MiR-34a Regulates Axonal Growth of Dorsal Root Ganglia Neurons by Targeting FOXP2 and VAT1 in Postnatal and Adult Mouse

Non-coding RNAs in diabetic peripheral neuropathy: their role and mechanisms underlying their effects

Diabetic peripheral neuropathy (DPN) is a complication of diabetes with a high rate of disability. However, current clinical treatments for DPN are suboptimal. Non-coding RNAs (ncRNAs) are a type of RNAs that are not translated into proteins. NcRNAs perform functions that regulate epigenetic modifications, transcriptional or post-transcriptional regulators of proteins, and thus participate in the physiological and pathological processes of the body. NcRNAs play a role in the progress of DPN by affecting the processes of inflammation, oxidative stress, cellular autophagy or apoptosis. Therefore, ncRNAs treatment is regarded as a promising therapeutic approach for DPN. In addition, since some ncRNAs present stably in the blood of DPN patients, they are considered as potential biomarkers that contribute to early clinical diagnosis. In this paper, we review the studies on the role of ncRNAs in DPN in the last decade, and discuss the mechanisms of ncRNAs, aiming to provide a reference for the future research on the treatment and early diagnosis of DPN.

Long Non-coding RNA ANRIL and Its Role in the Development of Age-Related Diseases

ANRIL is known as a lncRNA that has many linear and circular isoforms and its polymorphisms are observed to be associated with the pathogenesis of many diseases including age-related diseases. Age-related diseases including atherosclerosis, ischemic heart disease, and Alzheimer's and Parkinson's disease are the most common cause of mortality in both developed and undeveloped countries and that is why a better understanding of their pathogenesis and underlying mechanisms is necessary for controlling their healthcare burden.In this review, we aim to gather the data of researches which have investigated the role of ANRIL in aging and its related diseases. The conclusions of this paper might give a new insight for decreasing the mortality rate of these diseases.

Dexmedetomidine alleviates oxidative stress and mitochondrial dysfunction in diabetic peripheral neuropathy via the microRNA-34a/SIRT2/S1PR1 axis

OBJECTIVE

Dexmedetomidine (Dex) is a highly selective α₂-adrenoceptor agonist with sedative, analgesic, sympatholytic, and hemodynamic-stabilizing properties, which plays a neuroprotective role in diabetic peripheral neuropathy (DPN) and diabetes-induced nerve damage. However, the related molecular mechanisms are not fully understood. Therefore, our study explored the mechanism of Dex in DPN using rat and RSC96 cell models.

METHODS

Sciatic nerve sections were observed under an optical microscope and the ultrastructure of the sciatic nerves was observed under a transmission electron microscope. Oxidative stress was assessed by detecting MDA, SOD, GSH-Px, and ROS levels. The motor nerve conduction velocity (MNCV), mechanical withdrawal threshold (MWT), and thermal withdrawal latency (TWL) of rats were measured. Cell viability, apoptosis, and the changes in the expression of related genes and proteins were examined. Furthermore, the relationship between microRNA (miR)-34a and SIRT2 or SIRT2 and S1PR1 was analyzed.

RESULTS

Dex reversed DPN-induced decreases in MNCV, MWT, and TWL. Dex alleviated oxidative stress, mitochondrial damage, and apoptosis in both the rat and RSC96 cell models of DPN. Mechanistically, miR-34a negatively targeted SIRT2, and SIRT2 inhibited S1PR1 transcription. The overexpression of miR-34a or S1PR1 or the inhibition of SIRT2 counteracted the neuroprotective effects of Dex in DPN in vivo and in vitro.

CONCLUSION

Dex alleviates oxidative stress and mitochondrial dysfunction associated with DPN by downregulating miR-34a to regulate the SIRT2/S1PR1 axis.

Icariin inhibits epithelial mesenchymal transition of renal tubular epithelial cells via regulating the miR-122-5p/FOXP2 axis in diabetic nephropathy rats

Epithelial mesenchymal transition (EMT) of renal tubular epithelial cells (RTECs) dominates the pathology of diabetic nephropathy (DN). microRNAs (miRNAs) can influence the fate of DN via regulation of EMT. This study aimed to analyze the role of Icariin (ICA) in EMT of RTECs, hoping to provide theoretical basis for DN management. The DN rat model was established using streptozocin, followed by ICA treatment, histopathological observation, and detection of creatinine and blood urea nitrogen. In vitro cell models were established using high glucose (HG), followed by assessment of cell proliferation, apoptosis, and migration, and E-cadherin, α-SMA, miR-122-5p, and FOXP2 expressions. Cells were transfected with miR-122-5p mimics or si-FOXP2 for joint experiments with ICA. The targeting relationship between miR-122-5p and FOXP2 was verified. ICA repaired renal dysfunctions and glomerular structure abnormities of DN rats in a dose-dependent manner. In vitro, ICA improved proliferation while suppressed migration, apoptosis, and EMT of RTECs. miR-122-5p was up-regulated in DN rats and suppressed by ICA, and miR-122-5p targeted FOXP2. miR-122-5p up-regulation or FOXP2 down-regulation reversed the protective effects of ICA on HG-induced RTECs. Overall, our finding ascertained that ICA inhibited miR-122-5p to promote FOXP2 transcription, thereby attenuating EMT of RTECs and renal injury in DN rats.

miR-134-5p promotes inflammation and apoptosis of trophoblast cells via regulating FOXP2 transcription in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a prevalent and risky pregnant complication which warrants targeted therapy for restriction the inflammation and apoptosis of trophoblast cells. This study sought to analyze the aberrant expression and regulatory mechanism of microRNA (miR)-134-5p in GDM. The miR-134-5p expression in the serum of GDM patients and normal participants was detected via qRT-PCR, followed by receiver operating characteristic (ROC) curve analysis. In vitro GDM cell model was established in the HTR-8/SVneo cells using 25 mmol/L glucose, followed by transfection with miR-134-5p inhibitor and si-Forkhead box p2(FOXP2). The miR-134-5p and FOXP2 expressions, TNF-α, IL-1β, and IL-10 levels, cell proliferation, migration, and apoptosis were determined by a combination of qRT-PCR, western blot, ELISA, and cell counting Kit-8, Transwell assay, and flow cytometry. The binding relationship between miR-134-5p and FOXP2 was predicted and verified. Our results revealed that miR-134-5p was increased in the serum of GDM patients and could serve as a critical diagnostic marker for GDM. Moreover, miR-134-5p was upregulated in the high glucose (HG)-induced HTR-8/SVneo cells. The miR-134-5p inhibition suppressed the inflammation and apoptosis of HG-induced HTR-8/SVneo cells. miR-134-5p inhibited FOXP2 expression. FOXP2 expression was decreased in GDM. FOXP2 inhibition attenuated the function of miR-134-5p in HG-induced HTR-8/SVneo cells. Overall, miR-134-5p inhibited the FOXP2 expression to facilitate the inflammation and apoptosis of trophoblast cells, thereby exacerbating GDM.

Long non-coding RNA ANRIL interacts with microRNA-34a and microRNA-125a, and they all correlate with disease risk and severity of Parkinson's disease

BACKGROUND

This study aimed to investigate the correlation of long non-coding RNA antisense non-coding RNA in the INK4 locus (lncRNA ANRIL) and its target microRNAs (microRNA-34a (miR-34a) and microRNA-125a (miR-125a)) with disease risk and severity of Parkinson's disease (PD).

METHODS

Seventy-eight PD patients and 78 age-/gender-matched controls were consecutively enrolled. Their peripheral blood mononuclear cell samples were collected and proposed for the reverse-transcription quantitative polymerase chain reaction to complete lncRNA ANRIL, miR-34a, and miR-125a measurements.

RESULTS

LncRNA ANRIL was upregulated, while miR-34a and miR-125a were downregulated in PD patients compared to controls (all p < 0.001). Further, they all showed certain values for PD risk identification by ROC curve analyses, among which lncRNA ANRIL showed the highest AUC (AUC: 0.879, 95% CI: 0.824-0.934). Furthermore, lncRNA ANRIL negatively correlated with miR-34a (p = 0.016) and miR-125a (p = 0.005) in PD patients, but not in controls. In addition, lncRNA ANRIL was observed to positively associate with UPDRS-I score (p = 0.029), UPDRS-III score (p = 0.006), and UPDRS-IV score (p = 0.033), while negatively correlated with MMSE score (p = 0.003). These associations were less distinct as to miR-34a and miR-125a.

CONCLUSION

LncRNA ANRIL interacts with miR-34a and miR-125a in PD patients, and they all correlate with disease risk and severity of PD.

Paeoniflorin Effect of Schwann Cell-Derived Exosomes Ameliorates Dorsal Root Ganglion Neurons Apoptosis through IRE1α Pathway

Background

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes but its pathogenesis is not fully clarified. Endoplasmic reticulum (ER) stress has been confirmed to be involved in the development of DPN. Dorsal root ganglion neuron (DRGn) is the target cell of DPN injure in the peripheral neurons system. Schwann cell (SCs)-derived exosomes (SC-EXOs) can carry IRE1α signal transduction factors in ER stress to DRGn. The aim of this study is to investigate the effect of SC-EXOs treated with paeoniflorin (PF) on DRGn stimulated by high glucose.

Methods

SCs were divided into Control group (Control), 150 mM glucose group (HG), high osmotic pressure group (HOP), and low, middle, and high dose PF group (PF1, PF10, and PF100). Exosomes were obtained from SCs by ultracentrifugation and identified according to marker proteins, including CD63, Alix, Hsp70, and TSG101. ER stress initiating factor GRP78, the IRE1α pathway information transmission factor IRE1α, and the phosphorylation level of IRE1α were detected by Western blot, DRGn is divided into Control group (Control), 50 mM glucose group + Control exosomes group (HG + EXOs Control), 50 mM glucose group (HG), and 50 mM glucose group + administration exosomes group (HG + EXOs PF1, HG + EXOs PF10, and HG + EXOs PF100); ER morphology of primary DRGn was observed by using the transmission electron microscope, the level of DRGn apoptosis was analyzed by TUNEL, and the downstream proteins of ER stress including CHOP, XBP1S, JNK, and p-JNK in DRG and the expression of apoptosis-related proteins Bcl-2, Bax, Caspase-3, and Caspase-12 were measured by Western blot.

Results

Compared with the exosomes in the HG group, the exosomes after the intervention of PF can significantly reduce the expression of GRP78, IRE1α, and the phosphorylation level of IRE1α(P < 0.05); compared with the DRGn in the HG group, the SC-EXOs treated with PF could regulate the expression of proteins downstream of IRE1α pathway in ER stress (P < 0.05 or P < 0.01), improve the morphological integrity of ER, and reduce apoptosis in DRGn (P < 0.05 or P < 0.01).

Conclusion

PF regulates the information of ER stress carried by SC-EXOs and further affects downstream of IRE1α pathway in DRGn, thus reducing ER stress-induced apoptosis. PF can interfere with DPN through affecting information communication carried by EXOs between SCs and DRGn.

Programmable dual responsive system reconstructing nerve interaction with small-diameter tissue-engineered vascular grafts and inhibiting intimal hyperplasia in diabetes

Small-diameter tissue-engineered vascular grafts (sdTEVGs) with hyperglycemia resistance have not been constructed. The intimal hyperplasia caused by hyperglycemia remains problem to hinder the patency of sdTEVGs. Here, inspired by bionic regulation of nerve on vascular, we found the released neural exosomes could inhibit the abnormal phenotype transformation of vascular smooth muscle cells (VSMCs). The transformation was a prime culprit causing the intimal hyperplasia of sdTEVGs. To address this concern, sdTEVGs were modified with an on-demand programmable dual-responsive system of ultrathin hydrogels. An external primary Reactive Oxygen Species (ROS)-responsive Netrin-1 system was initially triggered by local inflammation to induce nerve remolding of the sdTEVGs overcoming the difficulty of nerve regeneration under hyperglycemia. Then, the internal secondary ATP-responsive DENND1A (guanine nucleotide exchange factor) system was turned on by the neurotransmitter ATP from the immigrated nerve fibers to stimulate effective release of neural exosomes. The results showed nerve fibers grow into the sdTEVGs in diabetic rats 30 days after transplantation. At day 90, the abnormal VSMCs phenotype was not detected in the sdTEVGs, which maintained long-time patency without intima hyperplasia. Our study provides new insights to construct vascular grafts resisting hyperglycemia damage.

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VSMCs undergo a phenotypic transformation under high glucose, which lead to intimal hyperplasia in sdTEVGs.

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Neural exosomes could inhibit the abnormal phenotype transformation of VSMCs from contractile to synthetic.

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SdTEVGs with on-demand programmable dual responsive system inhibited intimal hyperplasia in diabetes.

A Rare Variation in the 3' Untranslated Region of the Presenilin 2 Gene Is Linked to Alzheimer's Disease

Rare variations in coding regions may alter the amino acid sequence and function of presenilins (PSENs), which results in the dysfunction of gamma-secretase, in turn contributing to the development of familial Alzheimer's disease (AD). However, whether rare variations in the 3' untranslated region (UTR) may change the expression level of PSEN2 leading to AD remains unclear. In a familial AD pedigree, DNA samples of the patients were screened for APP, PSEN1, and PSEN2 gene mutations using Sanger sequencing. Allele A of rs537889666, a rare variation located in the 3' UTR of PSEN2, was found in all AD patients, but not in the healthy control in the family. Cosegregation analysis (n = 5) revealed that allele A of rs537889666 may be a pathogenic rare variation. The dual-luciferase assay revealed that allele A suppressed the combination of miR-183-5p and the 3' UTR of PSEN2, which may block the miR-183-5p-mediated suppression of PSEN2 expression. Further study showed an elevated ratio of Aβ42/40 under overexpressed PSEN2 conditions. Measurements of the cerebrospinal fluid showed that PSEN2 levels were increased in both sporadic and AD in this family, suggesting that elevated PSEN2 was associated with the disease. In addition, the miR-183-5p inhibitor or mimic can increase or decrease Aβ42/40 ratios. In conclusion, the results indicate that allele A of rs537889666 upregulated PSEN2 levels, increasing the Aβ42/40 ratio and contributing to AD development.

Small extracellular vesicles ameliorate peripheral neuropathy and enhance chemotherapy of oxaliplatin on ovarian cancer

There are no effective treatments for chemotherapy induced peripheral neuropathy (CIPN). Small extracellular vesicles (sEVs) facilitate intercellular communication and mediate nerve function and tumour progression. We found that the treatment of mice bearing ovarian tumour with sEVs derived from cerebral endothelial cells (CEC-sEVs) in combination with a chemo-drug, oxaliplatin, robustly reduced oxaliplatin-induced CIPN by decreasing oxaliplatin-damaged myelination and nerve fibres of the sciatic nerve and significantly amplified chemotherapy of oxaliplatin by reducing tumour size. The combination therapy substantially increased a set of sEV cargo-enriched miRNAs, but significantly reduced oxaliplatin-increased proteins in the sciatic nerve and tumour tissues. Bioinformatics analysis revealed the altered miRNAs and proteins formed two distinct networks that regulate neuropathy and tumour growth, respectively. Intravenously administered CEC-sEVs were internalized by axons of the sciatic nerve and cancer cells. Reduction of CEC-sEV cargo miRNAs abolished the effects of CEC-sEVs on oxaliplatin-inhibited axonal growth and on amplification of the anti-cancer effect in ovarian cancer cells, suggesting that alterations in the networks of miRNAs and proteins in recipient cells contribute to the therapeutic effect of CEC-sEVs on CIPN. Together, the present study demonstrates that CEC-sEVs suppressed CIPN and enhanced chemotherapy of oxaliplatin in the mouse bearing ovarian tumour.

Emerging Roles of microRNAs as Biomarkers and Therapeutic Targets for Diabetic Neuropathy

Diabetic neuropathy (DN) is the most prevalent chronic complication of diabetes mellitus. The exact pathophysiological mechanisms of DN are unclear; however, communication network dysfunction among axons, Schwann cells, and the microvascular endothelium likely play an important role in the development of DN. Mounting evidence suggests that microRNAs (miRNAs) act as messengers that facilitate intercellular communication and may contribute to the pathogenesis of DN. Deregulation of miRNAs is among the initial molecular alterations observed in diabetics. As such, miRNAs hold promise as biomarkers and therapeutic targets. In preclinical studies, miRNA-based treatment of DN has shown evidence of therapeutic potential. But this therapy has been hampered by miRNA instability, targeting specificity, and potential toxicities. Recent findings reveal that when packaged within extracellular vesicles, miRNAs are resistant to degradation, and their delivery efficiency and therapeutic potential is markedly enhanced. Here, we review the latest research progress on the roles of miRNAs as biomarkers and as potential clinical therapeutic targets in DN. We also discuss the promise of exosomal miRNAs as therapeutics and provide recommendations for future research on miRNA-based medicine.

mRNA expression profile analysis reveals a C-MYC/miR-34a pathway involved in the apoptosis of diffuse large B-cell lymphoma cells induced by Yiqichutan treatment

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of adult non-Hodgkin's lymphoma (NHL). While DLBCL is sensitive to chemotherapy, a certain percentage of patients with DLBCL experience relapse. Previous studies have indicated that Yiqichutan treatment, which was developed to treat NHL, can inhibit DLBCL cell growth, but the mechanism is not fully understood. The present study identified 991 differentially expressed mRNAs, with 498 upregulated and 493 downregulated (P<0.05), in SUDHL-6 cells exposed to Yiqichutan. The underlying pathways included the Jak/Stat and PI3K signaling pathways. In total, six representative mRNAs were selected for validation with reverse transcription-quantitative PCR (RT-qPCR), and a strong correlation was identified between the RT-qPCR results and microarray data. Since the transcription factor C-MYC is involved in both the Jak/Stat and PI3K signaling pathways, C-MYC and its associated microRNA (miR) were selected for further analysis. It was found that knockdown of C-MYC increased miR-34a expression levels, inhibited forkhead box P1 (Foxp1) expression levels and promoted DLBCL cell apoptosis. In addition, the miR-34a mimics further enhanced the role of C-MYC knockdown. It was demonstrated that, the expression levels of apoptotic factors Bax and poly (ADP-ribose) polymerase were significantly upregulated with C-MYC knockdown and miR-34a mimics in SUDHL-6 cells, while the Bcl2 expression level was significantly reduced. Moreover, Yiqichutan treatment increased miR-34a expression levels and induced apoptosis, as well as reducing Foxp1 expression level in SUDHL-6 cells. Therefore, the present results suggested that Yiqichutan treatment affected DLBCL cells via several signaling pathways. Furthermore, Yiqichutan may inhibit the proliferation of DLBCL cells by blocking the C-MYC/miR-34a signaling pathway.

MicroRNA‑29a promotes the neural differentiation of rat neural stem/progenitor cells by targeting KLF4

Neural stem/progenitor cells (NSPCs) remain in the mammalian brain throughout life, where they have the ability to self-renew and generate different types of cell in the central nervous system (CNS). Therefore, NSPCs may be a potential novel therapeutic strategy following damage to the CNS. Previous research has reported that microRNA (miR)-29a served an important role in regulating cell proliferation, differentiation and survival; however, to the best of our knowledge, little is known of the effect of miR-29a in neural differentiation. The present study aimed to investigate the effect of miR-29a on the differentiation of NSPCs, determined via RNA interference, immunostaining, reverse transcription-quantitative PCR and western blotting. The present study discovered that the expression levels of miR-29a were significantly upregulated in a time-dependent manner during neural differentiation. Immunostaining showed that overexpression of miR-29a promoted neural differentiation, which manifested in increased expression levels of neuron-specific class III β-tubulin (Tuj1); however, miR-29a had no effect on neuroglial differentiation. The expression levels of Kruppel-like factor 4 (KLF4) were downregulated following overexpression of miR-29a, whereas the inhibition of miR-29a demonstrated the opposite effect. These results suggested that the overexpression of miR-29a may promote neural differentiation in cultured rat NSPCs by decreasing the expression levels of KLF4. Thus indicating that targeting KLF4, a crucial regulatory factor for the maintenance of stemness, may be a potential underlying mechanism of action for miR-29a. In conclusion, the findings of the present study identified a potential mechanism of action for miR-29a in NSPC differentiation and provided a novel insight into the treatment strategies for CNS damage.

Vaccarin Regulates Diabetic Chronic Wound Healing through FOXP2/AGGF1 Pathways

Background: Diabetes mellitus is a growing global health issue nearly across the world. Diabetic patients who are prone to develop diabetes-related complications often exhibit progressive neuropathy (painless and sensory loss). It is usual for small wounds to progress to ulceration, which especially worsens with peripheral arterial disease and in the presence of anaerobic bacteria, culminating into gangrene. In our study, vaccarin (VAC), the main active monomer extracted from Chinese herb vaccariae semen, is proven to have a role in promoting diabetic chronic wound healing through a cytoprotective role under high glucose conditions. Materials and methods: We constructed a pressure ulcer on both VAC-treated and control mice based on a type 1 diabetes (T1DM) model. The wound healing index was evaluated by an experimental wound assessment tool (EWAT). We also determined the effect of VAC on the proliferation and cell migration of human microvascular endothelial cells (HMEC-1) by a cell counting kit (CCK-8), a scratch and transwell assay. Results: The results demonstrated that VAC could promote the proliferation and migration of high glucose-stimulated HMEC-1 cells, which depend on the activation of FOXP2/AGGF1. Activation of the angiogenic factor with G patch and FHA domains 1 (AGGF1) caused enhanced phosphorylation of serine/threonine kinase (Akt) and extracellular regulated protein kinases (Erk1/2). By silencing the expression of forkhead box p2 (FOXP2) protein by siRNA, both mRNA and protein expression of AGGF1 were downregulated, leading to a decreased proliferation and migration of HMEC-1 cells. In addition, a diabetic chronic wound model in vivo unveiled that VAC had a positive effect on chronic wound healing, which involved the activation of the above-mentioned pathways. Conclusions: In summary, our study found that VAC promoted chronic wound healing in T1DM mice by activating the FOXP2/AGGF1 pathway, indicating that VAC may be a promising candidate for the treatment of the chronic wounds of diabetic patients.

Compartmentalization of Human Stem Cell-Derived Neurons within Pre-Assembled Plastic Microfluidic Chips

Use of microfluidic devices to compartmentalize cultured neurons has become a standard method in neuroscience. This protocol shows how to use a pre-assembled multi-compartment chip made in a cyclic olefin copolymer (COC) to compartmentalize neurons differentiated from human stem cells. The footprint of these COC chips are the same as a standard microscope slide and are equally compatible with high resolution microscopy. Neurons are differentiated from human neural stem cells (NSCs) into glutamatergic neurons within the chip and maintained for 5 weeks, allowing sufficient time for these neurons to develop synapses and dendritic spines. Further, we demonstrate multiple common experimental procedures using these multi-compartment chips, including viral labeling, establishing microenvironments, axotomy, and immunocytochemistry.

Inhibition of P53/miR-34a improves diabetic endothelial dysfunction via activation of SIRT1

Endothelial dysfunction contributes to diabetic macrovascular complications, resulting in high mortality. Recent findings demonstrate a pathogenic role of P53 in endothelial dysfunction, encouraging the investigation of the effect of P53 inhibition on diabetic endothelial dysfunction. Thus, high glucose (HG)‐treated endothelial cells (ECs) were subjected to pifithrin‐α (PFT‐α)—a specific inhibitor of P53, or P53‐small interfering RNA (siRNA), both of which attenuated the HG‐induced endothelial inflammation and oxidative stress. Moreover, inhibition of P53 by PFT‐α or P53‐siRNA prohibited P53 acetylation, decreased microRNA‐34a (miR‐34a) level, leading to a dramatic increase in sirtuin 1 (SIRT1) protein level. Interestingly, the miR‐34a inhibitor (miR‐34a‐I) and PFT‐α increased SIRT1 protein level and alleviated the HG‐induced endothelial inflammation and oxidative stress to a similar extent; however, these effects of PFT‐α were completely abrogated by the miR‐34a mimic. In addition, SIRT1 inhibition by EX‐527 or Sirt1‐siRNA completely abolished miR‐34a‐I's protection against HG‐induced endothelial inflammation and oxidative stress. Furthermore, in the aortas of streptozotocin‐induced diabetic mice, both PFT‐α and miR‐34a‐I rescued the inflammation, oxidative stress and endothelial dysfunction caused by hyperglycaemia. Hence, the present study has uncovered a P53/miR‐34a/SIRT1 pathway that leads to endothelial dysfunction, suggesting that P53/miR‐34a inhibition could be a viable strategy in the management of diabetic macrovascular diseases.

Verapamil Attenuated Prediabetic Neuropathy in High-Fat Diet-Fed Mice through Inhibiting TXNIP-Mediated Apoptosis and Inflammation

Diabetic neuropathy (DN) is a common and severe complication of diabetes mellitus. There is still a lack of an effective treatment to DN because of its complex pathogenesis. Thioredoxin-interacting protein (TXNIP), an endogenous inhibitor of thioredoxin, has been shown to be associated with diabetic retinopathy and nephropathy. Herein, we aim to investigate the role of TXNIP in prediabetic neuropathy and therapeutic potential of verapamil which has been shown to inhibit TXNIP expression. The effects of mediating TXNIP on prediabetic neuropathy and its exact mechanism were performed using high-fat diet- (HFD-) induced diabetic mice and palmitate-treated neurons. Our results showed that TXNIP upregulation is associated with prediabetic neuropathy in HFD-fed mice. TXNIP knockdown improved DN in HFD-induced prediabetic mice. Mechanistically, increased TXNIP in dorsal root ganglion is transferred into the cytoplasm and shuttled to the mitochondria. In cytoplasm, TXNIP binding to TRX1 results in the increased oxidative stress and inflammation. In mitochondria, TXNIP binding to TRX2 induced mitochondria dysfunction and apoptosis. TXNIP isolated from TRX2 then shuttles to the cytoplasm and binds to NLRP3, resulting in further increased TXNIP-NLRP3 complex, which induced the release of IL-1β and the development of inflammation. Thus, apoptosis and inflammation of dorsal root ganglion neuron eventually cause neural dysfunction. In addition, we also showed that verapamil, a known inhibitor of calcium channels, improved prediabetic neuropathy in the HFD-fed mice by inhibiting the upregulation of TXNIP. Our finding suggests that TXNIP might be a potential target for the treatment of neuropathy in prediabetic patients with dyslipidemia.

MiR-20a Plays a Key Regulatory Role in the Repair of Spinal Cord Dorsal Column Lesion via PDZ-RhoGEF/RhoA/GAP43 Axis in Rat

Spinal cord injury (SCI) causes sensory dysfunctions such as paresthesia, dysesthesia, and chronic neuropathic pain. MiR-20a facilitates the axonal outgrowth of the cortical neurons. However, the role of miR-20a in the axonal outgrowth of primary sensory neurons and spinal cord dorsal column lesion (SDCL) is yet unknown. Therefore, the role of miR-20a post-SDCL was investigated in rat. The NF-200 immunofluorescence staining was applied to observe whether axonal outgrowth of dorsal root ganglion (DRG) neurons could be altered by miR-20a or PDZ-RhoGEF modulation in vitro. The expression of miR-20a was quantized with RT-PCR. Western blotting analyzed the expression of PDZ-RhoGEF/RhoA/GAP43 axis after miR-20a or PDZ-RhoGEF was modulated. The spinal cord sensory conduction function was assessed by somatosensory-evoked potentials and tape removal test. The results demonstrated that the expression of miR-20a decreased in a time-dependent manner post-SDCL. The regulation of miR-20a modulated the axonal growth and the expression of PDZ-RhoGEF/RhoA/GAP43 axis in vitro. The in vivo regulation of miR-20a altered the expression of miR-20a-PDZ-RhoGEF/RhoA/GAP43 axis and promoted the recovery of ascending sensory function post-SDCL. The results indicated that miR-20a/PDZ-RhoGEF/RhoA/GAP43 axis is associated with the pathophysiological process of SDCL. Thus, targeting the miR-20a/PDZ-RhoGEF /RhoA/GAP43 axis served as a novel strategy in promoting the sensory function recovery post-SCI.

Exosomes derived from high-glucose-stimulated Schwann cells promote development of diabetic peripheral neuropathy

Schwann cells actively interact with axons of dorsal root ganglia (DRG) neurons. Exosomes mediate intercellular communication by transferring their biomaterials, including microRNAs (miRs) into recipient cells. We hypothesized that exosomes derived from Schwann cells stimulated by high glucose (HG) exosomes accelerate development of diabetic peripheral neuropathy and that exosomal cargo miRs contribute to this process. We found that HG exosomes contained high levels of miR-28, -31a, and -130a compared to exosomes derived from non-HG-stimulated Schwann cells. In vitro, treatment of distal axons with HG exosomes resulted in reduction of axonal growth, which was associated with elevation of miR-28, -31a, and -130a and reduction of their target proteins of DNA methyltransferase-3α, NUMB (an endocytic adaptor protein), synaptosome associated protein 25, and growth-associated protein-43 in axons. In vivo, administration of HG exosomes to sciatic nerves of diabetic db/db mice at 7 wk of age promoted occurrence of peripheral neuropathy characterized by impairment of nerve conduction velocity and induction of mechanic and thermal hypoesthesia, which was associated with substantial decreases in intraepidermal nerve fibers. Our findings demonstrate a functional role of exosomes derived from HG-stimulated Schwann cells in mediating development of diabetic peripheral neuropathy.-Jia, L., Chopp, M., Wang, L., Lu, X., Szalad, A., Zhang, Z. G. Exosomes derived from high-glucose-stimulated Schwann cells promote development of diabetic peripheral neuropathy.

Structure before function: myosin binding protein-C slow is a structural protein with regulatory properties

Myosin binding protein-C slow (sMyBP-C) comprises a family of accessory proteins in skeletal muscles that bind both myosin and actin filaments. Herein, we examined the role of sMyBP-C in adult skeletal muscles using in vivo gene transfer and clustered regularly interspaced short palindromic repeats technology to knock down all known sMyBP-C variants. Our findings, confirmed in two different skeletal muscles, demonstrated efficient knockdown (KD) of sMyBP-C (>70%) resulting in notably decreased levels of thick, but not thin, filament proteins ranging from ∼50% for slow and fast myosin to ∼20% for myomesin. Consistent with this, A bands were selectively distorted, and sarcomere length was significantly reduced. Contrary to earlier in vitro studies showing that addition of recombinant sMyBP-C slows down the formation of actomyosin crossbridges, our work demonstrates that KD of sMyBP-C in intact myofibers results in decreased contraction and relaxation kinetics under no-load conditions. Similarly, KD muscles develop markedly reduced twitch and tetanic force and contraction velocity. Taken together, our results show that sMyBP-C is essential for the regular organization and maintenance of myosin filaments into A bands and that its structural role precedes its ability to regulate actomyosin crossbridges.-Geist, J., Ward, C. W., Kontrogianni-Konstantopoulos, A. Structure before function: myosin binding protein-C slow is a structural protein with regulatory properties.