Protective effects of Ginkgo biloba extract EGb 761 against noise trauma-induced hearing loss and tinnitus development

Unveiling the Role of Oxidative Stress in Cochlear Hair Cell Death: Prospective Phytochemical Therapeutics against Sensorineural Hearing Loss

Hearing loss represents a multifaceted and pervasive challenge that deeply impacts various aspects of an individual's life, spanning psychological, emotional, social, and economic realms. Understanding the molecular underpinnings that orchestrate hearing loss remains paramount in the quest for effective therapeutic strategies. This review aims to expound upon the physiological, biochemical, and molecular aspects of hearing loss, with a specific focus on its correlation with diabetes. Within this context, phytochemicals have surfaced as prospective contenders in the pursuit of potential adjuvant therapies. These compounds exhibit noteworthy antioxidant and anti-inflammatory properties, which hold the potential to counteract the detrimental effects induced by oxidative stress and inflammation-prominent contributors to hearing impairment. Furthermore, this review offers an up-to-date exploration of the diverse molecular pathways modulated by these compounds. However, the dynamic landscape of their efficacy warrants recognition as an ongoing investigative topic, inherently contingent upon specific experimental models. Ultimately, to ascertain the genuine potential of phytochemicals as agents in hearing loss treatment, a comprehensive grasp of the molecular mechanisms at play, coupled with rigorous clinical investigations, stands as an imperative quest.

Otoprotective Effects of Quercetin Against Oxidative Damage in the Rat's Cochlea Induced by Noise and Silver Nanoparticles

The aim of this study was to investigate the otoprotective effects of Quercetin (Que) against both noise-induced hearing loss (NIHL) and the ototoxicity of silver nanoparticles (SNPs) in rats. Forty-two male Wistar rats were divided into seven groups (n = 6): control, SNPs, Que (100 mg/kg) plus SNPs (100 mg/kg), noise (104 dB), Que plus noise, noise plus SNPs, and noise plus Que plus SNPs. In the weight change results, there was no significant difference between the groups exposed to noise plus SNPs and SNPs compared to the control group. However, animals had significant changes in DPOAE amplitude at 1 and 3 days post-exposure when compared to baseline. Additionally, the DPOAE value of rats administered with Que plus SNPs was higher than in all other groups. Que also decreased the levels of TACT, MDA, IL-6, TNF-α, and NOX3 in the groups exposed to noise and SNPs and increased the SOD level and expression of myosin heavy chain VII (MYH7) and β-tubulin III (TUBB3) proteins. Furthermore, Que decreased structural changes in the animals' cochlea. Our findings indicate that pretreatment with Que efficiently counteracted the adverse effects of noise and SNPs on inner hair cell, outer hair cell, and nerve cells, which are responsible for high-frequency perception.

Age-related hearing loss and its potential drug candidates: a systematic review

BACKGROUND

Age-related hearing loss (ARHL) is one of the main illnesses afflicting the aged population and has a significant negative impact on society, economy, and health. However, there is presently no appropriate therapeutic treatment of ARHL due to the absence of comprehensive trials.

OBJECTIVES

The goal of this review is to systematically evaluate and analyze recent statistics on the pathologic classifications, risk factors, treatment strategies, and drug candidates of ARHL, including that from traditional Chinese medicine (TCM), to provide potential new approaches for preventing and treating ARHL.

METHODS

Literature related to ARHL was conducted in databases such as PubMed, WOS, China National Knowledge Infrastructure (CNKI), and Wanfang from the establishment of the database to Jan, 2023. The pathology, causal factor, pathophysiological mechanism, treatment strategy, and the drug candidate of ARHL were extracted and pooled for synthesis.

RESULTS

Many hypotheses about the etiology of ARHL are based on genetic and environmental elements. Most of the current research on the pathology of ARHL focuses on oxidative damage, mitochondrial dysfunction, inflammation, cochlear blood flow, ion homeostasis, etc. In TCM, herbs belonging to the kidney, lung, and liver meridians exhibit good hearing protection. Seven herbs belonging to the kidney meridian, 9 belonging to the lung meridian, and 4 belonging to the liver meridian were ultimately retrieved in this review, such as Polygonum multiflorum Thunb., Panax ginseng C.A. Mey, and Pueraria lobata (Willd.) Ohwi. Their active compounds, 2,3,4',5-Tetrahydroxystilbene-2-O-D-glucoside, ginsenoside Rb1, and puerarin, may act as the molecular substance for their anti-ARHL efficacy, and show anti-oxidative, neuroprotective, anti-inflammatory, anti-apoptotic, or mitochondrial protective effects.

CONCLUSION

Anti-oxidants, modulators of mitochondrial function, anti-inflammation agents, vasodilators, K+ channel openers, Ca2+ channel blockers, JNK inhibitors, and nerve growth factors/neurotrophic factors all contribute to hearing protection, and herbs are an important source of potential anti-ARHL drugs.

Combination Therapy of Choline Alfoscerate With Ginkgo biloba Monotherapy in Age-Related Hearing Loss: Effects and Outcomes

BACKGROUND AND OBJECTIVES

Ginkgo biloba and choline alfoscerate are used as adjuvant treatment for presbycusis, but studies on how the monotherapy differs from the combination therapy are lacking. Therefore, this study aimed to compare the audiologic outcomes between Ginkgo biloba monotherapy and Ginkgo biloba and choline alfoscerate combination therapy. Subjects and.

METHODS

The study groups are divided into three: negative control, monotherapy, and combination therapy groups. All groups' pure tone audiometry was measured by dividing the study period into Initial, 3-6, 6-9, 9-12, 12-15 months, and checked whether differences between groups were present.

RESULTS

The combination therapy showed less gradient gap than the monotherapy, indicating less hearing loss rate than the monotherapy. Based on the Kaplan-Meier curve, the combination therapy showed better results in terms of survival time of hearing.

CONCLUSIONS

As a pharmacological treatment for presbycusis, combination therapy shows better results than monotherapy.

Cardiovascular Activity of Ginkgo biloba-An Insight from Healthy Subjects

Ginkgo biloba is the oldest living tree species in the world. Despite less than encouraging clinical results, extracts from its leaves are among the most used herbal preparations in the prevention and treatment of cardiovascular diseases. Most data on the efficacy of Ginkgo biloba on cardiovascular disease is from clinical studies, with few results from healthy subjects. This paper aims to provide a comprehensive review of the mechanisms underlying the known beneficial cardiovascular activities of Ginkgo biloba. It displays myocardial suppressant and vasorelaxant activities ex vivo, potentiating endothelial-dependent and -independent pathways. It improves perfusion in different vascular beds, namely ocular, cochlear, cutaneous, cerebral, and coronary. Although scarce, evidence suggests that Ginkgo biloba displays a heterogeneous effect on tissue perfusion which is dependent on the individual elimination pathways. It displays an acceptable safety profile, with most reported adverse reactions constituting rare occurrences. Collectively, Ginkgo biloba positively impacts cardiovascular physiology, improving hemodynamics and organ perfusion. In the future, better controlled clinical studies should be performed in order to identify the target populations who may benefit the most from pharmacotherapeutic interventions involving Ginkgo biloba.

Ginkgo biloba for tinnitus

BACKGROUND

Tinnitus is a symptom defined as the perception of sound in the absence of an external source. In England alone there are an estimated ¾ million general practice consultations every year where the primary complaint is tinnitus, equating to a major burden on healthcare services. Clinical management strategies include education and advice, relaxation therapy, tinnitus retraining therapy (TRT), cognitive behavioural therapy (CBT), sound enrichment using ear-level sound generators or hearing aids, and drug therapies to manage co-morbid symptoms such as insomnia, anxiety or depression.  OBJECTIVES: To assess the effects of Ginkgo biloba for tinnitus in adults and children.

SEARCH METHODS

The Cochrane ENT Information Specialist searched the Cochrane ENT Register; CENTRAL (2022, Issue 6); Ovid MEDLINE; Ovid Embase; CINAHL; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the search was 7 June 2022.

SELECTION CRITERIA

Randomised controlled trials (RCTs) recruiting adults and children with acute or chronic subjective tinnitus. We included studies where the intervention involved Ginkgo biloba and this was compared to placebo, no intervention, or education and information. Concurrent use of other medication or other treatment was acceptable if used equally in each group. Where an additional intervention was used equally in both groups, we analysed this as a separate comparison. The review included all courses of Ginkgo biloba, regardless of dose regimens or formulations, and for any duration of treatment.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were tinnitus symptom severity measured as a global score on a multi-item tinnitus questionnaire and serious adverse effects (bleeding, seizures). Our secondary outcomes were tinnitus loudness (change in subjective perception), tinnitus intrusiveness, generalised depression, generalised anxiety, health-related quality of life and other adverse effects (gastrointestinal upset, headache, allergic reaction). We used GRADE to assess the certainty of the evidence for each outcome.

MAIN RESULTS

This review included 12 studies (with a total of  1915 participants). Eleven studies compared the effects of Ginkgo biloba with placebo and one study compared the effects of Ginkgo biloba with hearing aids to hearing aids alone. All included studies were parallel-group RCTs. In general, risk of bias was high or unclear due to selection bias and poor reporting of allocation concealment and blinding of participants, personnel and outcome assessments. Due to heterogeneity in the outcomes measured and measurement methods used, only limited data pooling was possible.  Ginkgo biloba versus placebo When we pooled data from two studies for the primary outcome tinnitus symptom severity, we found that Ginkgo biloba may have little to no effect (Tinnitus Handicap Inventory scores) at three to six months compared to placebo, but the evidence is very uncertain (mean difference (MD) -1.35 (scale 0 to 100), 95% confidence interval (CI) -8.26 to 5.55; 2 studies; 85 participants) (very low-certainty). Ginkgo biloba may result in little to no difference in the risk of bleeding or seizures, with no serious adverse effects reported in either group (4 studies; 1154 participants; low-certainty). For the secondary outcomes, one study found that there may be little to no difference between the effects of Ginkgo biloba and placebo on tinnitus loudness measured with audiometric loudness matching at 12 weeks, but the evidence is very uncertain (MD -4.00 (scale -10 to 140 dB), 95% CI -13.33 to 5.33; 1 study; 73 participants) (very low-certainty). One study found that there may be little to no difference between the effects of Ginkgo biloba and placebo on health-related quality of life measured with the Glasgow Health Status Inventory at three months (MD -0.58 (scale 0 to 100), 95% CI -4.67 to 3.51; 1 study; 60 participants) (low-certainty). Ginkgo biloba may not increase the frequency of other adverse effects (gastrointestinal upset, headache, allergic reaction) at three months compared to placebo (risk ratio 0.91, 95% CI 0.52 to 1.60; 4 studies; 1175 participants) (low-certainty). None of the studies reported the other secondary outcomes of tinnitus intrusiveness or changes in depressive symptoms or depression, anxiety symptoms or generalised anxiety. Gingko biloba with concurrent intervention versus concurrent intervention only One study compared Ginkgo biloba with hearing aids to hearing aids only. It assessed the mean difference in the change in Tinnitus Handicap Inventory scores and tinnitus loudness using a 10-point visual analogue scale (VAS) at three months. The study did not report adverse effects, tinnitus intrusiveness, changes in depressive symptoms or depression, anxiety symptoms or generalised anxiety, or health-related quality of life. This was a single, very small study (22 participants) and for all outcomes the certainty of the evidence was very low. We were unable to draw meaningful conclusions from the numerical results.

AUTHORS' CONCLUSIONS

There is uncertainty about the benefits and harms of Ginkgo biloba for the treatment of tinnitus when compared to placebo. We were unable to draw meaningful conclusions regarding the benefits and harms of Ginkgo biloba when used with concurrent intervention (hearing aids). The certainty of the evidence for the reported outcomes, assessed using GRADE, ranged from low to very low. Future research into the effectiveness of Ginkgo biloba in patients with tinnitus should use rigorous methodology. Randomisation and blinding should be of the highest quality, given the subjective nature of tinnitus and the strong likelihood of a placebo response. The CONSORT statement should be used in the design and reporting of future studies. We also recommend the use of validated, patient-centred outcome measures for research in the field of tinnitus.

Preventive Effects of Ginkgo-Extract EGb 761® on Noise Trauma-Induced Cochlear Synaptopathy

Noise trauma-induced loss of ribbon synapses at the inner hair cells (IHC) of the cochlea may lead to hearing loss (HL), resulting in tinnitus. We are convinced that a successful and sustainable therapy of tinnitus has to treat both symptom and cause. One of these causes may be the mentioned loss of ribbon synapses at the IHC of the cochlea. In this study, we investigated the possible preventive and curative effects of the Ginkgo biloba extract EGb 761® on noise-induced synaptopathy, HL, and tinnitus development in Mongolian gerbils (Meriones unguiculatus). To this end, 37 male animals received EGb 761® or placebo orally 3 weeks before (16 animals) or after (21 animals) a monaural acoustic noise trauma (2 kHz, 115 dB SPL, 75 min). Animals' hearing thresholds were determined by auditory brainstem response (ABR) audiometry. A possible tinnitus percept was assessed by the gap prepulse inhibition acoustic startle reflex (GPIAS) response paradigm. Synaptopathy was quantified by cochlear immunofluorescence histology, counting the ribbon synapses of 15 IHCs at 11 different cochlear frequency locations per ear. We found a clear preventive effect of EGb 761® on ribbon synapse numbers with the surprising result of a significant increase in synaptic innervation on the trauma side relative to placebo-treated animals. Consequently, animals treated with EGb 761® before noise trauma did not develop a significant HL and were also less affected by tinnitus compared to placebo-treated animals. On the other hand, we did not see a curative effect (EGb 761® treatment after noise trauma) of the extract on ribbon synapse numbers and, consequently, a significant HL and no difference in tinnitus development compared to the placebo-treated animals. Taken together, EGb 761® prevented noise-induced HL and tinnitus by protecting from noise trauma-induced cochlear ribbon synapse loss; however, in our model, it did not restore lost ribbon synapses.

Circadian Sensitivity of Noise Trauma-Induced Hearing Loss and Tinnitus in Mongolian Gerbils

Noise-induced hearing loss (HL) has a circadian component: In nocturnal mice, hearing thresholds (HT) have a significantly stronger effect to acoustic trauma when induced during the night compared to rather mild effects on hearing when induced during daytime. Here, we investigate whether such effects are also present in diurnal Mongolian gerbils and determined whether trauma-induced HL correlated with the development of a tinnitus percept in these animals. In particular, we investigated the effects of acoustic trauma (2 kHz, 115 dB SPL, 75 min) on HT and tinnitus development in 34 male gerbils exposed either at 9 AM, 1 PM, 5 PM, or 12 PM. HT was measured by acoustic brainstem response audiometry at defined times 1 day before and 1 week after the trauma. Possible tinnitus percepts were assessed behaviorally by the gap prepulse inhibition of the acoustic startle response at defined times 1 day before and 1 week after the trauma. We found daytime-dependent changes due to trauma in mean HT in a frequency-dependent manner comparable to the results in mice, but the results temporally shifted according to respective activity profiles. Additionally, we found linear correlations of these threshold changes with the strength of the tinnitus percept, with the most prominent correlations in the 5 PM trauma group. Taken together, circadian sensitivity of the HT to noise trauma can also be found in gerbils, and tinnitus strength correlates most strongly with HL only when the trauma is applied at the most sensitive times, which seem to be the evening.

Plant-derived nootropics and human cognition: A systematic review

Substances with modulatory capabilities on certain aspects of human cognition have been revered as nootropics from the dawn of time. The plant kingdom provides most of the currently available nootropics of natural origin. Here, in this systematic review, we aim to provide state-of-the-art information regarding proven and unproven effects of plant-derived nootropics (PDNs) on human cognition in conditions of health and disease. Six independent searches, one for each neurocognitive domain (NCD), were performed in parallel using three independent scientific library databases: PubMed, Cochrane and Scopus. Only scientific studies and systematic reviews with humans published between January 2000 and November 2021 were reviewed, and 256 papers were included. Ginkgo biloba was the most relevant nootropic regarding perceptual and motor functions. Bacopa monnieri improves language, learning and memory. Withania somnifera (Ashwagandha) modulates anxiety and social-related cognitions. Caffeine enhances attention and executive functions. Together, the results from the compiled studies highlight the nootropic effects and the inconsistencies regarding PDNs that require further research.Supplemental data for this article is available online at https://doi.org/10.1080/10408398.2021.2021137.

Pharmacologic treatments in preclinical tinnitus models with special focus on Ginkgo biloba leaf extract EGb 761®

Tinnitus is defined as the perception of sound in the absence of external acoustic stimuli. Frequent comorbidities or associated factors are depression, anxiety, concentration problems, insomnia, resignation, helplessness, headache, bruxism, or social isolation, just to name a few. Although many therapeutic approaches have already been tested with varying success, there still is no cure available for tinnitus. The search for an effective treatment has been hampered by the fact that the mechanisms of tinnitus development are still not fully understood, although several models are available and discussed in this review. Our review will give a brief overview about preclinical models, presenting the heterogeneity of tinnitus sub-types depending on the different inner ear and brain structures involved in tinnitus etiology and pathogenesis. Based on these models we introduce the different target structures and transmitter systems implicated in tinnitus development and provide an extensive overview on preclinical drug-based therapeutic approaches that have been explored in various animal models. As the special extract from Ginkgo biloba leaves EGb 761® has been the most widely tested drug in both non-clinical tinnitus models as well as in clinical trials, a special focus will be given to EGb 761®. The efficacy of terpene lactones, flavone glycosides and proanthocyanidines with their distinct contribution to the overall efficacy profile of the multi-constituent drug EGb 761® will be discussed.

Salicylate-Induced Changes in Hearing Thresholds in Mongolian Gerbils Are Correlated With Tinnitus Frequency but Not With Tinnitus Strength

Tinnitus is an auditory phantom percept without external sound sources. Despite the high prevalence and tinnitus-associated distress of affected patients, the pathophysiology of tinnitus remains largely unknown, making prevention and treatments difficult to develop. In order to elucidate the pathophysiology of tinnitus, animal models are used where tinnitus is induced either permanently by noise trauma or transiently by the application of salicylate. In a model of trauma-induced tinnitus, we have suggested a central origin of tinnitus-related development of neuronal hyperactivity based on stochastic resonance (SR). SR refers to the physiological phenomenon that weak subthreshold signals for given sensors (or synapses) can still be detected and transmitted if appropriate noise is added to the input of the sensor. The main objective of this study was to characterize the neurophysiological and behavioral effects during salicylate-induced tinnitus and compare these to the conditions within the trauma model. Our data show, in line with the pharmacokinetics, that hearing thresholds generally increase 2 h after salicylate injections. This increase was significantly stronger within the region of best hearing compared to other frequencies. Furthermore, animals showed behavioral signs of tinnitus during that time window and frequency range as assessed by gap prepulse inhibition of the acoustic startle reflex (GPIAS). In contrast to animals with noise trauma-induced tinnitus, salicylate-induced tinnitus animals showed no correlation between hearing thresholds and behavioral signs of tinnitus, indicating that the development of tinnitus after salicylate injection is not based on SR as proposed for the trauma model. In other words, salicylate-induced tinnitus and noise trauma-induced tinnitus are not based on the same neurophysiological mechanism.

Effectiveness of Tinnitan Duo® in Subjective Tinnitus with Emotional Affectation: A Prospective, Interventional Study

To assess the effectiveness of a food supplement (Tinnitan Duo®) containing 5-hydroxytryptophan, Ginkgo biloba, magnesium, melatonin, vitamin B5 and B6, and zinc at improving tinnitus response and intensity. Prospective, single-center interventional study including patients with subjective tinnitus and emotional affectation. The primary endpoint was the change in the Tinnitus Handicap Inventory (THI) total score and the emotional subscale after 3 months of treatment. Secondary endpoints were the change from baseline to month 3 in (1) the Tinnitus Distress Rating (TDR) scale, and (2) in hearing status, and the safety profile of patients throughout the study. Sixty-one patients were included, and 29 completed the study. The THI total score was significantly reduced after 3 months of treatment in the per-protocol (PP, all the patients with no major protocol deviations) and intention-to-treat (ITT) populations (-15.7 and -7.5, respectively; p = 0.001). The emotional subscale score significantly decreased after 3 months of treatment by -5.6 in the PP (p = 0.001) and by -2.6 in the ITT populations (p = 0.001). Perceived tinnitus loudness significantly decreased after 3 months of treatment (p = 0.001). The audiogram showed no significant changes in hearing status after 3 months of treatment. Of the five adverse events (AEs) reported, all were mild or moderate, and three were related to the study treatment (two headaches and one dizziness). This new food supplement was associated with an improved tinnitus-related emotional affectation and with a good safety profile.

Tinnitus development is associated with synaptopathy of inner hair cells in Mongolian gerbils

Human hearing loss (HL) is often accompanied by comorbidities like tinnitus, which is affecting up to 15% of the adult population. Rodent animal studies could show that tinnitus may not only be a result of apparent HL due to cochlear hair cell damage but can also be a consequence of synaptopathy at the inner hair cells (IHCs) already induced by moderate sound traumata. Here, we investigate synaptopathy previously shown in mice in our animal model, the Mongolian gerbil, and relate it to behavioral signs of tinnitus. Tinnitus was induced by a mild monaural acoustic trauma leading to monaural noise induced HL in the animals, quantified by auditory brainstem response (ABR) audiometry. Behavioral signs of tinnitus percepts were detected by measurement of prepulse inhibition of the acoustic startle response in a gap-noise paradigm. Fourteen days after trauma, the cochleae of both ears were isolated, and IHC synapses were counted within several spectral regions of the cochlea. Behavioral signs of tinnitus were only found in animals with IHC synaptopathy, independent of type of HL. On the other hand, animals with apparent HL but without behavioral signs of tinnitus showed a reduction in amplitudes of ABR waves I&II but no significant changes in the number of synapses at the IHC. We conclude-in line with the literature-that HL is caused by damage to the IHC or by other reasons but that the development of tinnitus, at least in our animal model, is closely linked to synaptopathy at the IHC.

Therapeutic effects of metformin for noise induced hearing loss

OBJECTIVE

This study aimed to investigate the healing effect of metformin on noise induced hearing loss (NIHL) by measuring audiological, biochemical and histological parameters.

MATERIALS AND METHODS

32 rats were divided into four groups (Group 1: Noise, Group 2: Noise + Metformin, Grup 3: Metformin, Grup 4: Control). Broadband noise was applied to Group 1 and Group 2 after basal measurements. Measuring audiological (distortion product otoacoustic emission (DPOAE) and Auditory Brainstem Response (ABR)), biochemical (total antioxidant status (TAS), total oxidant status (TOS), oxidative status index (OSI), DNA damage, IL-1 beta, IL-6, TNF alfa, HSF-1 and COX-2) and histological parameters.

RESULTS

Group 2 had significant decreases in ABR thresholds on day 7 and day 14 compared to day 1. DPOAE values of Group 2 on the 7th and 14th days were significantly higher than the post-noise levels. DNA damage, TOS and OSI values of Group 1 were significantly higher than the other groups. The Cox-2 value of Group 1 was higher than all other groups. The HSF-1 value of Group 2 was significantly higher than that of Group 1. In terms of IL-1 Beta, IL-6 and TNF-alpha values, there was no significant difference between groups 2, 3 and 4 and these values were significantly lower than group 1. In histopathological results of our study, no significant difference was found between the groups being exposed to noise and the control group.

CONCLUSION

This study showed that early period of Metformin treatment has therapeutic effect on NIHL.

Endophytes from Ginkgo biloba and their secondary metabolites

Ginkgo biloba is a medicinal plant which contains abundant endophytes and various secondary metabolites. According to the literary about the information of endophytics from Ginkgo biloba, Chaetomium, Aspergillus, Alternaria, Penicillium and Charobacter were isolated from the root, stem, leaf, seed and bark of G. biloba. The endophytics could produce lots of phytochemicals like flavonoids, terpenoids, and other compounds. These compounds have antibacteria, antioxidation, anticardiovascular, anticancer, antimicrobial and some novel functions. This paper set forth the development of active extracts isolated from endophytes of Ginkgo biloba and will help to improve the resources of Ginkgo biloba to be used in a broader field.

Effects of D-methionine in mice with noise-induced hearing loss mice

Objective

To study the effects of D-methionine in a mouse model of noise-induced hearing loss (NIHL).

Methods

We investigated changes in auditory function and microscopic cochlear structure in a mouse model of NIHL, and carried out 4-hydroxynonenal (4-HNE) immunostaining and terminal deoxynucleotidyl transferase dUTP nick-end labeling, and examined expression levels of connexins 26 and 30 by western blot.

Results

The auditory brainstem response threshold was significantly increased by noise exposure. Noise exposure also damaged the inner and particularly the outer hair cells in the cochlear basement membrane, while histochemistry demonstrated only scattered loss of hair cells in the basement membrane in mice treated with D-methionine before or after noise exposure. D-methionine inhibited apoptosis in the cochlear basement membrane, stria vascularis, and spiral ligament. 4-HNE expression in the basement membrane, stria vascularis, and spiral collateral ligament was increased by noise exposure, but this increase was attenuated by D-methionine. Connexin 26 and connexin 30 expression levels were reduced by noise exposure, and this effect was similarly attenuated by D-methionine administered either before or after noise exposure.

Conclusion

D-methionine administered before or after noise exposure could rescue NIHL by protecting cochlear morphology, inhibiting apoptosis, and maintaining connexin 26 and 30 expression.

[Vascular mechanisms in Meniere's disease]

Meniere's disease (MD) is chronic multifactorial medical condition caused by endolymphatic hydrops, which etiology is unclear. This review highlights possible vascular mechanisms of MD. Impairment of vascular regulation, further ischemic damage of labyrinth and venous drainage pathology could lead to endolymphatic hydrops. Epidemiologic studies reveal high comorbidity of MD and migraine. Both diseases could be the result of trigeminovascular dysfunction. Betahistine, the medication with vascular effect, is widely used in treatment of MD, the effectiveness of calcium channel blockers is evaluated. Keywords: vertigo, Meniere's disease, endolymphatichydrops, migraine, vascular mechanisms, betahistine.

Traditional oriental medicine for sensorineural hearing loss: Can ethnopharmacology contribute to potential drug discovery?

ETHNOPHARMACOLOGICAL RELEVANCE

In Traditional Oriental Medicine (TOM), the development of hearing pathologies is related to an inadequate nourishment of the ears by the kidney and other organs involved in regulation of bodily fluids and nutrients. Several herbal species have historically been prescribed for promoting the production of bodily fluids or as antiaging agents to treat deficiencies in hearing.

AIM OF REVIEW

The prevalence of hearing loss has been increasing in the last decade and is projected to grow considerably in the coming years. Recently, several herbal-derived products prescribed in TOM have demonstrated a therapeutic potential for acquired sensorineural hearing loss and tinnitus. Therefore, the aims of this review are to provide a comprehensive overview of the current known efficacy of the herbs used in TOM for preventing different forms of acquired sensorineural hearing loss and tinnitus, and associate the traditional principle with the demonstrated pharmacological mechanisms to establish a solid foundation for directing future research.

METHODS

The present review collected the literature related to herbs used in TOM or related compounds on hearing from Chinese, Korean, and Japanese herbal classics; library catalogs; and scientific databases (PubMed, Scopus, Google Scholar; and Science Direct).

RESULTS

This review shows that approximately 25 herbal species and 40 active compounds prescribed in TOM for hearing loss and tinnitus have shown in vitro or in vivo beneficial effects for acquired sensorineural hearing loss produced by noise, aging, ototoxic drugs or diabetes. The inner ear is highly vulnerable to ischemia and oxidative damage, where several TOM agents have revealed a direct effect on the auditory system by normalizing the blood supply to the cochlea and increasing the antioxidant defense in sensory hair cells. These strategies have shown a positive impact on maintaining the inner ear potential, sustaining the production of endolymph, reducing the accumulation of toxic and inflammatory substances, preventing sensory cell death and preserving sensory transmission. There are still several herbal species with demonstrated therapeutic efficacy whose mechanisms have not been deeply studied and others that have been traditionally used in hearing loss but have not been tested experimentally. In clinical studies, Ginkgo biloba, Panax ginseng, and Astragalus propinquus have demonstrated to improve hearing thresholds in patients with sensorineural hearing loss and alleviated the symptoms of tinnitus. However, some of these clinical studies have been limited by small sample sizes, lack of an adequate control group or contradictory results.

CONCLUSIONS

Current therapeutic strategies have proven that the goal of the traditional oriental medicine principle of increasing bodily fluids is a relevant approach for reducing the development of hearing loss by improving microcirculation in the blood-labyrinth barrier and increasing cochlear blood flow. The potential benefits of TOM agents expand to a multi-target approach on different auditory structures of the inner ear related to increased cochlear blood flow, antioxidant, anti-inflammatory, anti-apoptotic and neuroprotective activities. However, more research is required, given the evidence is very limited in terms of the mechanism of action at the preclinical in vivo level and the scarce number of clinical studies published.

Optimization of Ultrasound-Assisted Extraction Followed by Macroporous Resin Purification for Maximal Recovery of Functional Components and Removal of Toxic Components from Ginkgo biloba Leaves

In the present study, the process of ultrasound-assisted extraction (UAE) followed by macroporous resin purification was successfully developed to achieve maximal recovery of functional components (flavonoids and ginkgolides) with minimal contents of toxic components (alkylphenols) from Ginkgo biloba leaves. Three effective extracted factors including HAc%, EtOH%, and UAE power were screened by Plackett–Burman design (PBD). The important variables were further optimized by rotatable central composite design (RCCD). By combination of PBD and RCCD, the resulting optimal UAE conditions were as follows: HAc% of 1.8%, EtOH% of 63%, ultrasound power of 303 W, G. biloba leaves powder amount of 1.0 g (solvent-to-solid ratio 40 mL/g), particle size of 60 mesh, extraction time of 40 min, and extraction temperature of 45°C. Under the optimum conditions, the yield of flavonoids was 25.1 ± 0.81 mg/g, ginkgolides was 10.6 ± 0.57 mg/g, and alkylphenols was 3.96 ± 0.31 mg/g. Moreover, the further enriching the functional components and removing toxic components from the obtained extracts of G. biloba leaves using the above optimum UAE condition was successfully achieved by macroporous resin DA-201. After column adsorption and desorption on DA-201, the content of total flavonoids was 36.51 ± 1.53%, ginkgolides was 13.24 ± 0.85%, and alkylphenols was 7.0 ± 1.0 μg/g from the obtained dry extracts (drug to extract ratio of 45-50:1) of G. biloba leaves which were complied with Chinese pharmacopoeias.

[The diagnostics and treatment of tympanophonia]

Tympanophonia can be a consequence of a variety of diseases and pathological conditions diagnostics of which encounters difficulties. The comprehensive clinical examination of the patient is necessary to determine the cause of tympanophonia including elucidation of the following characteristics: initial (acute or gradual) sensation of sound in the ear(s), duration of persisting clinical manifestations, the presence of an acoustic or craniocerebral injury, characteristics of the noise, viz. continuous or intermittent, clicking sounds, paroxysmal or pulsed noise (synchronous with the heart beating), fluctuating, audible to the patient alone or to the surrounding people as well, unilateral and bilateral noises (either symmetric or asymmetric), perception of noise in the head rather than ears., high- and low-pitched noise together with the accompanying neurological symptoms. The analysis of these characteristics makes it possible to differentiate between objective and subjective sensation of noise in the ear(s), determine the amount of additional studies needed for the evaluatio of the conditions of a given patient, identify the possible cause of tympanophonia, establish the nosological diagnosis, and distinguish a group of the patients in need of emergency otological management.

Multi-Response Optimization of Ultrasonic Assisted Enzymatic Extraction Followed by Macroporous Resin Purification for Maximal Recovery of Flavonoids and Ginkgolides from Waste Ginkgo biloba Fallen Leaves

In the present study, the process of ultrasonic assisted enzymatic extraction (UAEE), followed by macroporous resin purification, was successfully developed to achieve maximal recovery of flavonoids and ginkgolides from Ginkgo biloba fallen leaves (GBFL). Three effective extracted factors, including UAE power, EtOH%, and the amount of cellulase were screened by Plackett–Burman design (PBD). The important variables were further optimized by rotatable central composite design (RCCD). After the combination of PBD and RCCD, the resulting optimal UAEE conditions were as follows: UAE power of 218 W; EtOH% of 68%; the amount of cellulase of 8.4 mg; UAE temperature of 40 °C; UAE time of 20 min; pH of 5.0; and, sample particle size of 40 mesh. Under the optimum conditions; the yields of flavonoids were 0.74 ± 0.05% (n = 3) and ginkgolides was 0.42 ± 0.06% (n = 3), which were close to the predicted values. Moreover, the further enriching flavonoids and ginkgolides from the obtained GBFL extracts using the above optimum UAEE condition was successfully achieved by macroporous resin DA-201. After column adsorption and desorption on DA-201; the percentage of total flavonoids was (25.36 ± 1.03)%; ginkgolides was (12.43 ± 0.85)% and alkylphenols was (0.003 ± 0.0005)% from the obtained dry extracts of GBFL which were complied with Chinese pharmacopoeias. Therefore, the present study provided a convenient and efficient method for extraction and purification of flavonoids and ginkgolides from waste GBFL.

A New Statistical Approach for the Evaluation of Gap-prepulse Inhibition of the Acoustic Startle Reflex (GPIAS) for Tinnitus Assessment

Background: An increasingly used behavioral paradigm for the objective assessment of a possible tinnitus percept in animal models has been proposed by Turner and coworkers in 2006. It is based on gap-prepulse inhibition (PPI) of the acoustic startle reflex (ASR) and usually referred to as GPIAS. As it does not require conditioning it became the method of choice to study neuroplastic phenomena associated with the development of tinnitus. Objective: It is still controversial if GPIAS is really appropriate for tinnitus screening, as the hypothesis that a tinnitus percept impairs the gap detection ability ("filling-in interpretation" is still questioned. Furthermore, a wide range of criteria for positive tinnitus detection in GPIAS have been used across different laboratories and there still is no consensus on a best practice for statistical evaluation of GPIAS results. Current approaches are often based on simple averaging of measured PPI values and comparisons on a population level without the possibility to perform valid statistics on the level of the single animal. Methods: A total number of 32 animals were measured using the standard GPIAS paradigm with varying number of measurement repetitions. Based on this data further statistical considerations were performed. Results: We here present a new statistical approach to overcome the methodological limitations of GPIAS. In a first step we show that ASR amplitudes are not normally distributed. Next we estimate the distribution of the measured PPI values by exploiting the full combinatorial power of all measured ASR amplitudes. We demonstrate that the amplitude ratios (1-PPI) are approximately lognormally distributed, allowing for parametrical testing of the logarithmized values and present a new statistical approach allowing for a valid and reliable statistical assessment of PPI changes in GPIAS. Conclusion: Based on our statistical approach we recommend using a constant criterion, which does not systematically depend on the number of measurement repetitions, in order to divide animals into a tinnitus and a non-tinnitus group. In particular, we recommend using a constant threshold based on the effect size as criterion, as the effect size, in contrast to the p-value, does not systematically depend on the number of measurement repetitions.

The Protective Effect of Egb 761 Against 3-Nitropropionic Acid-Induced Hearing Loss: The Role of Sirtuin 1

OBJECTIVES

Local administration of 3-nitropropionic acid (3-NP) to the inner ear induces sensorineural hearing loss. Several studies have shown the otoprotective effects of ginkgo biloba extract EGb 761. Moreover, EGb 761 has been reported to activate Sirtuin 1 (SIRT1). The present study was designed to investigate whether EGb 761 prevents 3-NP-induced sensorineural hearing loss and determine its effects on the expression of SIRT1.

METHODS

Sprague Dawley rats were divided into four experimental groups: control group receiving vehicle of 3-NP, EGb group receiving EGb 761, 3-NP group receiving 3-NP, and EGb+3-NP group receiving EGb 761 and 3-NP. EGb 761 was given orally for 5 days. The 3-NP solution was injected into the tympanum 3 days after the start of EGb 761 administration. The auditory brainstem response was recorded before and after the injection. At 4 weeks after the administration of 3-NP or vehicle of 3-NP, cochleae were harvested, and hematoxylin and eosin staining and immunohistochemistry for SIRT1 antibody were performed.

RESULTS

EGb+3-NP group showed significantly lower threshold shifts than 3-NP group. There was a significant preservation of type II fibrocytes and spiral ganglion cells in EGb+3-NP group than in 3-NP group. In EGb+3-NP group, there was a significantly greater number of SIRT1 immunopositive type II fibrocytes and spiral ganglion cells than in 3-NP group. Calculating the percentage of SIRT1 immunoreactive type II fibrocytes and spiral ganglion cells in viable type II fibrocytes and spiral ganglion cells, respectively, EGb+3-NP group showed significantly higher SIRT1 immunoreactive cells than 3-NP group.

CONCLUSION

These results suggest that EGb 761 may prevent hearing loss induced by 3-NP in an acute ototoxic animal model, which appears to be related with SIRT1 expression.

Noise levels, noise annoyance, and hearing-related problems in a dental college

Through a cross-sectional survey and integrated sound level meter, this research examined noise exposure and auditory- and nonauditory-related problems experienced by students of a dentistry college located in the United Arab Emirates (UAE). A structured interview questionnaire was used to examine hearing-related problems, noise annoyance, and awareness of 114 students toward noise. The results showed that maximum noise levels were between 65 and 79 dB(A) with peak levels (high and low frequencies) ranging between 89 and 93 dB(A). Around 80% of the students experienced a certain degree of noise annoyance; 54% reported one of the hearing-related problems; and about 10% claimed to have hearing loss to a certain extent. It is recommended that sound-absorbent materials be used during the construction of dental clinics and laboratories to reduce the noise levels.

Natural products against Alzheimer's disease: Pharmaco-therapeutics and biotechnological interventions

Alzheimer's disease (AD) is a severe, chronic and progressive neurodegenerative disease associated with memory and cognition impairment ultimately leading to death. It is the commonest reason of dementia in elderly populations mostly affecting beyond the age of 65. The pathogenesis is indicated by accumulation of the amyloid-beta (Aβ) plaques and neurofibrillary tangles (NFT) in brain tissues and hyperphosphorylation of tau protein in neurons. The main cause is considered to be the formation of reactive oxygen species (ROS) due to oxidative stress. The current treatment provides only symptomatic relief by offering temporary palliative therapy which declines the rate of cognitive impairment associated with AD. Inhibition of the enzyme acetylcholinesterase (AChE) is considered as one of the major therapeutic strategies offering only symptomatic relief and moderate disease-modifying effect. Other non-cholinergic therapeutic approaches include antioxidant and vitamin therapy, stem cell therapy, hormonal therapy, use of antihypertensive or lipid-lowering medications and selective phosphodiesterase (PDE) inhibitors, inhibition of β-secretase and γ-secretase and Aβ aggregation, inhibition of tau hyperphosphorylation and intracellular NFT, use of nonsteroidal anti-inflammatory drugs (NSAIDs), transition metal chelators, insulin resistance drugs, etanercept, brain-derived neurotrophic factor (BDNF) etc. Medicinal plants have been reported for possible anti-AD activity in a number of preclinical and clinical trials. Ethnobotany, being popular in China and in the Far East and possibly less emphasized in Europe, plays a substantial role in the discovery of anti-AD agents from botanicals. Chinese Material Medica (CMM) involving Chinese medicinal plants has been used traditionally in China in the treatment of AD. Ayurveda has already provided numerous lead compounds in drug discovery and many of these are also undergoing clinical investigations. A number of medicinal plants either in their crude forms or as isolated compounds have exhibited to reduce the pathological features associated with AD. In this present review, an attempt has been made to elucidate the molecular mode of action of various plant extracts, phytochemicals and traditional herbal formulations investigated against AD as reported in various preclinical and clinical tests. Herbal synergism often found in polyherbal formulations were found effective to combat disease heterogeneity as found in complex pathogenesis of AD. Finally a note has been added to describe biotechnological improvement, genetic and genomic resources and mathematical and statistical techniques for empirical model building associated with anti-AD plant secondary metabolites and their source botanicals.

Therapeutic Value of Ginkgo biloba Extract EGb 761® in an Animal Model (Meriones unguiculatus) for Noise Trauma Induced Hearing Loss and Tinnitus

Noise induced hearing loss (NIHL) is a common disease in modern societies and may lead to maladaptations within the auditory system that finally result in subjective tinnitus. Available therapies may only alleviate the symptoms rather than restore normal hearing. In a previous study we demonstrated that the prophylactic application of Ginkgo biloba extract EGb 761^® significantly reduces NIHL and tinnitus development in our Mongolian gerbil (Meriones unguiculatus) animal model. Here, we tested whether the application of EGb 761^® has beneficial effects after the formation of permanent NIHL and tinnitus. To this end we monitored the therapeutic effects of EGb 761^® on noise trauma-induced changes in signal processing within the auditory system of our animal model by behavioral (acoustic startle response, ASR) and electrophysiological approaches (auditory brainstem responses, ABR). We found that–in contrast to vehicle–three weeks of daily oral EGb 761^® treatment (100 mg/kg body weight) led to a restoration of hearing thresholds back to pre-trauma conditions. In addition, all 9 animals that displayed behavioral signs of subjective tinnitus showed improvement, with 7 of them showing complete relief of tinnitus symptoms during the time of EGb 761^® treatment. After discontinuation of EGb 761^® treatment, tinnitus related behavior reappeared in all but one of these animals while auditory thresholds remained restored. A detailed analysis of ABR waves revealed that EGb 761^® treatment did not simply change auditory processing back to pre-trauma conditions, but led to subtle changes of ABR wave amplitude and latency at different levels of the auditory pathway, with an overall increase of response to low stimulus intensities and a decrease at high intensities. The functional relevance of these changes may be the observed improvement of hearing thresholds while at the same time suppression of responses to high stimulus intensities may point to a global inhibitory mechanism that counteracts tinnitus.

Ginkgo biloba extract promotes osteogenic differentiation of human bone marrow mesenchymal stem cells in a pathway involving Wnt/β-catenin signaling

Human bone marrow derived mesenchymal stem cells (BM-MSCs) are a novel cell source used in stem cell therapy to treat bone diseases owing to their high potential to differentiate into osteoblasts. Effective induction of osteogenic differentiation from human BM-MSCs is critical to fulfill their therapeutic potential. In this study, Ginkgo biloba extract (GBE), a traditional herbal medicine, was used to stimulate the proliferation and osteogenic differentiation of human BM-MSCs. The present study revealed that GBE improved the proliferation and osteogenesis of human BM-MSCs in a dose-dependent manner in the range 25-75 mg/l, as indicated by alkaline phosphatase (ALP) activity and calcium content. However, such effect was decreased or inhibited at 100mg/l or higher. The dose-dependent improvement in osteogenesis of human BM-MSCs by GBE was further confirmed by the dose-dependent upregulation of marker genes, osteopontin (OPN) and Collagen I. The increased osteoprotegerin (OPG) expression and minimal expression of receptor activator of nuclear factor-κB ligand (RANKL) suggested that GBE also inhibited osteoclastogenesis of human BM-MSCs. Further mechanistic study demonstrated that the transcriptional levels of bone morphogenetic protein 4 (BMP4) and runt-related transcription factor 2 (RUNX2) in the BMP signaling, β-catenin and Cyclin D1 in the Wnt/β-catenin signaling, increased significantly during GBE-promoted osteogenesis. Meanwhile, loss-of-function assay with the signaling inhibitor(s) confirmed that the BMP and Wnt/β-catenin signaling pathways were indispensable during the GBE-promoted osteogenesis, suggesting that GBE improved osteogenesis via upregulation of the BMP and Wnt/β-catenin signaling. The present study proposed GBE to be used to upregulate the osteogenic differentiation of human BM-MSCs for new bone formation in BM-MSC-based cell therapy, which could provide an attractive and promising treatment for bone disorders.

Deep brain stimulation in tinnitus: current and future perspectives

Chronic tinnitus, also known as ringing in the ears, affects up to 15% of the adults and causes a serious socio-economic burden. At present, there is no treatment available which substantially reduces the perception of this phantom sound. In the past few years, preclinical and clinical studies have unraveled central mechanisms involved in the pathophysiology of tinnitus, replacing the classical periphery-based hypothesis. In subcortical auditory and non-auditory regions, increased spontaneous activity, neuronal bursting and synchrony were found. When reaching the auditory cortex, these neuronal alterations become perceptually relevant and consequently are perceived as phantom sound. A therapy with a potential to counteract deeply located pathological activity is deep brain stimulation, which has already been demonstrated to be effective in neurological diseases such as Parkinson's disease. In this review, several brain targets are discussed as possible targets for deep brain stimulation in tinnitus. The potential applicability of this treatment in tinnitus is discussed with examples from the preclinical field and clinical case studies.

[Tanakan as a multimodal cytoprotective factor in general medicine (part II)]

The second section of the review provides an update of the data on mechanisms of action of a standardized extract of Ginkgo biloba EGb761® (tanakan) and its efficacy in treatment of depression, pain, complications of diabetes, Parkinson disease, tinnitus and dizziness, reproductive dysfunction. Updated data enable to use EGb761® (tanakan) as a highly-effective cytoprotective agent in treatment of cardiovascular, degenerative and metabolic diseases of the nervous system, inner ear disturbances (tinnitus), dysfunction of reproductive system as well as in prevention and treatment of stress-induced disorders.