Transcriptional regulation of ncx1 gene in the brain

Hypoxia-inducible factor-1: Regulatory mechanisms and drug development in stroke

Stroke is an acute cerebrovascular disease caused by sudden rupture of blood vessels in the brain or blockage of blood vessels, which has now become one of the main causes of adult death. During stroke, hypoxia-inducible factor-1 (HIF-1), as an important regulator under hypoxia conditions, is involved in the pathological process of stroke by regulating multi-pathways, such as glucose metabolism, angiogenesis, erythropoiesis, cell survival. However, the roles of HIF-1 in stroke are still controversial, which are related with ischemic time and degree of ischemia. The regulatory mechanisms of HIF-1 in stroke include inflammation, autophagy, oxidative stress, apoptosis and energy metabolism. The potential drugs targeting HIF-1 have attracted more attention, such as HIF-1 inhibitors, HIF-1 stabilizers and natural products. Based on the role of HIF-1 in stroke, HIF-1 is expected to be a potential target for stroke treatment. Resolving when and what interventions for HIF-1 to take during stroke will provide novel strategies for stroke treatment.

The transcription factor Nurr1 is upregulated in amyotrophic lateral sclerosis patients and SOD1-G93A mice

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that affects both lower and upper motor neurons (MNs) in the central nervous system. ALS etiology is highly multifactorial and multifarious, and an effective treatment is still lacking. Neuroinflammation is a hallmark of ALS and could be targeted to develop new therapeutic approaches. Interestingly, the transcription factor Nurr1 has been demonstrated to have an important role in the inflammatory process in several neurological disorders, such as Parkinson's disease and multiple sclerosis. In the present paper, we demonstrate for the first time that Nurr1 expression levels are upregulated in the peripheral blood of ALS patients. Moreover, we investigated Nurr1 function in the SOD1-G93A mouse model of ALS. Nurr1 was strongly upregulated in the spinal cord during the asymptomatic and early symptomatic phases of the disease, where it promoted the expression of brain-derived neurotrophic factor mRNA and the repression of NFκB pro-inflammatory targets, such as inducible nitric oxide synthase. Therefore, we hypothesize that Nurr1 is activated in an early phase of the disease as a protective endogenous anti-inflammatory mechanism, although not sufficient to reverse disease progression. On the basis of these observations, Nurr1 could represent a potential biomarker for ALS and a promising target for future therapies.

miR-206 Reduces the Severity of Motor Neuron Degeneration in the Facial Nuclei of the Brainstem in a Mouse Model of SMA

Spinal muscular atrophy (SMA) is a severe neuromuscular disease affecting infants caused by alterations of the survival motor neuron gene, which results in progressive degeneration of motor neurons (MNs). Although an effective treatment for SMA patients has been recently developed, the molecular pathway involved in selective MN degeneration has not been yet elucidated. In particular, miR-206 has been demonstrated to play a relevant role in the regeneration of neuromuscular junction in several MN diseases, and particularly it is upregulated in the quadriceps, tibialis anterior, spinal cord, and serum of SMA mice. In the present paper, we demonstrated that miR-206 was transiently upregulated also in the brainstem of the mouse model of SMA, SMAΔ7, in the early phase of the disease paralleling MN degeneration and was down-regulated in the late symptomatic phase. To prevent this downregulation, we intracerebroventricularly injected miR-206 in SMA pups, demonstrating that miR-206 reduced the severity of SMA pathology, slowing down disease progression, increasing survival rate, and improving behavioral performance of mice. Interestingly, exogenous miRNA-206-induced upregulation caused a reduction of the predicted target sodium calcium exchanger isoform 2, NCX2, one of the main regulators of intracellular [Ca²⁺] and [Na⁺]. Therefore, we hypothesized that miR-206 might exert part of its neuroprotective effect modulating NCX2 expression in SMA disease.

Anti-miR-223-5p Ameliorates Ischemic Damage and Improves Neurological Function by Preventing NCKX2 Downregulation after Ischemia in Rats

It has been demonstrated that the K⁺-dependent Na⁺/Ca²⁺ exchanger, NCKX2, is a new promising stroke neuroprotective target. However, because no pharmacological activator of NCKX2 is still available, microRNA (miRNA) may represent an alternative method to modulate NCKX2 expression. In particular, by bioinformatics analysis, miR-223-5p emerged as a possible modulator of NCKX2 expression. In the light of these premises, the aims of the present study were: (1) to evaluate miR-223-5p and NCKX2 expression in the temporoparietal cortex and striatum of rats subjected to transient middle cerebral artery occlusion; (2) to evaluate whether miR-223-5p targets the 3′ UTR of the NCKX2 transcript; and (3) to evaluate the effect of miR-223-5p modulation on brain ischemic volume and neurological deficits. Our results showed that miR-223-5p expression increased in a time-dependent manner in the striatum of ischemic rats in parallel with NCKX2 downregulation, and that the transfection of cortical neurons with miR-223-5p induced a reduction of NCKX2 expression. Moreover, a luciferase assay showed that miR-223-5p specifically interacts with the NCKX2 3′ UTR subregion (+7037 to +8697), thus repressing NCKX2 translation. More interestingly, intracerebroventricular infusion of anti-miR-223-5p prevented NCKX2 downregulation after ischemia, thus promoting neuroprotection. The present findings support the idea that blocking miR-223-5p by antimiRNA is a reasonable strategy to reduce the neurodetrimental effect induced by NCKX2 downregulation during brain ischemia.

Type 1 Sodium Calcium Exchanger Forms a Complex with Carbonic Anhydrase IX and Via Reverse Mode Activity Contributes to pH Control in Hypoxic Tumors

Hypoxia and acidosis are among the key microenvironmental factors that contribute to cancer progression. We have explored a possibility that the type 1Na⁺/Ca²⁺ exchanger (NCX1) is involved in pH control in hypoxic tumors. We focused on changes in intracellular pH, co-localization of NCX1, carbonic anhydrase IX (CA IX), and sodium proton exchanger type 1 (NHE1) by proximity ligation assay, immunoprecipitation, spheroid formation assay and migration of cells due to treatment with KB-R7943, a selective inhibitor of the reverse-mode NCX1. In cancer cells exposed to hypoxia, reverse-mode NCX1 forms a membrane complex primarily with CA IX and also with NHE1. NCX1/CA IX/NHE1 assembly operates as a metabolon with a potent ability to extrude protons to the extracellular space and thereby facilitate acidosis. KB-R7943 prevents formation of this metabolon and reduces cell migration. Thus, we have shown that in hypoxic cancer cells, NCX1 operates in a reverse mode and participates in pH regulation in hypoxic tumors via cooperation with CAIX and NHE1.

A Novel Model for Studying Voltage-Gated Ion Channel Gene Expression during Reversible Ischemic Stroke

The dysfunction of voltage-gated ion channels contributes to the pathology of ischemic stroke. In this study, we developed rat models of transient ischemic attack (TIA) and reversible ischemic neurological deficit (RIND) that was induced via the injection of artificial embolic particles during full consciousness, that allow us to monitor the neurologic deficit and positron emission tomography (PET) scans in real-time. We then evaluated the infarction volume of brain tissue was confirmed by 2,3,5-triphenyl tetrazolium chloride (TTC) staining, and gene expressions were evaluated by quantitative real-time PCR (qPCR). We found that rats with TIA or RIND exhibited neurological deficits as determined by negative TTC and PET findings. However, the expression of voltage-gated sodium channels in the hippocampus was significantly up-regulated in the qPCR array study. Furthermore, an altered expression of sodium channel β-subunits and potassium channels, were observed in RIND compared to TIA groups. In conclusion, to our knowledge, this is the first report of the successful evaluation of voltage-gated ion channel gene expression in TIA and RIND animal models. This model will aid future studies in investigating pathophysiological mechanisms, and in developing new therapeutic compounds for the treatment of TIA and RIND.

Mn Porphyrin-Based Redox-Active Drugs: Differential Effects as Cancer Therapeutics and Protectors of Normal Tissue Against Oxidative Injury

SIGNIFICANCE

After approximatelty three decades of research, two Mn(III) porphyrins (MnPs), MnTE-2-PyP⁵⁺ (BMX-010, AEOL10113) and MnTnBuOE-2-PyP⁵⁺ (BMX-001), have progressed to five clinical trials. In parallel, another similarly potent metal-based superoxide dismutase (SOD) mimic-Mn(II)pentaaza macrocycle, GC4419-has been tested in clinical trial on application, identical to that of MnTnBuOE-2-PyP⁵⁺-radioprotection of normal tissue in head and neck cancer patients. This clearly indicates that Mn complexes that target cellular redox environment have reached sufficient maturity for clinical applications. Recent Advances: While originally developed as SOD mimics, MnPs undergo intricate interactions with numerous redox-sensitive pathways, such as those involving nuclear factor κB (NF-κB) and nuclear factor E2-related factor 2 (Nrf2), thereby impacting cellular transcriptional activity. An increasing amount of data support the notion that MnP/H₂O₂/glutathione (GSH)-driven catalysis of S-glutathionylation of protein cysteine, associated with modification of protein function, is a major action of MnPs on molecular level.

CRITICAL ISSUES

Differential effects of MnPs on normal versus tumor cells/tissues, which support their translation into clinic, arise from differences in their accumulation and redox environment of such tissues. This in turn results in different yields of MnP-driven modifications of proteins. Thus far, direct evidence for such modification of NF-κB, mitogen-activated protein kinases (MAPK), phosphatases, Nrf2, and endogenous antioxidative defenses was provided in tumor, while indirect evidence shows the modification of NF-κB and Nrf2 translational activities by MnPs in normal tissue.

FUTURE DIRECTIONS

Studies that simultaneously explore differential effects in same animal are lacking, while they are essential for understanding of extremely intricate interactions of metal-based drugs with complex cellular networks of normal and cancer cells/tissues.

Astaxanthin protects astrocytes against trauma-induced apoptosis through inhibition of NKCC1 expression via the NF-κB signaling pathway

BACKGROUND

Astaxanthin (ATX) is a carotenoid pigment with pleiotropic pharmacological properties that is seen as a possible drug for treating cerebral ischemic injury and subarachnoid hemorrhage. Na⁺-K⁺-2Cl^- co-transporter-1 (NKCC1), an intrinsic membrane protein expressed by many cell types, is activated by various insults, leading to the formation of cell swelling and brain edema. We previously established that ATX attenuated brain edema and improved neurological outcomes by modulating NKCC1 expression after traumatic brain injury in mice. This paper explored the molecular mechanism of ATX-mediated inhibition of NKCC1 utilizing an in vitro astrocyte stretch injury model.

RESULTS

Stretch injury in cultured astrocytes lowered cell viability time-dependently, which was substantially reducing by pretreating with ATX (50 μmol/L). Stretch injury increased Bax level and cleaved caspase-3 activity, and decreased Bcl-2 level and pro-caspase 3 activity, resulting in the apoptosis of astrocytes. Additionally, stretch injury substantially raised the gene and protein expressions of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α and prompted the expression and nuclear translocation of NF-κB. Pretreatment with ATX remarkably prevented the trauma-induced initiation of NF-κB, expressions of pro-inflammatory cytokines, and cell apoptosis. Moreover, stretch injury markedly elevated the gene and protein expression of NKCC1, which was partly blocked by co-treatment with ATX (50 µmol/L) or an NF-κB inhibitor (PDTC, 10 µmol/L). Cleaved caspase-3 activity was partially reduced by PDTC (10 µmol/L) or an NKCC1 inhibitor (bumetanide, 50 µmol/L).

CONCLUSIONS

ATX attenuates apoptosis after stretch injury in cultured astrocytes by inhibiting NKCC1 expression, and it acts by reducing the expression of NF-κB-mediated pro-inflammatory factors.

KB-R7943 reduces 4-aminopyridine-induced epileptiform activity in adult rats after neuronal damage induced by neonatal monosodium glutamate treatment

BACKGROUND

Neonatal monosodium glutamate (MSG) treatment triggers excitotoxicity and induces a degenerative process that affects several brain regions in a way that could lead to epileptogenesis. Na+/Ca2+ exchangers (NCX1-3) are implicated in Ca2+ brain homeostasis; normally, they extrude Ca2+ to control cell inflammation, but after damage and in epilepsy, they introduce Ca2+ by acting in the reverse mode, amplifying the damage. Changes in NCX3 expression in the hippocampus have been reported immediately after neonatal MSG treatment. In this study, the expression level of NCX1-3 in the entorhinal cortex (EC) and hippocampus (Hp); and the effects of blockade of NCXs on the seizures induced by 4-Aminopyridine (4-AP) were analysed in adult rats after neonatal MSG treatment. KB-R7943 was applied as NCXs blocker, but is more selective to NCX3 in reverse mode.

METHODS

Neonatal MSG treatment was applied to newborn male rats at postnatal days (PD) 1, 3, 5, and 7 (4 g/kg of body weight, s.c.). Western blot analysis was performed on total protein extracts from the EC and Hp to estimate the expression level of NCX1-3 proteins in relative way to the expression of β-actin, as constitutive protein. Electrographic activity of the EC and Hp were acquired before and after intracerebroventricular (i.c.v.) infusion of 4-AP (3 nmol) and KB-R7943 (62.5 pmol), alone or in combination. All experiments were performed at PD60. Behavioural alterations were also recorder.

RESULTS

Neonatal MSG treatment significantly increased the expression of NCX3 protein in both studied regions, and NCX1 protein only in the EC. The 4-AP-induced epileptiform activity was significantly higher in MSG-treated rats than in controls, and KB-R7943 co-administered with 4-AP reduced the epileptiform activity in more prominent way in MSG-treated rats than in controls.

CONCLUSIONS

The long-term effects of neonatal MSG treatment include increases on functional expression of NCXs (mainly of NCX3) in the EC and Hp, which seems to contribute to improve the control that KB-R7943 exerted on the seizures induced by 4-AP in adulthood. The results obtained here suggest that the blockade of NCXs could improve seizure control after an excitotoxic process; however, this must be better studied.

Activation of NF-κB mediates astrocyte swelling and brain edema in traumatic brain injury

Brain edema and associated increased intracranial pressure are major consequences of traumatic brain injury (TBI). While astrocyte swelling (cytotoxic edema) represents a major component of the brain edema in the early phase of TBI, its mechanisms are unclear. One factor known to be activated by trauma is nuclear factor-κB (NF-κB). Because this factor has been implicated in the mechanism of cell swelling/brain edema in other neurological conditions, we examined whether NF-κB might also be involved in the mediation of post-traumatic astrocyte swelling/brain edema. Here we show an increase in NF-κB activation in cultured astrocytes at 1 and 3 h after trauma (fluid percussion injury, FPI), and that BAY 11-7082, an inhibitor of NF-κB, significantly blocked the trauma-induced astrocyte swelling. Increased activities of nicotinamide adenine dinucleotide phosphate-oxidase and the Na(+), K(+), 2Cl(-) cotransporter were also observed in cultured astrocytes after trauma, and BAY 11-7082 reduced these effects. We also examined the role of NF-κB in the mechanism of cell swelling by using astrocyte cultures derived from transgenic (Tg) mice with a functional inactivation of astrocytic NF-κB. Exposure of cultured astrocytes from wild-type mice to in vitro trauma (3 h) caused a significant increase in cell swelling. By contrast, traumatized astrocyte cultures derived from NF-κB Tg mice showed no swelling. We also found increased astrocytic NF-κB activation and brain water content in rats after FPI, while BAY 11-7082 significantly reduced such effects. Our findings strongly suggest that activation of astrocytic NF-κB represents a key element in the process by which cytotoxic brain edema occurs after TBI.

SOD therapeutics: latest insights into their structure-activity relationships and impact on the cellular redox-based signaling pathways

SIGNIFICANCE

Superoxide dismutase (SOD) enzymes are indispensable and ubiquitous antioxidant defenses maintaining the steady-state levels of O2·(-); no wonder, thus, that their mimics are remarkably efficacious in essentially any animal model of oxidative stress injuries thus far explored.

RECENT ADVANCES

Structure-activity relationship (half-wave reduction potential [E1/2] versus log kcat), originally reported for Mn porphyrins (MnPs), is valid for any other class of SOD mimics, as it is dominated by the superoxide reduction and oxidation potential. The biocompatible E1/2 of ∼+300 mV versus normal hydrogen electrode (NHE) allows powerful SOD mimics as mild oxidants and antioxidants (alike O2·(-)) to readily traffic electrons among reactive species and signaling proteins, serving as fine mediators of redox-based signaling pathways. Based on similar thermodynamics, both SOD enzymes and their mimics undergo similar reactions, however, due to vastly different sterics, with different rate constants.

CRITICAL ISSUES

Although log kcat(O2·(-)) is a good measure of therapeutic potential of SOD mimics, discussions of their in vivo mechanisms of actions remain mostly of speculative character. Most recently, the therapeutic and mechanistic relevance of oxidation of ascorbate and glutathionylation and oxidation of protein thiols by MnP-based SOD mimics and subsequent inactivation of nuclear factor κB has been substantiated in rescuing normal and killing cancer cells. Interaction of MnPs with thiols seems to be, at least in part, involved in up-regulation of endogenous antioxidative defenses, leading to the healing of diseased cells.

FUTURE DIRECTIONS

Mechanistic explorations of single and combined therapeutic strategies, along with studies of bioavailability and translational aspects, will comprise future work in optimizing redox-active drugs.

Does Na⁺/Ca²⁺ exchanger, NCX, represent a new druggable target in stroke intervention?

Stroke causes a rapid cell death in the core of the injured region and triggers mechanisms in surrounding penumbra area that leads to changes in concentrations of several ions like intracellular Ca²⁺, Na⁺, H⁺, K⁺, and radicals such as reactive oxygen species and reactive nitrogen species. When a dysregulation of homeostasis of these messengers occurs, it can trigger cell death. In particular, it is widely accepted that a critical factor in determining neuronal death during cerebral ischemia is progressive dysregulation of Ca²⁺, Na⁺, K⁺, and H⁺ homeostasis that activate several death pathways, including oxidative and nitrosative stress, mitochondrial dysfunction, protease activation, and apoptosis. In the last decade, several seminal experimental works are markedly changing the scenario of research of principal players of an ischemic event. Indeed, some plasma membrane channels and transporters, involved in the control of Ca²⁺, Na⁺, K⁺, and H⁺ ion influx or efflux and, therefore, responsible for maintaining the homeostasis of these four cations, might function as crucial players in initiation of brain ischemic process. Indeed, these proteins, by regulating ionic homeostasis, may provide the molecular basis underlying glutamate-independent Ca²⁺ and Na⁺ overload mechanisms in neuronal ischemic cell death and, most importantly, may represent more suitable molecular targets for therapeutic intervention. Recently, a great deal of interest has been devoted to clarify the role of the plasma membrane protein known as Na⁺/Ca²⁺ exchanger, a transporter able to control Na⁺ and Ca²⁺ homeostasis. In this review, the pathophysiological role of NCX and its implication as a potential target in stroke intervention will be examined.

Sodium/calcium exchanger is upregulated by sulfide signaling, forms complex with the β1 and β3 but not β2 adrenergic receptors, and induces apoptosis

Hydrogen sulfide (H2S) as a novel gasotransmitter regulates variety of processes, including calcium transport systems. Sodium calcium exchanger (NCX) is one of the key players in a regulation calcium homeostasis. Thus, the aims of our work were to determine effect of sulfide signaling on the NCX type 1 (NCX1) expression and function in HeLa cells, to investigate the relationship of β-adrenergic receptors with the NCX1 in the presence and/or absence of H2S, and to determine physiological importance of this potential communication. As a H2S donor, we used morpholin-4-ium-4-methoxyphenyl(morpholino) phosphinodithioate-GYY4137. We observed increased levels of the NCX1 mRNA, protein, and activity after 24 h of GYY4137 treatment. This increase was accompanied by elevated cAMP due to the GYY4137 treatment, which was completely abolished, when NCX1 was silenced. Increased cAMP levels would point to upregulation of β-adrenergic receptors. Indeed, GYY4137 increased expression of β1 and β3 (but not β2) adrenergic receptors. These receptors co-precipitated, co-localized with the NCX1, and induced apoptosis in the presence of H2S. Our results suggest that sulfide signaling plays a role in regulation of the NCX1, β1 and β3 adrenergic receptors, their co-localization, and stimulation of apoptosis, which might be of a potential importance in cancer treatment.

Insight into the family of Na+/Ca2+ exchangers of Caenorhabditis elegans

Here we provide the first genome-wide in vivo analysis of the Na+/Ca2+ exchanger family in the model system Caenorhabditis elegans. We source all members of this family within the Caenorhabditis genus and reconstruct their phylogeny across humans and Drosophila melanogaster. Next, we provide a description of the expression pattern for each exchanger gene in C. elegans, revealing a wide expression in a number of tissues and cell types including sensory neurons, interneurons, motor neurons, muscle cells, and intestinal tissue. Finally, we conduct a series of behavioral and functional analyses through mutant characterization in C. elegans. From these data we demonstrate that, similar to mammalian systems, the expression of Na+/Ca2+ exchangers in C. elegans is skewed toward excitable cells, and we propose that C. elegans may be an ideal model system for the study of Na+/Ca2+ exchangers.