Ocular Nerve Growth Factor Administration Modulates Brain-derived Neurotrophic Factor Signaling in Prefrontal Cortex of Healthy and Diabetic Rats

Targeting BDNF with acupuncture: A novel integrated strategy for diabetes and depression comorbidity

Diabetes and depression are common comorbid conditions that impose a substantial health burden. Acupuncture may effectively improve symptoms in patients with diabetes and depression, but the underlying mechanism remains unclear. Brain-derived neurotrophic factor (BDNF) may play a vital role in the effects of acupuncture on diabetes and depression comorbidity. This review summarizes the potential role of BDNF in acupuncture for diabetes and depression comorbidity. BDNF appears to exert its effects via the BDNF-TrkB-ERK-CREB signaling pathway. BDNF levels are reduced in diabetes and depression, and acupuncture may increase BDNF expression, improving symptoms and glycemic control. High-quality research is needed to validate the efficacy of acupuncture for diabetes and depression comorbidity. Randomized controlled trials and mechanistic studies should investigate the BDNF pathway and other potential mechanisms. Improved understanding of the links between diabetes, depression and acupuncture may enable targeted and individualized patient care. Earlier diagnosis and management of diabetes and depression comorbidity should also be a priority.

Bell's palsy was associated with TRPV2 downregulation of Schwann cell by cold stress

OBJECTIVE

Epidemiological and clinical studies have shown that sharp changes in the ambient temperature are associated with the occurrence and development of Bell's palsy. However, the specific pathogenesis of peripheral facial paralysis remains nebulous. This study investigated the effect of cold stress on transient receptor potential cation channel subfamily V member 2 (TRPV2) secretion by Schwann cells and its role in Bell's palsy.

MATERIALS AND METHODS

Schwann cell morphology was observed using transmission electron microscopy (TEM). Cell proliferation, apoptosis and cell cycle were analysed using CCK8 and flow cytometry. ELISA, Reverse transcription-quantitative PCR, western blotting and immunocytochemical fluorescence staining were used to detect the effects of cold stress on TRPV2, neural cell adhesion molecule (NCAM) and nerve growth factor (NGF) expression in Schwann cells.

RESULTS

Cold stress resulted in a widening of the intercellular space, and the particles on the membrane showed different degrees of loss. Cold stress may cause Schwann cells to enter a cold dormant state. ELISA, RT-qPCR, western blotting and immunocytochemical fluorescences staining indicated that cold stress inhibited the expression of TRPV2, NCAM, and NGF.

CONCLUSIONS

Drastic temperature difference between cold and heat can downregulate TRPV2 and the secretome of Schwann cells. The imbalance of Schwann cell homeostasis under such stress may contribute to nerve signalling dysfunction leading to the development of facial paralysis.

Psycho-Cognitive Profile and NGF and BDNF Levels in Tears and Serum: A Pilot Study in Patients with Graves' Disease

Nerve Growth Factor (NGF) and Brain derived Neurotrophic Factor (BDNF) mature/precursor imbalance in tears and serum is suggested as a risk factor and symptomatology aggravation in ophthalmology and neuropsychiatric disturbances. Cognitive and mood alterations are reported by patients with Graves' Orbitopathy (GO), indicating neurotrophin alterations might be involved. To address this question, the expression levels of NGF and BDNF and their precursors in serum and tears of GO patients were analyzed and correlated with the ophthalmological and psycho-cognitive symptoms. Hamilton Rating Scale for Anxiety (HAM-A) and Depression (HAM-D), Temperament and Character Inventory (TCI), and Cambridge Neuropsychological Test Automated Battery (CANTAB) test were used as a score. NGF and BDNF levels were measured using ELISA and Western Blot and statistically analyzed for psychiatric/ocular variable trend association. GO patients show memorization time and level of distraction increase, together with high irritability and impulsiveness. HAM-A and CANTAB variables association, and some TCI dimensions are also found. NGF and BDNF expression correlates with ophthalmological symptoms only in tears, while mature/precursor NGF and BDNF correlate with the specific psycho-cognitive variables both in tears and serum. Our study is the first to show that changes in NGF and BDNF processing in tears and serum might profile ocular and cognitive alterations in patients.

Long-term treatment with roflumilast improves learning of fear extinction memory and anxiety-like response in a type-1 diabetes mellitus animal model

Diabetic encephalopathy is related to serious damage to the Central Nervous System leading to several disturbances in memory processing and emotions. It is known that the cyclic adenosine 3',5'-monophosphate (cAMP) responsive element-binding protein (CREB) pathway participates in neuronal plasticity and prevention of neuroinflammation, as well as the mediation of learning/memory processes and emotions in brain areas such as the hippocampus (HIP) and prefrontal cortex (PFC). We aimed to investigate the effect of acute (one injection) and long-term treatment (21 days) with roflumilast (ROF; i.p.; 0, 0.01, 0.03, 0.1 mg/kg), a drug able to inhibit the enzyme phosphodiesterase-4 (PDE-4) responsible for cAMP hydrolysis, on parameters related to the acquisition of fear extinction memory and anxiety-like responses in animals with type-1 diabetes mellitus (T1DM) induced through one injection of streptozotocin (60 mg/kg; ip; STZ animals). When we performed acute treatment, no difference was observed between all the groups when resubmitted to the same context paired with an aversive stimulus (footshock) or to a neutral context. In contrast, long-term treatment was able to improve learning of extinction fear memory and discriminating between a conditioned and neutral context. Moreover, this treatment decreased the pronounced anxiety-like response of STZ animals. In addition, there was an increase in the product of the CREB signaling pathway, the pro brain-derived neurotrophic factor, in the HIP and PFC of these animals. The treatment did not impair glycemic control, whereas it decreased the animal's blood glucose levels. To conclude, these findings suggest that ROF treatment repositioning has potential for future translational investigations involving diabetic patients considering its beneficial effects on emotional processes related to fear memory and anxiety, in addition to improvement of glycemic control.

A randomized clinical trial to test efficacy of chamomile and saffron for neuroprotective and anti-inflammatory responses in depressive patients

Depression is one of the common psychiatric problems in growing world population caused by long-term stressful events that may trigger the down regulation of neurogenesis. The pathogenesis of depression initially relies on serotonin deficiency which is associated with depressive feelings. Tryptophan (TRP) depletion participate crucial role in inducing depressive symptoms. Long-term reduction of 5-HT may disseminate to high sensitivity of MDD and alters the level of BDNF. Some studies have also revealed the strong association between excessive neuroinflammation and BDNF levels, due the release of pro-inflammatory cytokines. The treatment approach through FDA approved medicine has their own merits and drawbacks. Therefore, herbal alternatives have recently garnered attention for their effectiveness against depression. However, evidence-based synergic effects of antidepressant with different herbal agents are limited. The purpose of this study was to assess the synergistic effects of two well-known herbs, chamomile and saffron, as an adjuvant therapy in patients with mild to moderate depression. The present study was study randomized, open, blinded trial and comprised of 120 participants randomly allocated to control (n = 60) and test (n = 60). After consent, the patient health questionnaire- 9 (PHQ-9) was filled to obtain depression scores. The test participants were received herbal tea sachets twice a day for one month (20 mg Chamomile and 1 mg Saffron/sachet) along with routine medicines, while control participants were received only allopathic medications. Blood samples were taken before and after the treatment. The depressive symptoms improved significantly with both treatments. The effect of herbs enhanced the efficacy of medications and significantly improved PHQ-9 scale and BDNF while reduced the inflammatory markers (CRP) and TRP level in plasma thereby increased the availability of TRP in brain. It has been concluded that the herbal adjuvant therapy produced long term improvement against depression and enhanced the efficacy of allopathic treatment.

NGF Modulates Cholesterol Metabolism and Stimulates ApoE Secretion in Glial Cells Conferring Neuroprotection against Oxidative Stress

Cholesterol plays a crucial role in the brain, where its metabolism is particularly regulated by astrocytic activity. Indeed, adult neurons suppress their own cholesterol biosynthesis and import this sterol through ApoE-rich particles secreted from astrocytes. Recent evidence suggests that nerve growth factor (NGF) may exert neurotrophic activity by influencing cell metabolism. Nevertheless, the effect of NGF on glial cholesterol homeostasis has still not been elucidated. Thus, the aim of this project is to assess whether NGF could influence cholesterol metabolism in glial cells. To reach this objective, the U373 astrocyte-derived cell line was used as an experimental model. Immunoblot and ELISA analysis showed that proteins and enzymes belonging to the cholesterol metabolism network were increased upon NGF treatment in glial cells. Furthermore, NGF significantly increased ApoE secretion and the amount of extracellular cholesterol in the culture medium. Co-culture and U373-conditioned medium experiments demonstrated that NGF treatment efficiently counteracted rotenone-mediated cytotoxicity in N1E-115 neuronal cells. Conversely, neuroprotection mediated by NGF treatment was suppressed when N1E-115 were co-cultured with ApoE-silenced U373 cells. Taken together, these data suggest that NGF controls cholesterol homeostasis in glial cells. More importantly, NGF exerts neuroprotection against oxidative stress, which is likely associated with the induction of glial ApoE secretion.

Serum BDNF and suicidal ideation in drug-naïve and drug-treated MDD patients: a case–control study

Background

Disturbances in structural and synaptic plasticity have been linked to depression and suicidal ideation. One of the major neurotrophic factors, the brain-derived neurotrophic factor (BDNF), is involved in the maintenance and survival of neurons and synaptic plasticity. This case–control study assesses the serum BDNF and suicidal ideation among drug-naïve and drug-treated MDD patients attending university hospitals and comparing them to healthy control. A simple random sample of 57 MDD patients and 57 age- and sex-comparable controls were enrolled. The researchers conducted a semi-structured interview to collect the demographic characteristics and disease history. Structured Clinical Interview for DSM-5 (SCID-5), Hamilton Depression Rating Scale (HDRS), and Beck Scale for Suicidal Ideation (BSS) were applied to the participants. Blood samples were collected to measure plasma BDNF level.

Results

The MDD group had lower BDNF than the control group. Within the MDD group, drug-naïve patients had significantly lower BDNF than drug-treated patients. Female patients had lower BDNF than male patients. Positive family history of MDD was associated with low BDNF. Severe and moderate cases had lower BDNF than mild cases. High BSS (≥24) was associated with low BDNF. A statistically significant positive correlation was found between BDNF and age, disease duration, duration of the current episode, and the number of previous episodes.

On the other hand, a statistically significant negative correlation was found between BDNF and age of MDD onset, HDRS, and BSS. A regression model was highly statistically significant in the prediction of HDRS. BDNF and disease duration were negatively correlated with HDRS. On the other hand, depression treatment status was not significantly associated with the HDRS prediction model.

Conclusion

Our findings extend the neurotrophic concept of depression by identifying the decreased BDNF levels as a peripheral biomarker of MDD. Our assessment of depression and suicidal ideation (SI) and their relationship to decreased BDNF levels shed light on the etiopathology of MDD and its related suicidality. They should be more studied to understand better the mechanisms by which they develop. To further explore the effect of BDNF in suicide, larger study sizes and a range of psychiatric diagnoses associated with suicide attempts are required.

NGF Eye Administration Recovers the TrkB and Glutamate/GABA Marker Deficit in the Adult Visual Cortex Following Optic Nerve Crush

Eye-drop recombinant human nerve growth factor (ed-rhNGF) has proved to recover the retina and optic nerve damage in animal models, including the unilateral optic nerve crush (ONC), and to improve visual acuity in humans. These data, associated with evidence that ed-rhNGF stimulates the brain derived neurotrophic factor (BDNF) in retina and cortex, suggests that NGF might exert retino-fugal effects by affecting BDNF and its receptor TrkB. To address these questions, their expression and relationship with the GABAergic and glutamatergic transmission markers, GAD65 and GAD67, vesicular inhibitory amino acid transporter (VGAT), and vesicular glutamate transporters 1 and 2 (VGLUT-1 and VGLUT-2) were investigated in adult ONC rats contralateral and ipsilateral visual cortex (VCx). Ed-rhNGF recovers the ONC-induced alteration of GABAergic and glutamatergic markers in contralateral VCx, induces an upregulation of TrkB, which is positively correlated with BDNF precursor (proBDNF) decrease in both VCx sides, and strongly enhances TrkB+ cell soma and neuronal endings surrounded by GAD65 immuno-reactive afferents. These findings contribute to enlarging the knowledge on the mechanism of actions and cellular targets of exogenously administrated NGF, and suggest that ed-rhNGF might act by potentiating the activity-dependent TrkB expression in GAD+ cells in VCx following retina damage and/or ONC.

Nerve Growth Factor Protects Retinal Ganglion Cells Related to Inhibiting Endoplasmic Reticulum Stress by Inhibiting IRE1-JNK-CHOP Signaling Pathway

BACKGROUND

Under various physiological conditions, endoplasmic reticulum stress can induce apoptotic cell death, leading to brain and retinal neuronal cell death, but the relations of ER stress-induced apoptosis and the nerve growth factor's therapeutic effect in Glaucoma optic neuropathy still unclear.

METHODS

An endoplasmic reticulum stress model was established in ganglion cells using TG, the endoplasmic reticulum stress inducer. MTT assay and flow cytometry were used to detect the protective effect of NGF on retinal ganglion cells. Western blot was used to detect apoptosis-related proteins Bcl-2, Bad and endoplasmic reticulum stress-related proteins GRP78, IRE1, JNK and CHOP.

RESULTS

MTT assay and flow cytometry showed NGF can protect the apoptosis of ganglion cells. Western blot analysis showed the level of pro-apoptotic protein Bad was decreased and anti-apoptotic protein Bcl-2 was increased after NGF treatment. Endoplasmic reticulum stress-induced proteins GRP78, IRE1, JNK and CHOP are counter- acted by NGF.

CONCLUSION

NGF protects retinal ganglion cells related to inhibiting endoplasmic reticulum stress by inhibiting IRE1-JNK-CHOP signaling pathway.

Blood Brain-Derived Neurotrophic Factor (BDNF) and Major Depression: Do We Have a Translational Perspective?

Major depressive disorder (MDD) affects millions of people worldwide and is a leading cause of disability. Several theories have been proposed to explain its pathological mechanisms, and the “neurotrophin hypothesis of depression” involves one of the most relevant pathways. Brain-derived neurotrophic factor (BDNF) is an important neurotrophin, and it has been extensively investigated in both experimental models and clinical studies of MDD. Robust empirical findings have indicated an association between increased BDNF gene expression and peripheral concentration with improved neuronal plasticity and neurogenesis. Additionally, several studies have indicated the blunt expression of BDNF in carriers of the Val66Met gene polymorphism and lower blood BDNF (serum or plasma) levels in depressed individuals. Clinical trials have yielded mixed results with different treatment options, peripheral blood BDNF measurement techniques, and time of observation. Previous meta-analyses of MDD treatment have indicated that antidepressants and electroconvulsive therapy showed higher levels of blood BDNF after treatment but not with physical exercise, psychotherapy, or direct current stimulation. Moreover, the rapid-acting antidepressant ketamine has presented an early increase in blood BDNF concentration. Although evidence has pointed to increased levels of BDNF after antidepressant therapy, several factors, such as heterogeneous results, low sample size, publication bias, and different BDNF measurements (serum or plasma), pose a challenge in the interpretation of the relation between peripheral blood BDNF and MDD. These potential gaps in the literature have not been properly addressed in previous narrative reviews. In this review, current evidence regarding BDNF function, genetics and epigenetics, expression, and results from clinical trials is summarized, putting the literature into a translational perspective on MDD. In general, blood BDNF cannot be recommended for use as a biomarker in clinical practice. Moreover, future studies should expand the evidence with larger samples, use the serum or serum: whole blood concentration of BDNF as a more accurate measure of peripheral BDNF, and compare its change upon different treatment modalities of MDD.

Nerve Growth Factor in Alcohol Use Disorders

The nerve growth factor (NGF) belongs to the family of neurotrophic factors. Initially discovered as a signaling molecule involved in the survival, protection, differentiation, and proliferation of sympathetic and peripheral sensory neurons, it also participates in the regulation of the immune system and endocrine system. NGF biological activity is due to the binding of two classes of receptors: the tropomyosin-related kinase A (TrkA) and the low-affinity NGF pan-neurotrophin receptor p75. Alcohol Use Disorders (AUD) are one of the most frequent mental disorders in developed countries, characterized by heavy drinking, despite the negative effects of alcohol on brain development and cognitive functions that cause individual’s work, medical, legal, educational, and social life problems. In addition, alcohol consumption during pregnancy disrupts the development of the fetal brain causing a wide range of neurobehavioral outcomes collectively known as fetal alcohol spectrum disorders (FASD). The rationale of this review is to describe crucial findings on the role of NGF in humans and animals, when exposed to prenatal, chronic alcohol consumption, and on binge drinking.

Vagus nerve stimulation and Neurotrophins: a biological psychiatric perspective

Since 2004, vagus nerve stimulation (VNS) has been used in treatment-resistant or treatment-intolerant depressive episodes. Today, VNS is suggested as possible therapy for a larger spectrum of psychiatric disorders, including schizophrenia, obsessive compulsive disorders, and panic disorders. Despite a large body of literature supports the application of VNS in patients' treatment, the exact mechanism of action of VNS remains not fully understood. In the present study, the major knowledges on the brain areas and neuronal pathways regulating neuroimmune and autonomic response subserving VNS effects are reviewed. Furthermore, the involvement of the neurotrophins (NTs) Nerve Growth Factor (NGF) and Brain Derived Neurotrophic Factor (BDNF) in vagus nerve (VN) physiology and stimulation is revised. The data on brain NGF/BDNF synthesis and in turn on the activity-dependent plasticity, connectivity rearrangement and neurogenesis, are presented and discussed as potential biomarkers for optimizing stimulatory parameters for VNS. A vagus nerve-neurotrophin interaction model in the brain is finally proposed as a working hypothesis for future studies addressed to understand pathophysiology of psychiatric disturbance.

The role of neurotrophins in psychopathology and cardiovascular diseases: psychosomatic connections

Cardiovascular (CV) diseases and mood disorders are common public health problems worldwide. Their connections are widely studied, and the role of neurotrophins (NTs) is already supposed in both conditions. However, data in the literature of clinical aspects are sometimes controversial and no reviews are available describing possible associations between CV risk and mood disorders based on NTs. The mostly studied NT is brain-derived neurotrophic factor (BDNF). Decreased level of BDNF is observed in depression and its connection to hypertension has also been demonstrated with affecting the arterial baroreceptors, renin–angiotensin system and endothelial nitric oxide synthase. BDNF was also found to be the predictor of CV outcome in different patient populations. Other types of human NT-s, such as nerve growth factor, neurotrophin 3 and neurotrophin 4 also seem to have both psychopathological and CV connections. Our aim was to overview the present knowledge in this area, demonstrating a new aspect of the associations between mood disorders and CV diseases through the mediation of NTs. These findings might enlighten new psychosomatic connections and suggest new therapeutic targets that are beneficial both in respect of mood disorders and CV pathology.

Ocular Nerve Growth Factor (NGF) and NGF Eye Drop Application as Paradigms to Investigate NGF Neuroprotective and Reparative Actions

The eye is a central nervous system structure that is uniquely accessible to local treatment. Through the ocular surface, it is possible to access the retina, optic nerve, and brain. Animal models of retina degeneration or optic nerve crush could thus serve as tools to investigate whether and how factors, which are anterogradely or retrogradely transported through the optic nerve, might contribute to activate neuroprotection and eventually regeneration. Among these factors, nerve growth factor (NGF) plays a crucial role during development of the visual system, as well as during the entire life span, and in pathological conditions. The ability of NGF to exert survival and trophic actions on the retina and brain cells when applied intraocularly and topically as eye drops is critically reviewed here, together with the effects of ocular neurotrophins on neuronal pathways influencing body rhythm, cognitions, and behavioral functions. The latest data from animal models and humans are presented, and the mechanism of action of ocularly administered NGF is discussed. NGF eye drops are proposed as an experimental strategy to investigate the role and cellular targets of neurotrophins in the mechanism(s) underlying neurodegeneration/regeneration and their involvement in the regulation of neurological and behavioral dysfunctions.