Emerging targets in drug discovery against neurodegenerative diseases: Control of synapsis disfunction by the RhoA/ROCK pathway

Mertk Reduces Blood-Spinal Cord Barrier Permeability Through the Rhoa/Rock1/P-MLC Pathway After Spinal Cord Injury

Disruption of the blood-spinal cord barrier (BSCB) is a critical event in the secondary injury following spinal cord injury (SCI). Mertk has been reported to play an important role in regulating inflammation and cytoskeletal dynamics. However, the specific involvement of Mertk in BSCB remains elusive. Here, we demonstrated a distinct role of Mertk in the repair of BSCB. Mertk expression is decreased in endothelial cells following SCI. Overexpression of Mertk upregulated tight junction proteins (TJs), reducing BSCB permeability and subsequently inhibiting inflammation and apoptosis. Ultimately, this led to enhanced neural regeneration and functional recovery. Further experiments revealed that the RhoA/Rock1/P-MLC pathway plays a key role in the effects of Mertk. These findings highlight the role of Mertk in promoting SCI recovery through its ability to mitigate BSCB permeability and may provide potential targets for SCI repair.

Fasudil-modified macrophages reduce inflammation and regulate the immune response in experimental autoimmune encephalomyelitis

Multiple sclerosis is characterized by demyelination and neuronal loss caused by inflammatory cell activation and infiltration into the central nervous system. Macrophage polarization plays an important role in the pathogenesis of experimental autoimmune encephalomyelitis, a traditional experimental model of multiple sclerosis. This study investigated the effect of Fasudil on macrophages and examined the therapeutic potential of Fasudil-modified macrophages in experimental autoimmune encephalomyelitis. We found that Fasudil induced the conversion of macrophages from the pro-inflammatory M1 type to the anti-inflammatory M2 type, as shown by reduced expression of inducible nitric oxide synthase/nitric oxide, interleukin-12, and CD16/32 and increased expression of arginase-1, interleukin-10, CD14, and CD206, which was linked to inhibition of Rho kinase activity, decreased expression of toll-like receptors, nuclear factor-κB, and components of the mitogen-activated protein kinase signaling pathway, and generation of the pro-inflammatory cytokines tumor necrosis factor-α, interleukin-1β, and interleukin-6. Crucially, Fasudil-modified macrophages effectively decreased the impact of experimental autoimmune encephalomyelitis, resulting in later onset of disease, lower symptom scores, less weight loss, and reduced demyelination compared with unmodified macrophages. In addition, Fasudil-modified macrophages decreased interleukin-17 expression on CD4+ T cells and CD16/32, inducible nitric oxide synthase, and interleukin-12 expression on F4/80+ macrophages, as well as increasing interleukin-10 expression on CD4+ T cells and arginase-1, CD206, and interleukin-10 expression on F4/80+ macrophages, which improved immune regulation and reduced inflammation. These findings suggest that Fasudil-modified macrophages may help treat experimental autoimmune encephalomyelitis by inducing M2 macrophage polarization and inhibiting the inflammatory response, thereby providing new insight into cell immunotherapy for multiple sclerosis.

Zinc as a Mediator Through the ROCK1 Pathway of Cognitive Impairment in Aluminum-Exposed Workers: A Clinical and Animal Study

Aluminum (Al) exposure was implicated in neurodegenerative diseases and cognitive impairment, yet the involvement of zinc (Zn) and its mechanism in Al-induced mild cognitive impairment (MCI) remains poorly understood. The objective is to explore the role of Zn in Al-induced cognitive impairment and its potential mechanisms. Montreal cognitive assessment (MoCA) test scores and serum Al, Zn from Al industry workers were collected. A mediation analysis was performed to evaluate the role of serum Zn among serum Al and MoCA test scores. Subsequently, an Al-exposure study was conducted on a rat model categorized into control, low-, medium-, and high-dose groups. After a Morris Water Maze test and detection of Al, Zn content in the hippocampus, integrated transcriptomic and proteomic analyses between the control group and the high-dose group were performed to identify the differentially expressed genes (DEPs), proteins (DEPs), and pathways. To corroborate these findings, quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting (WB) were selected to identify the gene and protein results. Zn overall mediates the relationship between serum Al and cognitive function (mediation effect 17.82%, effect value =  - 0.0351). In the Al-exposed rat model, 734 DEGs, 18 miRNAs, 35 lncRNAs, 64 circRNAs, and 113 DEPs were identified between the high-dose group and the control group. Among them, ROCK1, DMD, and other four DEPs were identified as related to zinc finger proteins (ZNF). Co-enrichment analyses of the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) linked these changes to the RHOA/ROCK1 signaling axis. ZNF-related proteins Rock1, DMD, and DHX57 in the high-dose group were downregulated (p = 0.006, 0.003, 0.04), and the expression of Myl9, Rhoa, miR431, and miR182 was also downregulated (p = 0.003, 0.032, 0.032, and 0.046). These findings also show correlations between Al, Zn levels in the hippocampus, water maze performance, and expressions of Myl9, Rhoa, miR431, miR182, DMD, ROCK1, and DHX57, with both negative and positive associations. Based on the results, we determined that Zn was involved in Al-induced MCI in Al workers and Al-exposed rat models. Al exposure and interaction with Zn could trigger the downregulation of ZNF of ROCK1, DMD, and DHX57. miR431, miR182 regulate RHOA/ROCK1 was one of the Zn-involved pathways in Al-induced cognitive impairment.

Injury to Cone Synapses by Retinal Detachment: Differences from Rod Synapses and Protection by ROCK Inhibition

Attachment of a detached retina does not always restore vision to pre-injury levels, even if the attachment is anatomically successful. The problem is due in part to long-term damage to photoreceptor synapses. Previously, we reported on damage to rod synapses and synaptic protection using a Rho kinase (ROCK) inhibitor (AR13503) after retinal detachment (RD). This report documents the effects of detachment, reattachment, and protection by ROCK inhibition on cone synapses. Conventional confocal and stimulated emission depletion (STED) microscopy were used for morphological assessment and electroretinograms for functional analysis of an adult pig model of RD. RDs were examined 2 and 4 h after injury or two days later when spontaneous reattachment had occurred. Cone pedicles respond differently than rod spherules. They lose their synaptic ribbons, reduce invaginations, and change their shape. ROCK inhibition protects against these structural abnormalities whether the inhibitor is applied immediately or 2 h after the RD. Functional restoration of the photopic b-wave, indicating cone-bipolar neurotransmission, is also improved with ROCK inhibition. Successful protection of both rod and cone synapses with AR13503 suggests this drug will (1) be a useful adjunct to subretinal administration of gene or stem cell therapies and (2) improve recovery of the injured retina when treatment is delayed.

Saikosaponin d (SSD) alleviates diabetic peripheral neuropathy by regulating the AQP1/RhoA/ROCK signaling in streptozotocin-induced diabetic rats

AIMS

Diabetic peripheral neuropathy (DPN) is one of the most important complications of diabetes with a poor prognosis. Saikosaponin d (SSD) is a triterpenoid saponin isolated from Radix Bupleuri that has multiple pharmacological activities. However, whether SSD affects DPN is unclarified.

METHODS

Sprague Dawley rats were treated with streptozotocin (STZ) and high-fat diet (HFD) to induce DPN, in the presence or absence of SSD, with or without transfection of lentivirus vectors carrying siRNA targeting aquaporin 1 (si-AQP1). The body weight, plasma glucose levels, mechanical and thermal hyperalgesia, and nerve conductive velocity (NCV) of rats were measured. Hematoxylin-Eosin staining was used for histopathological observation of sciatic nerves. RT-qPCR and western blotting were utilized for measuring expression levels of AQP1 and ras homolog family member A/Rho-associated protein kinase (RhoA/ROCK) signaling pathway-related markers in dorsal root ganglion (DRG) of rats.

RESULTS

SSD increased the body weight, decreased plasma glucose levels, attenuated mechanical and thermal hyperalgesia, enhanced NCV and reduced proinflammatory cytokine levels in DPN rats. AQP1 displayed a high level in DPN rats and SSD treatment repressed the expression of AQP1. SSD enhanced the protective effect of AQP1 knockdown on the pathological changes of DPN. AQP1 depletion suppressed the activation of RhoA/ROCK signaling pathway in DPN rats.

CONCLUSION

SSD alleviates STZ/HFD-induced DPN in rats by inhibiting the AQP1/RhoA/ROCK signaling pathway.

A focus on Rho/ROCK signaling pathway: An emerging therapeutic target in depression

Depression is the most common mental health disorder worldwide; however, the exact cellular and molecular mechanisms of this major depressive disorder are unclear so far. Experimental studies have demonstrated that depression is associated with significant cognitive impairment, dendrite spine loss, and reduction in connectivity among neurons that contribute to symptoms associated with mood disorders. Rho/Rho-associated coiled-coil containing protein kinase (ROCK) receptors are exclusively expressed in the brain and Rho/ROCK signaling has gained considerable attention as it plays a crucial role in the development of neuronal architecture and structural plasticity. Chronic stress-induced activation of the Rho/ROCK signaling pathway promotes neuronal apoptosis and loss of neural processes and synapses. Interestingly, accumulated evidence has identified Rho/ROCK signaling pathways as a putative target for treating neurological disorders. Furthermore, inhibition of the Rho/ROCK signaling pathway has proven to be effective in different models of depression, which signify the potential benefits of clinical Rho/ROCK inhibition. The ROCK inhibitors extensively modulate antidepressant-related pathways which significantly control the synthesis of proteins, and neuron survival and ultimately led to the enhancement of synaptogenesis, connectivity, and improvement in behavior. Therefore, the present review refines the prevailing contribution of this signaling pathway in depression and highlighted preclinical shreds of evidence for employing ROCK inhibitors as disease-modifying targets along with possible underlying mechanisms in stress-associated depression.

Somatic A-to-I RNA-edited RHOA isoform 2 specific-R176G mutation promotes tumor progression in lung adenocarcinoma

Adenosine-to-inosine (A-to-I) RNA editing is the most common posttranscriptional editing to create somatic mutations and increase proteomic diversity. However, the functions of the edited mutations are largely underexplored. To identify novel targets in lung adenocarcinoma (LUAD), we conducted a genome-wide somatic A-to-I RNA editing analysis of 23 paired adjacent normal and LUAD transcriptomes and identified 26,280 events, including known nonsynonymous AZIN1-S367G and novel RHOAiso2 (RHOA isoform 2)-R176G, tubulin gamma complex associated protein 2 (TUBGCP2)-N211S, and RBMXL1-I40 M mutations. We validated the edited mutations in silico in multiple databases and in newly collected LUAD tissue pairs with the SEQUENOM MassARRAY® and TaqMan PCR Systems. We selected RHOAiso2-R176G due to its significant level, isoform-specificity, and being the most common somatic edited nonsynonymous mutation of RHOAiso2 to investigate its roles in LUAD tumorigenesis. RHOAiso2 is a ubiquitous but low-expression alternative spliced isoform received a unique Alu-rich exon at the 3' RHOA mRNA to become an editing RNA target, leading to somatic hypermutation and protein diversity. Interestingly, LUAD patients harboring the RHOAiso2-R176G mutation were associated with aberrant RHOA functions, cancer cell proliferation and migration, and poor clinical outcomes in transcriptome analysis. Mechanistically, RHOAiso2-R176G mutation-expressing LUAD cells potentiate RHOA-guanosine triphosphate (GTP) activity to phosphorylate ROCK1/2 effectors and enhance cell proliferation and migration in vitro and increase tumor growth in xenograft and systemic metastasis models in vivo. Taken together, the RHOAiso2-R176G mutation is a common somatic A-to-I edited mutation of the hypermutated RHOA isoform 2. It is an oncogenic and isoform-specific theranostic target that activates RHOA-GTP/p-ROCK1/2 signaling to promote tumor progression.

OMICS Analyses Unraveling Related Gene and Protein-Driven Molecular Mechanisms Underlying PACAP 38-Induced Neurite Outgrowth in PC12 Cells

The study aimed to understand mechanism/s of neuronal outgrowth in the rat adrenal-derived pheochromocytoma cell line (PC12) under pituitary adenylate cyclase-activating polypeptide (PACAP) treatment. Neurite projection elongation was suggested to be mediated via Pac1 receptor-mediated dephosphorylation of CRMP2, where GSK-3β, CDK5, and Rho/ROCK dephosphorylated CRMP2 within 3 h after addition of PACAP, but the dephosphorylation of CRMP2 by PACAP remained unclear. Thus, we attempted to identify the early factors in PACAP-induced neurite projection elongation via omics-based transcriptomic (whole genome DNA microarray) and proteomic (TMT-labeled liquid chromatography-tandem mass spectrometry) analyses of gene and protein expression profiles from 5-120 min after PACAP addition. The results revealed a number of key regulators involved in neurite outgrowth, including known ones, called 'Initial Early Factors', e.g., genes Inhba, Fst, Nr4a1,2,3, FAT4, Axin2, and proteins Mis12, Cdk13, Bcl91, CDC42, including categories of 'serotonergic synapse, neuropeptide and neurogenesis, and axon guidance'. cAMP signaling and PI3K-Akt signaling pathways and a calcium signaling pathway might be involved in CRMP2 dephosphorylation. Cross-referencing previous research, we tried to map these molecular components onto potential pathways, and we may provide important new information on molecular mechanisms of neuronal differentiation induced by PACAP. Gene and protein expression data are publicly available at NCBI GSE223333 and ProteomeXchange, identifier PXD039992.

Inhibition of Rho-kinase ameliorates decreased spine density in the medial prefrontal cortex and methamphetamine-induced cognitive dysfunction in mice carrying schizophrenia-associated mutations of the Arhgap10 gene

Copy-number variations in the ARHGAP10 gene encoding Rho GTPase-activating protein 10 are associated with schizophrenia. Model mice (Arhgap10 S490P/NHEJ mice) that carry "double-hit" mutations in the Arhgap10 gene mimic the schizophrenia in a Japanese patient, exhibiting altered spine density, methamphetamine-induced cognitive dysfunction, and activation of RhoA/Rho-kinase signaling. However, it remains unclear whether the activation of RhoA/Rho-kinase signaling due to schizophrenia-associated Arhgap10 mutations causes the phenotypes of these model mice. Here, we investigated the effects of fasudil, a brain permeable Rho-kinase inhibitor, on altered spine density in the medial prefrontal cortex (mPFC) and on methamphetamine-induced cognitive impairment in a touchscreen‑based visual discrimination task in Arhgap10 S490P/NHEJ mice. Fasudil (20 mg/kg, intraperitoneal) suppressed the increased phosphorylation of myosin phosphatase-targeting subunit 1, a substrate of Rho-kinase, in the striatum and mPFC of Arhgap10 S490P/NHEJ mice. In addition, daily oral administration of fasudil (20 mg/kg/day) for 7 days ameliorated the reduced spine density of layer 2/3 pyramidal neurons in the mPFC. Moreover, fasudil (3-20 mg/kg, intraperitoneal) rescued the methamphetamine (0.3 mg/kg)-induced cognitive impairment of visual discrimination in Arhgap10 S490P/NHEJ mice. Our results suggest that Rho-kinase plays significant roles in the neuropathological changes in spine morphology and in the vulnerability of cognition to methamphetamine in mice with schizophrenia-associated Arhgap10 mutations.

Current Pharmacotherapy and Multi-Target Approaches for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by decreased synaptic transmission and cerebral atrophy with appearance of amyloid plaques and neurofibrillary tangles. Cognitive, functional, and behavioral alterations are commonly associated with the disease. Different pathophysiological pathways of AD have been proposed, some of which interact and influence one another. Current treatment for AD mainly involves the use of therapeutic agents to alleviate the symptoms in AD patients. The conventional single-target treatment approaches do not often cause the desired effect in the disease due to its multifactorial origin. Thus, multi-target strategies have since been undertaken, which aim to simultaneously target multiple targets involved in the development of AD. In this review, we provide an overview of the pathogenesis of AD and the current drug therapies for the disease. Additionally, rationales of the multi-target approaches and examples of multi-target drugs with pharmacological actions against AD are also discussed.

Low and high dose methamphetamine differentially regulate synaptic structural plasticity in cortex and hippocampus

Psychostimulants, such as methamphetamine (METH) can induce structural remodeling of synapses by remodeling presynaptic and postsynaptic morphology. Escalating or long-lasting high dose METH accounts for neurodegeneration by targeting multiple neurotransmitters. However, the effects of low dose METH on synaptic structure and the modulation mechanism remain elusive. This study aims to assess the effects of low dose (2 mg/kg) and high dose (10 mg/kg) of METH on synaptic structure alternation in hippocampus and prefrontal cortex (PFC) and to reveal the underlying mechanism involved in the process. Low dose METH promoted spine formation, synaptic number increase, post-synaptic density length elongation, and memory function. High dose of METH induced synaptic degeneration, neuronal number loss and memory impairment. Moreover, high dose, but not low dose, of METH caused gliosis in PFC and hippocampus. Mechanism-wise, low dose METH inactivated ras-related C3 botulinum toxin substrate 1 (Rac1) and activated cell division control protein 42 homolog (Cdc42); whereas high dose METH inactivated Cdc42 and activated Rac1. We provided evidence that low and high doses of METH differentially regulate synaptic plasticity in cortex and hippocampus.

Unveiling the Multitarget Anti-Alzheimer Drug Discovery Landscape: A Bibliometric Analysis

Multitarget anti-Alzheimer agents are the focus of very intensive research. Through a comprehensive bibliometric analysis of the publications in the period 1990-2020, we have identified trends and potential gaps that might guide future directions. We found that: (i) the number of publications boomed by 2011 and continued ascending in 2020; (ii) the linked-pharmacophore strategy was preferred over design approaches based on fusing or merging pharmacophores or privileged structures; (iii) a significant number of in vivo studies, mainly using the scopolamine-induced amnesia mouse model, have been performed, especially since 2017; (iv) China, Italy and Spain are the countries with the largest total number of publications on this topic, whereas Portugal, Spain and Italy are the countries in whose scientific communities this topic has generated greatest interest; (v) acetylcholinesterase, β-amyloid aggregation, oxidative stress, butyrylcholinesterase, and biometal chelation and the binary combinations thereof have been the most commonly pursued, while combinations based on other key targets, such as tau aggregation, glycogen synthase kinase-3β, NMDA receptors, and more than 70 other targets have been only marginally considered. These results might allow us to spot new design opportunities based on innovative target combinations to expand and diversify the repertoire of multitarget drug candidates and increase the likelihood of finding effective therapies for this devastating disease.