Activation of the NGF/TrkA signaling pathway attenuates diabetic erectile dysfunction

Mechanisms by which spinal cord stimulation intervenes in atrial fibrillation: The involvement of the endothelin-1 and nerve growth factor/p75NTR pathways

Can the spinal cord stimulation (SCS) regulate the autonomic nerves through the endothelin-1 (ET-1) and nerve growth factor (NGF)/p75NTR pathways and thus inhibit the occurrence of atrial fibrillation (AF)? In our research, 16 beagles were randomly divided into a rapid atrial pacing (RAP) group (n = 8) and a RAP + SCS group (n = 8), and the effective refractory period (ERP), ERP dispersion, AF induction rate, and AF vulnerability window (WOV) at baseline, 6 h of RAP, 6 h of RAP + SCS were measured. The atrial tissue was then taken for immunohistochemical analysis to determine the localization of ET-1, NGF, p75NTR, NF-kB p65, and other genes. Our results showed that SCS attenuated the shortening of ERP in all parts caused by RAP, and after 6 h of SCS, the probability of AF in dogs was reduced compared with that in the RAP group. Moreover, the expression of ET-1, NGF, and p75NTR in the atrial tissues of dogs in the RAP + SCS group was significantly increased, but the expression of NF-kB p65 was reduced. In conclusion, SCS promotes the positive remodeling of cardiac autonomic nerves by weakening NFκB p65-dependent pathways to interfere with the ET-1 and NGF/p75NTR pathways to resist the original negative remodeling and inhibit the occurrence of AF.

Functional recovery of injured cavernous nerves achieved through endogenous nerve growth factor-containing bioactive fibrous membrane

Radical prostatectomy is a highly successful treatment for prostate cancer, among the most prevalent manifestations of the illness. Damage of the cavernous nerve (CN) during prostatectomy is the main cause of postoperative erectile dysfunction (ED). In this study, the capability of a personalized bioactive fibrous membrane to regenerate injured CN was investigated. The fibrous membrane bioactivity is conferred by the selectively bound nerve growth factor (NGF) present in the rat urine. In a rat model of bilateral CN crush, the implanted bioactive fibrous membrane induces CN regeneration and restoration of erectile function, showing a significantly increased number of smooth muscle cells and content of endothelial and neuronal nitric oxide synthases (eNOS; nNOS). In addition, the bioactive fibrous membrane promotes nerve regeneration by increasing the number of myelinated axons and nNOS-positive cells, therefore reversing the CN fibrosis found in untreated rats or rats treated with a bare fibrous membrane. Therefore, this personalized regenerative strategy could overcome the recognized drawbacks of currently available treatments for CN injuries. It may constitute an effective treatment for prostate cancer patients suffering from ED after being subject to radical prostatectomy. STATEMENT OF SIGNIFICANCE: The present work introduces a unique strategy to address post-surgical ED resulting from CN injury during pelvic surgery (e.g., radical prostatectomy, radical cystoprostatectomy, abdominoperineal resection). It comprises a bioactive and cell-free fibrous implant, customized to enhance CN recovery. Pre-clinical results in a rat model of bilateral CN crush demonstrated that the bioactive fibrous implant can effectively heal injured CN, and restore penile structure and function. This implant selectively binds NGF from patient fluids (i.e. urine) due to its functionalized surface and high surface area. Moreover, its local implantation reduces adverse side effects. This tailored regenerative approach has the potential to revolutionize the treatment of ED in prostate cancer patients following radical prostatectomy, overcoming current treatment limitations.

Nerve Growth Factor Promotes Retinal Neurovascular Unit Repair: A Review

Purpose: The purpose of this paper is to investigate how the imbalance of neurogenic factor (NGF) and its precursor (pro-NGF) mediates structural and functional impairment of retinal neurovascular unit (RNVU) that plays a role in retinal degenerative diseases.Methods: A literature search of electronic databases was performed.Results: The pro-apoptotic effect of pro-NGF and the pro-growth effect of NGF are essential for the pathological and physiological activities of RNVU. Studies show that NGF-based treatment of retinal degenerative diseases, including glaucoma, age-related macular degeneration, retinitis pigmentosa, and diabetic retinopathy, has achieved remarkable efficacy.Conclusions: RNVU plays a complex and multifaceted role in retinal degenerative diseases. The exploration of the differential signaling expression of proNGF-NGF homeostasis under physiological and pathological conditions, and the corresponding pathological processes induced by its regulation, has prompted us to focus on earlier retinal neuroprotective therapeutic strategies to prevent retinal degenerative diseases.

The Occurrence of Valvular Atrial Fibrillation: Involvement of NGF/TrKA Signaling Pathway

OBJECTIVE

Nerve growth factor (NGF) and tropomyosin kinase receptors A (TrKA) exert a crucial effect on the regulation of autonomic nervous system which contributes to the progress of atrial fibrillation (AF). Valvular heart disease (VHD) patients are more easily to induce the AF. We investigated whether NGF/TrKA could impact the occurrence of AF in VHD patients.

MATERIALS AND METHODS

Atrial tissues were resected from 30 VHD patients with chronic AF (n = 15, AF >6 months) or sinus rhythm (SR, n = 15). The expression of NGF, TrKA, protein kinase B (PKB/Akt), beta-isoforms of glycogen synthase kinase-3 (GSK3β), Serine473 phosphorylation of Akt (p-Ser473 Akt), Serine9 phosphorylation of GSK-3β (p-Ser9 GSK3β) in right atrial tissues and peripheral blood lymphocyte were quantified by Western blot. The localization of those genes expression was measured by immunohistochemistry. Double sandwich enzyme-linked immunosorbent assay was used to observe the trace changes of NGF-β in peripheral plasma.

RESULTS

Our results revealed that the NGF expression was markedly elevated in the tissue of right atrial appendage and peripheral blood lymphocytes from AF patients compared with the SR patients. But, the expression of TrKA, GSK3β, p-Akt and p-GSK3β were decreased. There was no difference about the expression of Akt from the AF patients and the SR patients. The NGF-β level in peripheral blood plasma of patients with AF and SR was not statistical difference.

CONCLUSION

Thus, we thought that NGF/TrKA signaling pathway may be involved in the AF in the patients with VHD, inactivation of GSK3β could increase the incidence of AF, but not relevant to phosphorylation.

Involvement of neurotrophic signaling in doxorubicin-induced cardiotoxicity

Dose dependent cardiotoxicity is the primary side effect of doxorubicin (DOX), but the underlying molecular mechanisms remain unclear. An increasing amount of evidence has demonstrated that neurotrophic signaling plays a pivotal role in both neurons and the heart, but the biological association between neurotrophic signaling and DOX-induced cardiotoxicity remains unknown. The present study determined the level of neurotrophins and their receptors in the heart of rats following DOX administration. DOX was administered 7 times at a dose of 2.5 mg/kg once every 2 days via intraperitoneal injection. The present study revealed that cardiac injury parameters, such as creatine kinase (CK), creatine kinase-myocardial bound, lactate dehydrogenase, troponin T and aspartate transaminase in serum were significantly increased in the DOX group. Both the gene and protein expression of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the heart were markedly decreased following DOX treatment. Notably, the protein level of BDNF in the serum was inhibited in DOX-treated rats, whereas DOX induced a significant increase in the protein level of NGF in the serum. DOX induced a significant decrease in the level of tropomyosin-associated kinase A (TrkA) and the ratio of pTrkA/TrkA and pTrkB/TrkB. Furthermore, the administration of DOX suppressed downstream protein kinase B and extracellular signal regulated kinase phosphorylation. The present study first demonstrated that BDNF/TrkB signaling and NGF/TrkA signaling were altered by DOX, which indicated that neurotrophic signaling was involved in DOX-induced cardiotoxicity.

MicroRNA-141 binds to the nerve growth factor receptor associated protein 1 gene and restores the erectile function of diabetic rats through down-regulating the nerve growth factor/neurotrophin receptor p75 (NGF/p75NTR) signaling

BACKGROUND

Erectile dysfunction (ED) is one of the major complications in diabetes mellitus (DM). We have previously reported that the nerve growth factor (NGF)/tyrosine kinase receptor (TrkA) signaling is actively involved in DM-induced ED (DMED). Here, we investigate the effect of micro-RNA-141 (miR-141) on the NGF/p75 neurotrophin receptor (p75NTR) signaling and erectile function of diabetic rats.

METHODS

Sprague-Dawlay (SD) rats were used to establish a DMED model. The dual-luciferase reporter gene assay was first performed to identify the nerve growth factor receptor-associated protein 1 (NGFRAP1) gene as the target gene of miR-141. The regulatory mechanisms underlying miR-141 governing NGFRAP1 in vivo were then validated by modulating the expressions of miR-141 and knocking down NGFRAP1.

RESULTS

The expressions of miR-141 were decreased while the expressions of NGFRAP1, NGF, and p75NTR were increased in DMED. miR-141 and downregulation of NGFRAP1, respectively, increased the density of corpus cavernosum smooth muscle and the ratio of intracavernosal pressure (ICP)/mean arterial blood pressure (MAP) and promoted the expression of α-actin and desmin as well. miR-141 also upregulated the expressions of NGFRAP1 in DMED, and knockdown of NGFRAP1 inhibited the productions of NGF and p75NTR. Furthermore, miR-141 suppressed the NGF/p75NTR signaling via binding to NGFRAP1.

CONCLUSIONS

NGF/p75NTR signaling actively participates in the pathogenesis of DMED. miR-141 binds to NGFRAP1 and restores the erectile function of diabetic rats via downregulation of NGF/p75NTR signaling.