanodine receptor (RyR) antagonist, and nifedipine, an L-type Ca²⁺ channel blocker, significantly reduced both somatic Ca²⁺ transient amplitude and area in R6/2 but not WT CPNs. These findings demonstrate that perturbations of Ca²⁺ homeostasis and compensation occur in CPNs before and after the onset of overt symptoms, and suggest RyRs and L-type Ca²⁺ channels as potential targets for therapeutic intervention.NEW & NOTEWORTHY We used two-photon microscopy to examine calcium influx induced by action potentials in cortical pyramidal neurons from a mouse model of Huntington's disease (HD), the R6/2. The amplitude of somatic calcium transients was reduced in R6/2 mice compared with controls. This reduction was compensated by increased decay times, which could lead to reduced calcium buffering capacity. L-type calcium channel and ryanodine receptor blockers reduced calcium transient area in HD neurons, suggesting new therapeutic avenues.

Ras-like Gem GTPase induced by Npas4 promotes activity-dependent neuronal tolerance for ischemic stroke

Ischemic stroke, which results in loss of neurological function, initiates a complex cascade of pathological events in the brain, largely driven by excitotoxic Ca2+ influx in neurons. This leads to cortical spreading depolarization, which induces expression of genes involved in both neuronal death and survival; yet, the functions of these genes remain poorly understood. Here, we profiled gene expression changes that are common to ischemia (modeled by middle cerebral artery occlusion [MCAO]) and to experience-dependent activation (modeled by exposure to an enriched environment [EE]), which also induces Ca2+ transients that trigger transcriptional programs. We found that the activity-dependent transcription factor Npas4 was up-regulated under MCAO and EE conditions and that transient activation of cortical neurons in the healthy brain by the EE decreased cell death after stroke. Furthermore, both MCAO in vivo and oxygen-glucose deprivation in vitro revealed that Npas4 is necessary and sufficient for neuroprotection. We also found that this protection involves the inhibition of L-type voltage-gated Ca2+ channels (VGCCs). Next, our systematic search for Npas4-downstream genes identified Gem, which encodes a Ras-related small GTPase that mediates neuroprotective effects of Npas4. Gem suppresses the membrane localization of L-type VGCCs to inhibit excess Ca2+ influx, thereby protecting neurons from excitotoxic death after in vitro and in vivo ischemia. Collectively, our findings indicate that Gem expression via Npas4 is necessary and sufficient to promote neuroprotection in the injured brain. Importantly, Gem is also induced in human cerebral organoids cultured under an ischemic condition, revealing Gem as a new target for drug discovery.

Phytochemical Analysis and Evaluation of Biological Activity of Lawsonia inermis Seeds Related to Alzheimer's Disease

Using Lawsonia inermis L. (henna) seeds has been frequently recommended for the improvement of memory in Iranian Traditional Medicine (ITM). In this respect, different fractions of the plant were prepared and evaluated for their in vitro biological assays related to Alzheimer's disease (AD), including acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activity as well as metal chelating ability and DPPH antioxidant activity. The dichloromethane and ethyl acetate fractions were able to inhibit the BChE selectively with IC₅₀ values of 113.47 and 124.90 μg/mL, respectively, compared with donepezil as the reference drug (IC₅₀ = 1.52 μg/mL). However, all fractions were inactive toward AChE. Phytochemical analysis of the dichloromethane fraction indicated the presence of β-sitosterol (1), 3-O-β-acetyloleanolic acid (2), 3-O-(Z)-coumaroyl oleanolic acid (3), betulinic acid (4), and oleanolic acid (5). The inhibitory activity of isolated compounds was also evaluated toward AChE and BChE. Among them, compounds 2 and 5 showed potent inhibitory activity toward BChE with IC₅₀ values of 77.13 and 72.20 μM, respectively. However, all compounds were inactive toward AChE. Moreover, molecular docking study confirmed desired interactions between those compounds and the BChE active site. The ability of fractions and compounds to chelate biometals (Cu²⁺, Fe²⁺, and Zn²⁺) was also investigated. Finally, DPPH antioxidant assay revealed that the ethyl acetate (IC₅₀ = 3.08 μg/mL) and methanol (IC₅₀ = 3.64 μg/mL) fractions possessed excellent antioxidant activity in comparison to BHA as the positive control (IC₅₀ = 3.79 μg/mL).

Sevoflurane increases intracellular calcium to induce mitochondrial injury and neuroapoptosis

Sevoflurane is commonly used in clinical anesthesia. However, some reports indicated that Sevoflurane could induce mitochondrial injury and neuroapoptosis. Although the mechanism remains unclear, evidence points to the increase of intracellular calcium after administration of Sevoflurane. Herein, we sought whether the increment of intracellular Ca2+ caused by Sevoflurane administration could induce mitochondrial injury and apoptosis in primary neurons of the hippocampus. Fluo-4-acetoxymethyl ester Ca2+ probe was used for measuring intracellular Ca2+ concentrations. LDH assay, CCK-8 assay, and Western blotting were performed to confirm Sevoflurane-induced neuroapoptosis. ROS, mPTP, and ATP production were assayed to reveal mitochondrial injury. Our results indicated that Sevoflurane increased intracellular Ca2+ and neuronal death. Sevoflurane also elevated ROS and the opening of mPTP, and decreased ATP production in neurons. The expression of cytochrome c, cleaved caspase-9, cleaved caspase-3, and the ratio of Bax/Bcl-2 were also increased. By using calcium channel blocker Nimodipine, the increase of intracellular Ca2+ was attenuated, and the death rate of neurons, the ROS and opening of mPTP, decreased ATP production, the expressions of cytochrome c, cleaved caspase-9, cleaved caspase-3 and the ratio of Bax/Bcl-2 were alleviated. Our study suggested that Sevoflurane could increase intracellular Ca2+ to induce mitochondrial injury and mitochondria-mediated neuroapoptosis in neurons.

P2X7 Receptor Antagonism as a Potential Therapy in Amyotrophic Lateral Sclerosis

This review focuses on the purinergic ionotropic receptor P2X7 (P2X7R) as a potential target for developing drugs that delay the onset and/or disease progression in patients with amyotrophic lateral sclerosis (ALS). Description of clinical and genetic ALS features is followed by an analysis of advantages and drawbacks of transgenic mouse models of disease based on mutations in a bunch of proteins, particularly Cu/Zn superoxide dismutase (SOD1), TAR-DNA binding protein-43 (TDP-43), Fused in Sarcoma/Translocated in Sarcoma (FUS), and Chromosome 9 open reading frame 72 (C9orf72). Though of limited value, these models are however critical to study the proof of concept of new compounds, before reaching clinical trials. The authors also provide a description of ALS pathogenesis including protein aggregation, calcium-dependent excitotoxicity, dysfunction of calcium-binding proteins, ultrastructural mitochondrial alterations, disruption of mitochondrial calcium handling, and overproduction of reactive oxygen species (ROS). Understanding disease pathogenic pathways may ease the identification of new drug targets. Subsequently, neuroinflammation linked with P2X7Rs in ALS pathogenesis is described in order to understand the rationale of placing the use of P2X7R antagonists as a new therapeutic pharmacological approach to ALS. This is the basis for the hypothesis that a P2X7R blocker could mitigate the neuroinflammatory state, indirectly leading to neuroprotection and higher motoneuron survival in ALS patients.

Calcium Entry through TRPV1: A Potential Target for the Regulation of Proliferation and Apoptosis in Cancerous and Healthy Cells

Intracellular calcium (Ca2+) concentration ([Ca2+]i) is a key determinant of cell fate and is implicated in carcinogenesis. Membrane ion channels are structures through which ions enter or exit the cell, depending on the driving forces. The opening of transient receptor potential vanilloid 1 (TRPV1) ligand-gated ion channels facilitates transmembrane Ca2+ and Na+ entry, which modifies the delicate balance between apoptotic and proliferative signaling pathways. Proliferation is upregulated through two mechanisms: (1) ATP binding to the G-protein-coupled receptor P2Y2, commencing a kinase signaling cascade that activates the serine-threonine kinase Akt, and (2) the transactivation of the epidermal growth factor receptor (EGFR), leading to a series of protein signals that activate the extracellular signal-regulated kinases (ERK) 1/2. The TRPV1-apoptosis pathway involves Ca2+ influx and efflux between the cytosol, mitochondria, and endoplasmic reticulum (ER), the release of apoptosis-inducing factor (AIF) and cytochrome c from the mitochondria, caspase activation, and DNA fragmentation and condensation. While proliferative mechanisms are typically upregulated in cancerous tissues, shifting the balance to favor apoptosis could support anti-cancer therapies. TRPV1, through [Ca2+]i signaling, influences cancer cell fate; therefore, the modulation of the TRPV1-enforced proliferation-apoptosis balance is a promising avenue in developing anti-cancer therapies and overcoming cancer drug resistance. As such, this review characterizes and evaluates the role of TRPV1 in cell death and survival, in the interest of identifying mechanistic targets for drug discovery.

Alterations of Calcium Channels in a Mouse Model of Huntington's Disease and Neuroprotection by Blockage of CaV1 Channels

Huntington’s disease (HD) is a neurodegenerative autosomal dominant disorder, characterized by symptoms of involuntary movement of the body, loss of cognitive function, psychiatric disorder, leading inevitably to death. It has been previously described that higher levels of brain expression of Cav1 channels are involved in major neurodegenerative disorders, such as Alzheimer’s disease and Parkinson’s disease. Our results demonstrate that a bacterial artificial chromosome (BAC)-mediated transgenic mouse model (BACHD mice) at the age of 3 and 12 months exhibits significantly increased Cav1.2 protein levels in the cortex, as compared with wild-type littermates. Importantly, electrophysiological analyses confirm a significant increase in L-type Ca2+ currents and total Ca2+ current density in cortical neurons from BACHD mice. By using an in vitro assay to measure neuronal cell death, we were able to observe neuronal protection against glutamate toxicity after treatment with Cav1 blockers, in wild-type and, more importantly, in BACHD neurons. According to our data, Cav1 blockers may offer an interesting strategy for the treatment of HD. Altogether, our results show that mutant huntingtin (mHtt) expression may cause a dysregulation of Cav1.2 channels and we hypothesize that this contributes to neurodegeneration during HD.

L-type Ca2+ channel-mediated Ca2+ influx adjusts neuronal mitochondrial function to physiological and pathophysiological conditions

L-type voltage-gated Ca2+ channels (LTCCs) are implicated in neurodegenerative processes and cell death. Accordingly, LTCC antagonists have been proposed to be neuroprotective, although this view is disputed, because intentional LTCC activation can also have beneficial effects. LTCC-mediated Ca2+ influx influences mitochondrial function, which plays a crucial role in the regulation of cell viability. Hence, we investigated the effect of modulating LTCC-mediated Ca2+ influx on mitochondrial function in cultured hippocampal neurons. To activate LTCCs, neuronal activity was stimulated by increasing extracellular K+ or by application of the GABAA receptor antagonist bicuculline. The activity of LTCCs was altered by application of an agonistic (Bay K8644) or an antagonistic (isradipine) dihydropyridine. Our results demonstrated that activation of LTCC-mediated Ca2+ influx affected mitochondrial function in a bimodal manner. At moderate stimulation strength, ATP synthase activity was enhanced, an effect that involved Ca2+-induced Ca2+ release from intracellular stores. In contrast, high LTCC-mediated Ca2+ loads led to a switch in ATP synthase activity to reverse-mode operation. This effect, which required nitric oxide, helped to prevent mitochondrial depolarization and sustained increases in mitochondrial Ca2+ Our findings indicate a complex role of LTCC-mediated Ca2+ influx in the tuning and maintenance of mitochondrial function. Therefore, the use of LTCC inhibitors to protect neurons from neurodegeneration should be reconsidered carefully.

The T-type Ca2+ Channel Cav3.2 Regulates Differentiation of Neural Progenitor Cells during Cortical Development via Caspase-3

Here we report that the low-voltage-dependent T-type calcium (Ca²⁺) channel Ca_v3.2, encoded by the CACNA1H gene, regulates neuronal differentiation during early embryonic brain development through activating caspase-3. At the onset of neuronal differentiation, neural progenitor cells exhibited spontaneous Ca²⁺ activity. This activity strongly correlated with the upregulation of CACNA1H mRNA. Cells exhibiting robust spontaneous Ca²⁺ signaling had increased caspase-3 activity unrelated to apoptosis. Inhibition of Ca_v3.2 by drugs or viral CACNA1H knock down resulted in decreased caspase-3 activity followed by suppressed neurogenesis. In contrast, when CACNA1H was overexpressed, increased neurogenesis was detected. Cortical slices from Cacna1h knockout mice showed decreased spontaneous Ca²⁺ activity, a significantly lower protein level of cleaved caspase-3, and microanatomical abnormalities in the subventricular/ventricular and cortical plate zones when compared to their respective embryonic controls. In summary, we demonstrate a novel relationship between Ca_v3.2 and caspase-3 signaling that affects neurogenesis in the developing brain.

Intracellular emetic signaling evoked by the L-type Ca2+ channel agonist FPL64176 in the least shrew (Cryptotis parva)

Ca²⁺ plays a major role in maintaining cellular homeostasis and regulates processes including apoptotic cell death and side-effects of cancer chemotherapy including vomiting. Currently we explored the emetic mechanisms of FPL64176, an L-type Ca²⁺ channel (LTCC) agonist with maximal emetogenic effect at its 10 mg/kg dose. FPL64176 evoked c-Fos immunoreactivity in shrew brainstem sections containing the vomit-associated nuclei, nucleus tractus solitarius (NTS) and dorsal motor nucleus of the vagus. FPL64176 also increased phosphorylation of proteins ERK1/2, PKCα/βII and Akt in the brainstem. Moreover, their corresponding inhibitors (PD98059, GF 109203X and LY294002, respectively) reduced FPL64176-evoked vomiting. A 30 min subcutaneous (s.c.) pretreatment with the LTCC antagonist nifedipine (10 mg/kg) abolished FPL64176-elicited vomiting, c-Fos expression, and emetic effector phosphorylation. Ryanodine receptors (RyRs) and inositol trisphosphate receptors (IP₃Rs) mediate intracellular Ca²⁺ release from the sarcoplasmic/endoplasmic reticulum. The RyR antagonist dantrolene (i.p.), or a combination of low doses of nifedipine and dantrolene, but not the IP₃R antagonist 2-APB, significantly attenuated FPL64176-induced vomiting. The serotonin type 3 receptor (5-HT₃R) antagonist palonosetron (s.c.), the neurokinin 1 receptor (NK₁R) antagonist netupitant (i.p.) or a combination of non-effective doses of netupitant and palonosetron showed antiemetic potential against FPL64176-evoked vomiting. Serotonin (5-HT) and substance P immunostaining revealed FPL64176-induced emesis was accompanied by an increase in 5-HT but not SP-immunoreactivity in the dorsomedial subdivision of the NTS. These findings demonstrate that Ca²⁺ mobilization through LTCCs and RyRs, and subsequent emetic effector phosphorylation and 5-HT release play important roles in FPL64176-induced emesis which can be prevented by 5-HT₃R and NK₁R antagonists.

Tacripyrimidines, the first tacrine-dihydropyrimidine hybrids, as multi-target-directed ligands for Alzheimer's disease

Notwithstanding the combination of cholinesterase (ChE) inhibition and calcium channel blockade within a multitarget therapeutic approach is envisaged as potentially beneficial to confront Alzheimer's disease (AD), this strategy has been scarcely investigated. To explore this promising line, a series of 5-amino-4-aryl-3,4,6,7,8,9-hexahydropyrimido [4,5-b]quinoline-2(1H)-thiones (tacripyrimidines) (4a-l) were designed by juxtaposition of tacrine, a ChE inhibitor (ChEI), and 3,4-dihydropyrimidin-2(1H)-thiones, as efficient calcium channel blockers (CCBs). In agreement with their design, all tacripyrimidines, except the unsubstituted parent compound and its p-methoxy derivative, acted as moderate to potent CCBs with activities generally similar or higher than the reference CCB drug nimodipine and were modest-to-good ChEIs. Most interestingly, the 3'-methoxy derivative (4e) emerged as the first well balanced ChEI/CCB agent, acting as low micromolar hChEI (3.05 μM and 3.19 μM on hAChE and hBuChE, respectively) and moderate CCB (30.4% at 1 μM) with no significant hepatotoxicity toward HepG2 cells and good predicted oral absorption and blood brain barrier permeability.

Critical role of angiotensin II type 2 receptors in the control of mitochondrial and cardiac function in angiotensin II-preconditioned rat hearts

Angiotensin II preconditioning (APC) involves an angiotensin II type 1 receptor (AT1-R)-dependent translocation of PKCε and survival kinases to the mitochondria leading to cardioprotection after ischemia-reperfusion (IR). However, the role that mitochondrial AT1-Rs and angiotensin II type 2 receptors (AT2-Rs) play in APC is unknown. We investigated whether pretreatment of Langendorff-perfused rat hearts with losartan (L, AT1-R blocker), PD 123,319 (PD, AT2-R blocker), or their combination (L + PD) affects mitochondrial AT1-R, AT2-R, PKCε, PKCδ, Akt, PKG-1, MAPKs (ERK1/2, JNK, p38), mitochondrial respiration, cardiac function, and infarct size (IS). The results indicate that expression of mitochondrial AT1-Rs and AT2-Rs were enhanced by APC 1.91-fold and 2.32-fold, respectively. Expression of AT2-R was abolished by PD but not by L, whereas the AT1-R levels were abrogated by both blockers. The AT1-R response profile to L and PD was also shared by PKCε, Akt, MAPKs, and PKG-1, but not by PKCδ. A marked increase in state 3 (1.84-fold) and respiratory control index (1.86-fold) of mitochondria was observed with PD regardless of L treatment. PD also enhanced the post-ischemic recovery of rate pressure product (RPP) by 74% (p < 0.05) compared with APC alone. Losartan, however, inhibited the (RPP) by 44% (p < 0.05) before IR and reduced the APC-induced increase of post-ischemic cardiac recovery by 73% (p < 0.05). Finally, L enhanced the reduction of IS by APC through a PD-sensitive mechanism. These findings suggest that APC upregulates angiotensin II receptors in mitochondria and that AT2-Rs are cardioprotective through their permissive action on AT1-R signaling and the suppression of cardiac function.

Neurotransmitters in the mediation of cerebral ischemic injury

Under physiological conditions, neurotransmitters shape neuronal networks and control several cellular and synaptic functions. In the mammalian central nervous system (CNS), excitatory and inhibitory neurotransmission are mediated in large part by glutamate and gamma-aminobutyric acid (GABA), which are excitatory and inhibitory neurotransmitters, respectively. Glutamate and GABA also play crucial roles in neurological disorders such as cerebral ischemia. Glutamate in particular causes excitotoxicity, known as one of the hallmark mechanisms in the pathophysiology of cerebral ischemic injury for more than thirty years. Excitotoxicity occurs due to excessive glutamate release leading to overactivation of postsynaptic glutamate receptors, which evokes a downstream cascade that eventually leads to neuronal dysfunction and degeneration. Also, a reduction in GABA receptor response after ischemia impedes these inhibitory effectors from attenuating excitotoxicity and thereby further enabling the excitotoxic insult. This review focuses on the mechanisms by which glutamate and GABA mediate excitotoxicity and ischemic injury. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

Chromaffin cells as a model to evaluate mechanisms of cell death and neuroprotective compounds

In this review, we show how chromaffin cells have contributed to evaluate neuroprotective compounds with diverse mechanisms of action. Chromaffin cells are considered paraneurons, as they share many common features with neurons: (i) they synthesize, store, and release neurotransmitters upon stimulation and (ii) they express voltage-dependent calcium, sodium, and potassium channels, in addition to a wide variety of receptors. All these characteristics, together with the fact that primary cultures from bovine adrenal glands or chromaffin cells from the tumor pheochromocytoma cell line PC12 are easy to culture, make them an ideal model to study neurotoxic mechanisms and neuroprotective drugs. In the first part of this review, we will analyze the different cytotoxicity models related to calcium dyshomeostasis and neurodegenerative disorders like Alzheimer's or Parkinson's. Along the second part of the review, we describe how different classes of drugs have been evaluated in chromaffin cells to determine their neuroprotective profile in different neurodegenerative-related models.

Differential Somatic Ca2+ Channel Profile in Midbrain Dopaminergic Neurons

Dopaminergic (DA) neurons located in the ventral midbrain continuously generate a slow endogenous pacemaker activity, the mechanism of which is still debated. It has been suggested that, in the substantia nigra pars compacta (SNc), the pacemaking relies more on Ca(2+) channels and that the density of L-type Ca(2+) channels is higher in these DA neurons than in those located in the ventral tegmental area (VTA). This might lead to a higher Ca(2+) load in SNc DA neurons and explain their higher susceptibility to degeneration. However, direct evidence for this hypothesis is lacking. We found that the L-type current and channel density are indeed higher in the somata of rat SNc DA neurons and that this current undergoes less inactivation in this region. Nonstationary fluctuation analysis measurements showed a much higher number of L-type channels in the soma of SNc DA neurons, as well as a smaller single-channel conductance, pointing to a possible different molecular identity of L-type channels in DA neurons from the two areas. A major consequence of this is that pacemaking and, even more so, bursting are associated with a larger Ca(2+) entry through L-type channels in SNc DA neurons than in their VTA counterparts. Our results establish a molecular and functional difference between two populations of midbrain DA neurons that may contribute to their differential sensitivity to neurodegeneration.

SIGNIFICANCE STATEMENT

Dopamine neurons from the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) are involved in various brain functions, such as movement initiation and goal directed behavior, respectively. This work shows that, although both neurons fire in a similar regular and slow pacemaker mode, this firing activity is supported by different calcium channel landscapes. Indeed, the L-type calcium current is larger in the soma of dopamine neurons of the SNc, leading to a higher charge transfer through L-type channels during pacemaking and bursting. Therefore, these neurons may be physiologically exposed to a larger stress than their neighbors from the VTA.

Comparative Transcriptomics of Buzura suppressaria (Lepidoptera: Geometridae) Assembled De Novo Yield Insights Into Response After Buzura suppressaria Nuclear Polyhedrosis Virus Infection

Buzura suppressaria Guenee (Lepidoptera: Geometridae) is a defoliator that seriously harms eucalyptus trees in South China. Buzura suppressaria nuclear polyhedrosis virus (BsNPV) is a baculovirus that infects B. suppressaria with high specificity and efficiency. Transcriptomes of B. suppressaria were sequenced before and after BsNPV infection using an Illumina-based platform to probe for differentially expressed genes (DEGs) of B. suppressaria after viral infection. On average, ∼57.4 million high-quality clean reads were generated and assembled de novo into 69,761 unigenes. The NCBI nonredundant protein, Swiss-Prot, Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene ontology (GO), and Cluster of Orthologous Groups databases were used to annotate unigenes through NCBI BLAST; 33,575 unigenes (48.1%) were then mapped to at least one of these databases, and 4,366 unigenes (6.3%) were mapped to all databases. Differential expression analysis showed that 25,212 unigenes were upregulated and 22,880 unigenes were downregulated in at least one pairwise comparison. Control versus 48 h had more DEGs than other two pairwise comparisons in either the GO or KEGG database, because the number of regulated gene would increase as BsNPV infected more tissues and would decrease as more tissues were disabled. To ascertain B. suppressaria immune response to BsNPV infection, DEGs were annotated to the GO and KEGG databases. In total, 89 GO categories are related to immune response and 1,007 DEGs are annotated to these GO categories. Furthermore, 7 downregulated DEGs and 37 upregulated were obtained simultaneously in all three groups. These DEGs were considered to possess a central role throughout viral infection.

A review on tacrine-based scaffolds as multi-target drugs (MTDLs) for Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial neurological disorder among elderly people and combinatorial factors such as genetic, lifestyle, and environmental are involved in onset and disease progression. It has been demonstrated that loss of cholinergic transmission is one of the most significant causes of AD. One strategy currently being investigated for the development of new therapeutics relates to the enhancement of cholinergic system through several ways. At this juncture, anticholinesterase inhibitors have absorbed lots of attention and different marketed drugs such as donepezil, rivastigmine, tacrine, and galantamine have been developed. 9-Amino-1,2,3,4-tetrahydroacridine known as tacrine was introduced in 1945 as an efficient anticholinesterase agent. The mechanism of action of tacrine was proved to inhibit the metabolism of acetylcholine and therefore extending its activity and raising levels in the cerebral cortex. However, extensive use of tacrine was limited since it showed various side effects and toxicity. Thus, lots of efforts were carried out to prepare tacrine analogues to overcome the related adverse effects. This review describes differently synthesized tacrine-based scaffolds as cholinesterase inhibitors to manage Alzheimer's disease (AD).

Central Nervous System-Toxic Lidocaine Concentrations Unmask L-Type Ca²⁺ Current-Mediated Action Potentials in Rat Thalamocortical Neurons: An In Vitro Mechanism of Action Study

BACKGROUND

High systemic lidocaine concentrations exert well-known toxic effects on the central nervous system (CNS), including seizures, coma, and death. The underlying mechanisms are still largely obscure, and the actions of lidocaine on supraspinal neurons have received comparatively little study. We recently found that lidocaine at clinically neurotoxic concentrations increases excitability mediated by Na-independent, high-threshold (HT) action potential spikes in rat thalamocortical neurons. Our goal in this study was to characterize these spikes and test the hypothesis that they are generated by HT Ca currents, previously implicated in neurotoxicity. We also sought to identify and isolate the specific underlying subtype of Ca current.

METHODS

We investigated the actions of lidocaine in the CNS-toxic concentration range (100 μM-1 mM) on ventrobasal thalamocortical neurons in rat brain slices in vitro, using whole-cell patch-clamp recordings aided by differential interference contrast infrared videomicroscopy. Drugs were bath applied; action potentials were generated using current clamp protocols, and underlying currents were identified and isolated with ion channel blockers and electrolyte substitution.

RESULTS

Lidocaine (100 μM-1 mM) abolished Na-dependent tonic firing in all neurons tested (n = 46). However, in 39 of 46 (85%) neurons, lidocaine unmasked evoked HT action potentials with lower amplitudes and rates of de-/repolarization compared with control. These HT action potentials remained during the application of tetrodotoxin (600 nM), were blocked by Cd (50 μM), and disappeared after superfusion with an extracellular solution deprived of Ca. These features implied that the unmasked potentials were generated by high-voltage-activated Ca channels and not by Na channels. Application of the L-type Ca channel blocker, nifedipine (5 μM), completely blocked the HT potentials, whereas the N-type Ca channel blocker, ω-conotoxin GVIA (1 μM), had little effect.

CONCLUSIONS

At clinically CNS-toxic concentrations, lidocaine unmasked in thalamocortical neurons evoked HT action potentials mediated by the L-type Ca current while substantially suppressing Na-dependent excitability. On the basis of the known role of an increase in intracellular Ca in the pathogenesis of local anesthetic neurotoxicity, this novel action represents a plausible contributing candidate mechanism for lidocaine's CNS toxicity in vivo.

CNTF-ACM promotes mitochondrial respiration and oxidative stress in cortical neurons through upregulating L-type calcium channel activity

A specialized culture medium termed ciliary neurotrophic factor-treated astrocyte-conditioned medium (CNTF-ACM) allows investigators to assess the peripheral effects of CNTF-induced activated astrocytes upon cultured neurons. CNTF-ACM has been shown to upregulate neuronal L-type calcium channel current activity, which has been previously linked to changes in mitochondrial respiration and oxidative stress. Therefore, the aim of this study was to evaluate CNTF-ACM's effects upon mitochondrial respiration and oxidative stress in rat cortical neurons. Cortical neurons, CNTF-ACM, and untreated control astrocyte-conditioned medium (UC-ACM) were prepared from neonatal Sprague-Dawley rat cortical tissue. Neurons were cultured in either CNTF-ACM or UC-ACM for a 48-h period. Changes in the following parameters before and after treatment with the L-type calcium channel blocker isradipine were assessed: (i) intracellular calcium levels, (ii) mitochondrial membrane potential (ΔΨm), (iii) oxygen consumption rate (OCR) and adenosine triphosphate (ATP) formation, (iv) intracellular nitric oxide (NO) levels, (v) mitochondrial reactive oxygen species (ROS) production, and (vi) susceptibility to the mitochondrial complex I toxin rotenone. CNTF-ACM neurons displayed the following significant changes relative to UC-ACM neurons: (i) increased intracellular calcium levels (p < 0.05), (ii) elevation in ΔΨm (p < 0.05), (iii) increased OCR and ATP formation (p < 0.05), (iv) increased intracellular NO levels (p < 0.05), (v) increased mitochondrial ROS production (p < 0.05), and (vi) increased susceptibility to rotenone (p < 0.05). Treatment with isradipine was able to partially rescue these negative effects of CNTF-ACM (p < 0.05). CNTF-ACM promotes mitochondrial respiration and oxidative stress in cortical neurons through elevating L-type calcium channel activity.

Increased regucalcin gene expression extends survival in breast cancer patients: Overexpression of regucalcin suppresses the proliferation and metastatic bone activity in MDA-MB-231 human breast cancer cells in vitro

Human breast cancer is highly metastatic to bone and drives bone turnover. Breast cancer metastases cause osteolytic lesions and skeletal damage that leads to bone fractures. Regucalcin, which plays a pivotal role as an inhibitor of signal transduction and transcription activity, has been suggested to act as a suppressor of human cancer. In the present study, we compared the clinical outcome between 44 breast cancer patients with higher regucalcin expression and 43 patients with lower regucalcin expression. Prolonged relapse-free survival was identified in the patients with increased regucalcin gene expression. We further demonstrated that overexpression of full length, but not alternatively spliced variants of regucalcin, induces G1 and G2/M phase cell cycle arrest, suppressing the proliferation of MDA-MB-231 cells, a commonly used in vitro model of human breast cancer that metastasize to bone causing osteolytic lesions. Overexpression of regucalcin was found to suppress multiple signaling pathways including Akt, MAP kinase and SAPK/JNK, and NF-κB p65 and β-catenin along with increased p53, a tumor suppressor, and decreased K-ras, c-fos and c-jun. Moreover, we found that co-culture of regucalcin-overexpressing MDA-MB-231 cells with mouse bone marrow cells prevented enhanced osteoclastogenesis and suppressed mineralization in mouse bone marrow cells in vitro. Taken together, the present study suggests that regucalcin may have important anticancer properties in human breast cancer patients. Mechanistically, these effects are likely mediated through suppression of multiple signaling pathways, upregulation of p53 and downregulation of oncogenes leading to anti-proliferative effects and reduced metastases to bone, a phenotype associated with poor clinical outcome.

Prolonged survival in pancreatic cancer patients with increased regucalcin gene expression: Overexpression of regucalcin suppresses the proliferation in human pancreatic cancer MIA PaCa-2 cells in vitro

Approximately 90% of all pancreatic cancers are pancreatic ductal adenocarcinomas (PDAC). PDAC is a highly aggressive malignancy and is one of the deadliest. This poor clinical outcome is due to the prominent resistance of pancreatic cancer to drug and radiation therapies. Regucalcin plays a pivotal role as a suppressor protein in signal transduction in various types of cells including tumor tissues. We demonstrated that the prolonged survival is induced in PDAC patients with increased regucalcin gene expression using a dataset of PDAC obtained from GEO database (GSE17891) together with the clinical annotation data file. Moreover, overexpression of regucalcin with full length was demonstrated to suppress the proliferation, cell death and migration in human pancreatic cancer MIA PaCa-2 (K-ras mutated) cells that possess resistance to drug and radiation therapies. Suppressive effects of regucalcin on cell proliferation and death were not seen in the cells overexpressed with regucalcin cDNA alternatively spliced variants (deleted exon 4 or deleted exon 4 and 5). Regucalcin was suggested to induce G1 and G2/M phase cell cycle arrest in MIA PaCa-2 cells. Suppressive effects of regucalcin on cell proliferation were independent of cell death. Overexpression of regucalcin was found to suppress signaling pathways including Akt, MAP kinase and SAPK/JNK, to increase the protein levels of p53, a tumor suppresser, and to decrease K-ras, c-fos and c-jun, a oncogene, by suppressing signaling pathways that are related to signaling of K-ras. Regucalcin may play a potential role as a suppressor protein in human pancreatic cancer.

CALHM1 and its polymorphism P86L differentially control Ca²⁺homeostasis, mitogen-activated protein kinase signaling, and cell vulnerability upon exposure to amyloid β

The mutated form of the Ca²⁺ channel CALHM1 (Ca²⁺ homeostasis modulator 1), P86L‐CALHM1, has been correlated with early onset of Alzheimer's disease (AD). P86L‐CALHM1 increases production of amyloid beta (Aβ) upon extracellular Ca²⁺ removal and its subsequent addback. The aim of this study was to investigate the effect of the overexpression of CALHM1 and P86L‐CALHM, upon Aβ treatment, on the following: (i) the intracellular Ca²⁺ signal pathway; (ii) cell survival proteins ERK1/2 and Ca²⁺/cAMP response element binding (CREB); and (iii) cell vulnerability after treatment with Aβ. Using aequorins to measure the effect of nuclear Ca²⁺ concentrations ([Ca²⁺]_n) and cytosolic Ca²⁺ concentrations ([Ca²⁺]_c) on Ca²⁺ entry conditions, we observed that baseline [Ca²⁺]_n was higher in CALHM1 and P86L‐CALHM1 cells than in control cells. Moreover, exposure to Aβ affected [Ca²⁺]_c levels in HeLa cells overexpressing CALHM1 and P86L‐CALHM1 compared with control cells. Treatment with Aβ elicited a significant decrease in the cell survival proteins p‐ERK and p‐CREB, an increase in the activity of caspases 3 and 7, and more frequent cell death by inducing early apoptosis in P86L‐CALHM1‐overexpressing cells than in CALHM1 or control cells. These results suggest that in the presence of Aβ, P86L‐CALHM1 shifts the balance between neurodegeneration and neuronal survival toward the stimulation of pro‐cytotoxic pathways, thus potentially contributing to its deleterious effects in AD.

The flavonoid p-hydroxycinnamic acid exhibits anticancer effects in human pancreatic cancer MIA PaCa-2 cells in vitro: Comparison with gemcitabine

Pancreatic cancer is a highly aggressive malignancy with a notoriously dismal prognosis. A major contributor to this poor clinical outcome is pancreatic cancer's prominent chemoresistance. The present study was undertaken to determine whether the flavonoid p‑hydroxycinnamic acid (HCA), which is a botanical factor, possesses anticancer effects on cloned human pancreatic cancer MIA PaCa‑2 cells that possess resistance to radiation therapy in vitro. Proliferation of MIA PaCa‑2 cells was suppressed after culture with HCA (10‑1,000 nM). Such an effect was also noted in human pancreatic cancer Pt45P1 cells. In the MIA PaCa‑2 cells, HCA induced G1 and G2/M phase cell cycle arrest in the cells. The suppressive effects of HCA on proliferation were suggested to be mediated through the inhibition of various signaling pathways related to nuclear factor‑κB (NF‑κB), extracellular signal‑regulated kinase (ERK), protein kinase C, phosphatidylinositol 3‑kinase (PI3K) or nuclear transcription activity. Moreover, HCA was found to stimulate cell death in the MIA PaCa‑2 and Pt45P1 cells in vitro. The anticancer effects of HCA on MIA PaCa‑2 cells were exhibited at a lower concentration than gemcitabine, a potent cancer drug. The flavonoid HCA may be a useful tool in the therapy of human pancreatic cancer in vivo.

Lanthanum enhances glutamate-nitric oxide-3',5'-cyclic guanosine monophosphate pathway in the hippocampus of rats

Lanthanum (La) appears to impair learning and memory and increase the toxicity of excitatory amino acids in the central nervous system. The mechanism underlying excitotoxicity induced by La is still unclear. The purpose of this study was to investigate the hippocampal impairment of La exposure and possible mechanism involving the glutamate-nitric oxide (NO)-3'-5'-cyclic guanosine monophosphate (cGMP) pathway. In this study, lactating rats were exposed to 0, 0.25, 0.50, and 1.0% lanthanum chloride (LaCl3) in drinking water, respectively. Their offsprings were exposed to LaCl3 by parental lactation and then administrated with 0, 0.25, 0.50, and 1.0% LaCl3 in drinking water for 1 month. The results showed that La exposure impaired the neuronal ultrastructure and significantly increased the glutamate level, intracellular calcium ion concentrations, and NR1 and NR2B expression in the hippocampi. La exposure significantly enhanced messenger RNA expression and activity levels of inducible NO synthase and increased NO and cGMP levels in the hippocampi in a dose-dependent manner. These results indicate that the mechanism underlying excitotoxicity induced by La is possibly due to alterations of the glutamate-NO-cGMP signaling pathway in the hippocampus. The study provides new findings that may help prevent and improve treatments for La-induced neurotoxicity.

Preventing effect of L-type calcium channel blockade on electrophysiological alterations in dentate gyrus granule cells induced by entorhinal amyloid pathology

The entorhinal cortex (EC) is one of the earliest affected brain regions in Alzheimer's disease (AD). EC-amyloid pathology induces synaptic failure in the dentate gyrus (DG) with resultant behavioral impairment, but there is little known about its impact on neuronal properties in the DG. It is believed that calcium dyshomeostasis plays a pivotal role in the etiology of AD. Here, the effect of the EC amyloid pathogenesis on cellular properties of DG granule cells and also possible neuroprotective role of L-type calcium channel blockers (CCBs), nimodipine and isradipine, were investigated. The amyloid beta (Aβ) 1-42 was injected bilaterally into the EC of male rats and one week later, electrophysiological properties of DG granule cells were assessed. Voltage clamp recording revealed appearance of giant sIPSC in combination with a decrease in sEPSC frequency which was partially reversed by CCBs in granule cells from Aβ treated rats. EC amyloid pathogenesis induced a significant reduction of input resistance (Rin) accompanied by a profound decreased excitability in the DG granule cells. However, daily administration of CCBs, isradipine or nimodipine (i.c.v. for 6 days), almost preserved the normal excitability against Aβ. In conclusion, lower tendency to fire AP along with reduced Rin suggest that DG granule cells might undergo an alteration in the membrane ion channel activities which finally lead to the behavioral deficits observed in animal models and patients with early-stage Alzheimer's disease.

Simvastatin potently induces calcium-dependent apoptosis of human leiomyoma cells

Statins are drugs commonly used for the treatment of high plasma cholesterol levels. Beyond these well known lipid-lowering properties, they possess broad-reaching effects in vivo, including antitumor effects. Statins inhibit the growth of multiple tumors. However, the mechanisms remain incompletely understood. Here we show that simvastatin inhibits the proliferation of human leiomyoma cells. This was associated with decreased mitogen-activated protein kinase signaling and multiple changes in cell cycle progression. Simvastatin potently stimulated leiomyoma cell apoptosis in a manner mechanistically dependent upon apoptotic calcium release from voltage-gated calcium channels. Therefore, simvastatin possesses antitumor effects that are dependent upon the apoptotic calcium release machinery.

Ion channels in the regulation of apoptosis

Apoptosis, a type of genetically controlled cell death, is a fundamental cellular mechanism utilized by multicellular organisms for disposal of cells that are no longer needed or potentially detrimental. Given the crucial role of apoptosis in physiology, deregulation of apoptotic machinery is associated with various diseases as well as abnormalities in development. Acquired resistance to apoptosis represents the common feature of most and perhaps all types of cancer. Therefore, repairing and reactivating apoptosis represents a promising strategy to fight cancer. Accumulated evidence identifies ion channels as essential regulators of apoptosis. However, the contribution of specific ion channels to apoptosis varies greatly depending on cell type, ion channel type and intracellular localization, pathology as well as intracellular signaling pathways involved. Here we discuss the involvement of major types of ion channels in apoptosis regulation. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

3,4-Methylenedioxymethamphetamine enhances kainic acid convulsive susceptibility

Kainic acid (KA) causes seizures and neuronal loss in the hippocampus. The present study investigated whether a recreational schedule of 3,4-methylenedioxymethamphetamine (MDMA) favours the development of a seizure state in a model of KA-induced epilepsy and potentiates the toxicity profile of KA (20 or 30mg/kg). Adolescent male C57BL/6 mice received saline or MDMA t.i.d. (s.c. every 3h), on 1day a week, for 4 consecutive weeks. Twenty-four hours after the last MDMA exposure, the animals were injected with saline or KA (20 or 30mg/kg). After this injection, we evaluated seizures, hippocampal neuronal cell death, microgliosis, astrogliosis, and calcium binding proteins. MDMA pretreatment, by itself, did not induce neuronal damage but increased seizure susceptibility in all KA treatments and potentiated the presence of Fluoro-Jade-positive cells in CA1. Furthermore, MDMA, like KA, significantly decreased parvalbumin levels in CA1 and dentate gyrus, where it potentiated the effects of KA. The amphetamine derivative also promoted a transient decrease in calbindin and calretinin levels, indicative of an abnormal neuronal discharge. In addition, treatment of cortical neurons with MDMA (10-50μM) for 6 or 48h significantly increased basal Ca(2+), reduced basal Na(+) levels and potentiated kainate response. These results indicate that MDMA potentiates KA-induced neurodegeneration and also increases KA seizure susceptibility. The mechanism proposed includes changes in Calcium Binding Proteins expression, probably due to the disruption of intracellular ionic homeostasis, or/and an indirect effect through glutamate release.

ITH12410/SC058: a new neuroprotective compound with potential in the treatment of Alzheimer's disease

The neuroprotective profile of the dibenzothiadiazepine ITH12410/SC058 (2-chloro-5,6-dihydro-5,6-diacetyldibenzo[b,f][1,4,5]thiadiazepine) against several neurotoxicity models related to neurodegenerative diseases is herein described. ITH12410/SC058 protected SH-SY5Y cells against the loss of cell viability elicited by amyloid beta peptide and okadaic acid, a selective inhibitor of phosphoprotein phosphatase 2A that induces neurofibrillary tangle formation. Furthermore, ITH12410/SC058 is neuroprotective against several in vitro models of oxidative stress, that is, H2O2 exposure or incubation with rotenone plus oligomycin A in SH-SY5Y cells, and oxygen and glucose deprivation followed by reoxygenation in rat hippocampal slices. By contrast, ITH12410/SC058 was unable to significantly protect SH-SY5Y neuroblastoma cells against the toxicity elicited by Ca(2+) overload. Our results confirm the hypothesis that the dibenzothiadiazepine ITH12410/SC058 features its neuroprotective actions in a multitarget fashion, and is a promising drug for the treatment of neurodegenerative diseases.

Effects of intravenous human umbilical cord blood mesenchymal stem cell therapy versus gabapentin in pentylenetetrazole-induced chronic epilepsy in rats

AIM

The identification and application of stem cells to treat central nervous system disorders represent a dramatic evolution and expansion into the realms of neurorestoration and neuroregeneration. The aim of this study was to assess the possible ameliorative effect of mesenchymal stem cells (MSCs) in comparison to gabapentin on pentylenetetrazole (PTZ)-induced epileptogenesis and its consequences.

METHODS

Thirty-two rats were divided into 4 equal groups; group I: saline-injected group, group II: PTZ group, which received 13 intraperitoneal (i.p.) injections of PTZ (30 mg/kg) 3 times/week, groups III and IV: groups received PTZ and were treated with i.p. gabapentin (200 mg/kg) 60 min before each PTZ injection (group III) or a single intravenous injection of 10(6) MSCs/rat at day 22 (group IV).

RESULTS

Treatment with either gabapentin or MSCs demonstrated a significant improvement in the PTZ-induced epileptogenesis and its severe consequences, i.e. oxidative stress damage, motor and cognitive impairments. Moreover, they enhanced the GABA neurotransmitter levels. Meanwhile, MSC administration to chronic epileptic rats afforded more ameliorative effects on PTZ-induced epileptogenesis and its severe consequences in comparison to gabapentin.

CONCLUSION

These data indicate that MSCs were superior to gabapentin in ameliorating PTZ-induced epileptogenesis and verified the potential use of MSCs in seizure control, motor and cognitive impairments, oxidative stress, and the impairing GABA level in experimentally induced epilepsy.

Glutamate transporters in brain ischemia: to modulate or not?

In this review, we briefly describe glutamate (Glu) metabolism and its specific transports and receptors in the central nervous system (CNS). Thereafter, we focus on excitatory amino acid transporters, cystine/glutamate antiporters (system xc-) and vesicular glutamate transporters, specifically addressing their location and roles in CNS and the molecular mechanisms underlying the regulation of Glu transporters. We provide evidence from in vitro or in vivo studies concerning alterations in Glu transporter expression in response to hypoxia or ischemia, including limited human data that supports the role of Glu transporters in stroke patients. Moreover, the potential to induce brain tolerance to ischemia through modulation of the expression and/or activities of Glu transporters is also discussed. Finally we present strategies involving the application of ischemic preconditioning and pharmacological agents, eg β-lactam antibiotics, amitriptyline, riluzole and N-acetylcysteine, which result in the significant protection of nervous tissues against ischemia.

The anti-apoptotic effect of regucalcin is mediated through multisignaling pathways

Regucalcin (RGN/SMP30) was originally discovered in 1978 as a calcium-binding protein that does not contain the EF-hand motif of as a calcium-binding domain. The name, regucalcin, was proposed for this calcium-binding protein, which can regulate various Ca²⁺-dependent enzymes activation in liver cells. The regucalcin gene is localized on the X chromosome, and its expression is mediated through many signaling factors. Regucalcin plays a pivotal role in regulation of intracellular calcium homeostasis in various cell types. Regucalcin also has a suppressive effect on various signaling pathways from the cytoplasm to nucleus in proliferating cells and regulates nuclear function in including deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) synthesis. Overexpression of endogenous regucalcin was found to suppress apoptosis in modeled rat hepatoma cells and normal rat kidney proximal epithelial NRK52 cells induced by various signaling factors. Suppressive effect of regucalcin on apoptosis is related to inhibition of nuclear Ca²⁺-activated DNA fragmentation, Ca²⁺/calmodulin-dependent nitric oxide synthase, caspase-3, Bax, cytochrome C, protein tyrosine kinase, protein tyrosine phosphatase in the cytoplasm and nucleus. Moreover, regucalcin stimulates Bcl-2 mRNA expression and depresses enhancement of caspase-3, Apaf-1 and Akt-1 mRNAs expression. This review discusses that regucalcin plays a pivotal role in rescue of apoptotic cell death, which is mediated through various signaling factors.