A pharmacological screening approach for discovery of neuroprotective compounds in ischemic stroke

Discovery of a novel 2-spiroproline steroid mimetic scaffold for the potent inhibition of 11β-HSD1

11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) has been identified as the primary enzyme responsible for the activation of hepatic cortisone to cortisol in specific peripheral tissues, resulting in the concomitant antagonism of insulin action within these tissues. Dysregulation of 11β-HSD1, particularly in adipose tissues, has been associated with a variety of ailments including metabolic syndrome and type 2 diabetes mellitus. Therefore, inhibition of 11β-HSD1 with a small nonsteroidal molecule is therapeutically desirable. Implementation of a scaffold-hopping approach revealed a 3-point pharmacophore for 11β-HSD1 that was utilized to design a 2-spiroproline derivative as a steroid mimetic scaffold. Reiterative optimization provided valuable insight into the bioactive conformation of our novel scaffold and led to the discovery of several leads, such as compounds 39 and 51. Importantly, deleterious hERG inhibition and pregnane X receptor induction were mitigated by the introduction of a 4-hydroxyl group to the proline ring system.

An integrated chemo-informatics and in vitro experimental approach repurposes acarbose as a post-ischemic neuro-protectant

The increasing prevalence of ischemic stroke combined with limited therapeutic options highlights the compelling need for continued research into the development of future neuro-therapeutics. Death-Associated Protein Kinase 1 (DAPK1) and p53 protein-protein interaction serve as a signaling point for the convergence of apoptosis and necrosis in cerebral ischemia. In this study, we used an integrated chemo-informatics and in vitro experimental drug repurposing strategy to screen potential small-molecule inhibitors of DAPK1-p53 interaction from the United States of America Food and Drug Administration (FDA) approved drug database exhibiting post-ischemic neuroprotective and neuro-regenerative efficacy and mechanisms. The computational docking and molecular dynamics simulation of FDA-approved drugs followed by an in vitro experimental validation identified acarbose, an anti-diabetic medication and caloric restriction mimetic as a potential inhibitor of DAPK1-p53 interaction. The evaluation of post-ischemic neuroprotective and regenerative efficacy and mechanisms of action for acarbose was carried out using a set of experimental methods, including cell viability, proliferation and differentiation assays, fluorescence staining, and gene expression analysis. Post-ischemic administration of acarbose conferred significant neuroprotection against ischemia-reperfusion injury in vitro. The reduced fluorescence emission in cells stained with _pS²⁰ supported the potential of acarbose in inhibiting the DAPK1-p53 interaction. Acarbose prevented mitochondrial and lysosomal dysfunction, and favorably modulated gene expression related to cell survival, inflammation, and regeneration. BrdU staining and neurite outgrowth assay showed a significant increase in cell proliferation and differentiation in acarbose-treated group. This is the first study known to provide mechanistic insight into the post-ischemic neuroprotective and neuro-regenerative potential of acarbose. Our results provide a strong basis for preclinical studies to evaluate the safety and neuroprotective efficacy of acarbose against ischemic stroke.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-022-03130-5.

Optimisation of a PC12 cell-based in vitro stroke model for screening neuroprotective agents

Stroke causes death and disability globally but no neuroprotectant is approved for post-stroke neuronal injury. Neuroprotective compounds can be identified using oxygen glucose deprivation (OGD) of neuronal cells as an in vitro stroke model. Nerve growth factor (NGF)-differentiated PC12 pheochromocytoma cells are frequently used. However, investigators often find their clonal variant undifferentiable and are uncertain of optimal culture conditions. Hence we studied 3 commonly used PC12 variants: PC12 Adh, PC12 from Riken Cell Bank (PC12 Riken) and Neuroscreen-1 (NS-1) cells. We found DMEM the optimal media for PC12 Riken and NS-1 cells. Using a novel serum-free media approach, we identified collagen IV as the preferred adhesive substrate for both cell lines. We found PC12 Adh cells cannot attach without serum and is unable to differentiate using NGF. NS-1 cells differentiated to a maximal 72.7 ± 5.2% %, with substantial basal differentiation. We optimised differentiated NS-1 cells for an in vitro stroke model using 3 h of OGD resulting in ~ 70% viable cells. We screened 5 reported neuroprotectants and provide the first report that serotonin is antiapoptotic in a stroke model and the 5-HT_1A agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) is neuroprotective in PC12 cells. Thus we demonstrate the optimisation and validation for a PC12 cell-based in vitro stroke model.

Behavioral Changes in Combination Therapy of Ethanol and Modafinil on Rats Focal Cerebral Ischemia

Introduction:

Ethanol is considered as an effective agent in reducing brain stroke injury. In this study, we assessed the effects of modafinil along with ethanol as a combination therapy on behavioral function in Wistar rats.

Methods:

The right Middle Cerebral Artery Occlusion (MCAO) was performed and the rats were divided into nine groups (n=8 per group). The animal groups in this study were as follows: 1. MCAO control group (ischemia without treatment); 2. Vehicle group; 3. Modafinil group that was randomly subdivided into three groups receiving different doses of modafinil (10, 30, and 100 mg/kg) for 7 days before MCAO; 4. Ethanol group receiving 1.5 g/kg ethanol at the time of reperfusion; 5. Modafinil + ethanol group that was further subdivided into three groups receiving modafinil at different doses (10, 30, and 100 mg/kg) for 7 days before MCAO and ethanol at the time of reperfusion. The motor behavior was measured using the Garcia test 24, 48, and 72 h after the ischemia, and the elevated body swing test was performed 48 and 72 h after the ischemia. The anxiety and locomotor activity were analyzed by open field test 48 and 72 h post-ischemia.

Results:

The results showed that the neurological deficit score, locomotor activity, and unexpected thigmotaxis (anxiety) in the ethanol, modafinil (in a dose-dependent manner), and ethanol+modafinil treatment groups were significantly higher than the MCAO control group.

Conclusion:

It seems that the combination therapy of modafinil (100 mg/kg) and ethanol (1.5 g/kg) significantly enhanced neuroprotection via an improvement in locomotor activity and neurological functions.

Neuroprotective effect of ethanol and Modafinil on focal cerebral ischemia in rats

Ethanol is known as an effective agent against cerebral lesions after ischemia. Modafinil is a stimulant of the central nervous system (CNS) with antioxidant properties. We assessed the neuroprotective effect of modafinil in combination with ethanol after focal cerebral ischemia. Male wistar rats weighing 280-300 g were divided into nine groups (n = 12 each group): The groups consisted of the MCAO (middle cerebral artery occlusion) group (i.e. ischemia without treatment); the vehicle group(Dimethylsulfoxide); the modafinil group including three subgroups which pretreated with Modafinil (10, 30, 100 mg/kg), respectively, for seven days prior to the induction of MCAO; the ethanol group which received 1.5g/kg ethanol at the time of reperfusion; and modafinil+ethanol group which was divided into three subgroups that received three doses of modanifil (10, 30,100 mg/kg), respectively, for seven days prior to MCAO as well as ethanol at the time of reperfusion. Transient cerebral ischemia was induced by 60-min intraluminal occlusion of the right middle cerebral artery. Edema, infarct volume, glial scar formation (gliosis) and apoptosis were analyzed. The ethanol alone treatment (with a less significant effect), modafinil (in a dose-dependent way), and the combination of modafinil and ethanol significantly decreased the brain infarct volume, edema, apoptosis, and gliosis (P ≤ 0.05). Additionally, modafinil+ethanol mediated the restoration of aerobic metabolism and hyper-glycolysis suppress, thereby resulting in an increase in pyruvate dehydrogenase and a decrease in lactate dehydrogenase activity, respectively, which ultimately reduced oxidative reperfusion injury. These results demonstrate that pretreatment with modafinil (100 mg/kg) and modafinil+ethanol(1.5 g/kg) may prevent ischemic brain injuries.

11β-hydroxysteroid dehydrogenase-1 deficiency alters brain energy metabolism in acute systemic inflammation

Chronically elevated glucocorticoid levels impair cognition and are pro-inflammatory in the brain. Deficiency or inhibition of 11β-hydroxysteroid dehydrogenase type-1 (11β-HSD1), which converts inactive into active glucocorticoids, protects against glucocorticoid-associated chronic stress- or age-related cognitive impairment. Here, we hypothesised that 11β-HSD1 deficiency attenuates the brain cytokine response to inflammation. Because inflammation is associated with altered energy metabolism, we also examined the effects of 11β-HSD1 deficiency upon hippocampal energy metabolism. Inflammation was induced in 11β-HSD1 deficient (Hsd11b1Del/Del) and C57BL/6 control mice by intraperitoneal injection of lipopolysaccharide (LPS). LPS reduced circulating neutrophil and monocyte numbers and increased plasma corticosterone levels equally in C57BL/6 and Hsd11b1Del/Del mice, suggesting a similar peripheral inflammatory response. However, the induction of pro-inflammatory cytokine mRNAs in the hippocampus was attenuated in Hsd11b1Del/Del mice. Principal component analysis of mRNA expression revealed a distinct metabolic response to LPS in hippocampus of Hsd11b1Del/Del mice. Expression of Pfkfb3 and Ldha, key contributors to the Warburg effect, showed greater induction in Hsd11b1Del/Del mice. Consistent with increased glycolytic flux, levels of 3-phosphoglyceraldehyde and dihydroxyacetone phosphate were reduced in hippocampus of LPS injected Hsd11b1Del/Del mice. Expression of Sdha and Sdhb, encoding subunits of succinate dehydrogenase/complex II that determines mitochondrial reserve respiratory capacity, was induced specifically in hippocampus of LPS injected Hsd11b1Del/Del mice, together with increased levels of its product, fumarate. These data suggest 11β-HSD1 deficiency attenuates the hippocampal pro-inflammatory response to LPS, associated with increased capacity for aerobic glycolysis and mitochondrial ATP generation. This may provide better metabolic support and be neuroprotective during systemic inflammation or aging.

iDrugs and iDevices Discovery Research: Preclinical Assays, Techniques, and Animal Model Studies for Ocular Hypotensives and Neuroprotectants

Discovery ophthalmic research is centered around delineating the molecular and cellular basis of ocular diseases and finding and exploiting molecular and genetic pathways associated with them. From such studies it is possible to determine suitable intervention points to address the disease process and hopefully to discover therapeutics to treat them. An investigational new drug (IND) filing for a new small-molecule drug, peptide, antibody, genetic treatment, or a device with global health authorities requires a number of preclinical studies to provide necessary safety and efficacy data. Specific regulatory elements needed for such IND-enabling studies are beyond the scope of this article. However, to enhance the overall data packages for such entities and permit high-quality foundation-building publications for medical affairs, additional research and development studies are always desirable. This review aims to provide examples of some target localization/verification, ocular drug discovery processes, and mechanistic and portfolio-enhancing exploratory investigations for candidate drugs and devices for the treatment of ocular hypertension and glaucomatous optic neuropathy (neurodegeneration of retinal ganglion cells and their axons). Examples of compound screening assays, use of various technologies and techniques, deployment of animal models, and data obtained from such studies are also presented.

Neural patterning of human induced pluripotent stem cells in 3-D cultures for studying biomolecule-directed differential cellular responses

INTRODUCTION

Appropriate neural patterning of human induced pluripotent stem cells (hiPSCs) is critical to generate specific neural cells/tissues and even mini-brains that are physiologically relevant to model neurological diseases. However, the capacity of signaling factors that regulate 3-D neural tissue patterning in vitro and differential responses of the resulting neural populations to various biomolecules have not yet been fully understood.

METHODS

By tuning neural patterning of hiPSCs with small molecules targeting sonic hedgehog (SHH) signaling, this study generated different 3-D neuronal cultures that were mainly comprised of either cortical glutamatergic neurons or motor neurons.

RESULTS

Abundant glutamatergic neurons were observed following the treatment with an antagonist of SHH signaling, cyclopamine, while Islet-1 and HB9-expressing motor neurons were enriched by an SHH agonist, purmorphamine. In neurons derived with different neural patterning factors, whole-cell patch clamp recordings showed similar voltage-gated Na(+)/K(+) currents, depolarization-evoked action potentials and spontaneous excitatory post-synaptic currents. Moreover, these different neuronal populations exhibited differential responses to three classes of biomolecules, including (1) matrix metalloproteinase inhibitors that affect extracellular matrix remodeling; (2) N-methyl-d-aspartate that induces general neurotoxicity; and (3) amyloid β (1-42) oligomers that cause neuronal subtype-specific neurotoxicity.

CONCLUSIONS

This study should advance our understanding of hiPSC self-organization and neural tissue development and provide a transformative approach to establish 3-D models for neurological disease modeling and drug discovery.

STATEMENT OF SIGNIFICANCE

Appropriate neural patterning of human induced pluripotent stem cells (hiPSCs) is critical to generate specific neural cells, tissues and even mini-brains that are physiologically relevant to model neurological diseases. However, the capability of sonic hedgehog-related small molecules to tune different neuronal subtypes in 3-D differentiation from hiPSCs and the differential cellular responses of region-specific neuronal subtypes to various biomolecules have not been fully investigated. By tuning neural patterning of hiPSCs with small molecules targeting sonic hedgehog signaling, this study provides knowledge on the differential susceptibility of region-specific neuronal subtypes derived from hiPSCs to different biomolecules in extracellular matrix remodeling and neurotoxicity. The findings are significant for understanding 3-D neural patterning of hiPSCs for the applications in brain organoid formation, neurological disease modeling, and drug discovery.

High-throughput platforms for the screening of new therapeutic targets for neurodegenerative diseases

Despite the recent progress in the understanding of neurodegenerative disorders, a lack of solid fundamental knowledge on the etiology of many of the major neurodegenerative diseases has made it difficult to obtain effective therapies to treat these conditions. Scientists have been looking to carry out more-human-relevant studies, with strong statistical power, to overcome the limitations of preclinical animal models that have contributed to the failure of numerous therapeutics in clinical trials. Here, we identify currently existing platforms to mimic central nervous system tissues, healthy and diseased, mainly focusing on cell-based platforms and discussing their strengths and limitations in the context of the high-throughput screening of new therapeutic targets and drugs.

11β-hydroxysteroid dehydrogenase inhibition as a new potential therapeutic target for alcohol abuse

The identification of new and more effective treatments for alcohol abuse remains a priority. Alcohol intake activates glucocorticoids, which have a key role in alcohol's reinforcing properties. Glucocorticoid effects are modulated in part by the activity of 11β-hydroxysteroid dehydrogenases (11β-HSD) acting as pre-receptors. Here, we tested the effects on alcohol intake of the 11β-HSD inhibitor carbenoxolone (CBX, 18β-glycyrrhetinic acid 3β-O-hemisuccinate), which has been extensively used in the clinic for the treatment of gastritis and peptic ulcer and is active on both 11β-HSD1 and 11β-HSD2 isoforms. We observed that CBX reduces both baseline and excessive drinking in rats and mice. The CBX diastereomer 18α-glycyrrhetinic acid 3β-O-hemisuccinate (αCBX), which we found to be selective for 11β-HSD2, was also effective in reducing alcohol drinking in mice. Thus, 11β-HSD inhibitors may be a promising new class of candidate alcohol abuse medications, and existing 11β-HSD inhibitor drugs may be potentially re-purposed for alcohol abuse treatment.

Endothelin uncouples gap junctions in sustentacular cells and olfactory ensheathing cells of the olfactory mucosa

Several factors modulate the first step of odour detection in the rat olfactory mucosa (OM). Among others, vasoactive peptides such as endothelin might play multifaceted roles in the different OM cells. Like their counterparts in the central nervous system, the olfactory sensory neurons are encompassed by different glial-like non-neuronal OM cells; sustentacular cells (SCs) surround their cell bodies, whereas olfactory ensheathing cells (OECs) wrap their axons. Whereas SCs maintain both the structural and ionic integrity of the OM, OECs assure protection, local blood flow control and guiding of olfactory sensory neuron axons toward the olfactory bulb. We previously showed that these non-neuronal OM cells are particularly responsive to endothelin in vitro. Here, we confirmed that the endothelin system is strongly expressed in the OM using in situ hybridization. We then further explored the effects of endothelin on SCs and OECs using electrophysiological recordings and calcium imaging approaches on both in vitro and ex vivo OM preparations. Endothelin induced both robust calcium signals and gap junction uncoupling in both types of cells. This latter effect was mimicked by carbenoxolone, a known gap junction uncoupling agent. However, although endothelin is known for its antiapoptotic effect in the OM, the uncoupling of gap junctions by carbenoxolone was not sufficient to limit the cellular death induced by serum deprivation in OM primary culture. The functional consequence of the endothelin 1-induced reduction of the gap junctional communication between OM non-neuronal cells thus remains to be elucidated.

Identification of isoxsuprine hydrochloride as a neuroprotectant in ischemic stroke through cell-based high-throughput screening

Stroke is a leading cause of death and disability and treatment options are limited. A promising approach to accelerate the development of new therapeutics is the use of high-throughput screening of chemical libraries. Using a cell-based high-throughput oxygen-glucose deprivation (OGD) model, we evaluated 1,200 small molecules for repurposed application in stroke therapy. Isoxsuprine hydrochloride was identified as a potent neuroprotective compound in primary neurons exposed to OGD. Isoxsuprine, a β₂-adrenergic agonist and NR2B subtype-selective N-methyl-D-aspartate (NMDA) receptor antagonist, demonstrated no loss of efficacy when administered up to an hour after reoxygenation in an in vitro stroke model. In an animal model of transient focal ischemia, isoxsuprine significantly reduced infarct volume compared to vehicle (137±18 mm³ versus 279±25 mm³, p<0.001). Isoxsuprine, a peripheral vasodilator, was FDA approved for the treatment of cerebrovascular insufficiency and peripheral vascular disease. Our demonstration of the significant and novel neuroprotective action of isoxsuprine hydrochloride in an in vivo stroke model and its history of human use suggest that isoxsuprine may be an ideal candidate for further investigation as a potential stroke therapeutic.