Coenzyme Q10 ameliorates oxidative stress and prevents mitochondrial alteration in ischemic retinal injury

Administration of Bicarbonate Protects Mitochondria, Rescues Retinal Ganglion Cells, and Ameliorates Visual Dysfunction Caused by Oxidative Stress

Oxidative stress is a key factor causing mitochondrial dysfunction and retinal ganglion cell (RGC) death in glaucomatous neurodegeneration. The cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling pathway is involved in mitochondrial protection, promoting RGC survival. Soluble adenylyl cyclase (sAC) is a key regulator of the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling pathway, which is known to protect mitochondria and promote RGC survival. However, the precise molecular mechanisms connecting the sAC-mediated signaling pathway with mitochondrial protection in RGCs against oxidative stress are not well characterized. Here, we demonstrate that sAC plays a critical role in protecting RGC mitochondria from oxidative stress. Using mouse models of oxidative stress induced by ischemic injury and paraquat administration, we found that administration of bicarbonate, as an activator of sAC, protected RGCs, blocked AMP-activated protein kinase activation, inhibited glial activation, and improved visual function. Moreover, we found that this is the result of preserving mitochondrial dynamics (fusion and fission), promoting mitochondrial bioenergetics and biogenesis, and preventing metabolic stress and apoptotic cell death. Notably, the administration of bicarbonate ameliorated mitochondrial dysfunction in RGCs by enhancing mitochondrial biogenesis, preserving mitochondrial structure, and increasing ATP production in oxidatively stressed RGCs. These findings suggest that activating sAC enhances the mitochondrial structure and function in RGCs to counter oxidative stress, consequently promoting RGC protection. We propose that modulation of the sAC-mediated signaling pathway has therapeutic potential acting on RGC mitochondria for treating glaucoma and other retinal diseases.

Coenzyme Q10 eyedrops conjugated with vitamin E TPGS alleviate neurodegeneration and mitochondrial dysfunction in the diabetic mouse retina

Diabetic retinopathy (DR) is a leading cause of blindness and vision impairment worldwide and represents one of the most common complications among diabetic patients. Current treatment modalities for DR, including laser photocoagulation, intravitreal injection of corticosteroid, and anti-vascular endothelial growth factor (VEGF) agents, target primarily vascular lesions. However, these approaches are invasive and have several limitations, such as potential loss of visual function, retinal scars and cataract formation, and increased risk of ocular hypertension, vitreous hemorrhage, retinal detachment, and intraocular inflammation. Recent studies have suggested mitochondrial dysfunction as a pivotal factor leading to both the vascular and neural damage in DR. Given that Coenzyme Q10 (CoQ10) is a proven mitochondrial stabilizer with antioxidative properties, this study investigated the effect of CoQ10 eyedrops [in conjunction with vitamin E d-α-tocopheryl poly(ethylene glycol) 1000 succinate (TPGS)] on DR-induced neurodegeneration using a type 2 diabetes mouse model (C57BLKsJ-db/db mice). Utilizing a comprehensive electroretinography protocol, supported by immunohistochemistry, our results revealed that topical application of CoQ10 eyedrops conjugated with vitamin E TPGS produced a neuroprotective effect against diabetic-induced neurodegeneration by preserving the function and histology of various retinal neural cell types. Compared to the control group, mice treated with CoQ10 exhibited thicker outer and inner nuclear layers, higher densities of photoreceptor, cone cell, and rod-bipolar cell dendritic boutons, and reduced glial reactivity and microglial cell density. Additionally, the CoQ10 treatment significantly alleviated retinal levels of MMP-9 and enhanced mitochondrial function. These findings provide further insight into the role of mitochondrial dysfunction in the development of DR and suggest CoQ10 eyedrops, conjugated with vitamin E TPGS, as a potential complementary therapy for DR-related neuropathy.

Addressing neurodegeneration in glaucoma: Mechanisms, challenges, and treatments

Glaucoma is the leading cause of irreversible blindness globally. The disease causes vision loss due to neurodegeneration of the retinal ganglion cell (RGC) projection to the brain through the optic nerve. Glaucoma is associated with sensitivity to intraocular pressure (IOP). Thus, mainstay treatments seek to manage IOP, though many patients continue to lose vision. To address neurodegeneration directly, numerous preclinical studies seek to develop protective or reparative therapies that act independently of IOP. These include growth factors, compounds targeting metabolism, anti-inflammatory and antioxidant agents, and neuromodulators. Despite success in experimental models, many of these approaches fail to translate into clinical benefits. Several factors contribute to this challenge. Firstly, the anatomic structure of the optic nerve head differs between rodents, nonhuman primates, and humans. Additionally, animal models do not replicate the complex glaucoma pathophysiology in humans. Therefore, to enhance the success of translating these findings, we propose two approaches. First, thorough evaluation of experimental targets in multiple animal models, including nonhuman primates, should precede clinical trials. Second, we advocate for combination therapy, which involves using multiple agents simultaneously, especially in the early and potentially reversible stages of the disease. These strategies aim to increase the chances of successful neuroprotective treatment for glaucoma.

Optic Nerve Neuroprotection in Glaucoma: A Narrative Review

In recent years, researchers have been interested in neuroprotective therapies as a cutting-edge therapeutic strategy to treat neurodegenerative disorders by shielding the brain system from harmful events. Millions of individuals worldwide suffer from glaucoma, an ocular neurodegenerative disease characterized by gradual excavation of the optic nerve head, retinal axonal damage, and consequent visual loss. The pathology's molecular cause is still mostly unknown, and the current treatments are not able to alter the disease's natural progression. Thus, the modern approach to treating glaucoma consists of prescribing medications with neuroprotective properties, in line with the treatment strategy suggested for other neurodegenerative diseases. For this reason, several naturally derived compounds, including nicotinamide and citicoline, have been studied throughout time to try to improve glaucoma management by exploiting their neuroprotective properties. The purpose of this review is to examine the naturally derived compounds that are currently utilized in clinical practice for neuroprotection in glaucomatous patients based on scientific data, emphasizing these compounds' pivotal mechanism of action as well as their proven therapeutic and neuroprotective benefits.

Comparison of Glutathione Nanoparticles, CoEnzyme Q10, and Fish Oil for Prevention of Oxygen-Induced Retinopathy in Neonatal Rats

Notch ligands and receptors are important for cell specification and angiogenesis, but their role in oxygen-induced retinopathy (OIR) is not well studied. Delta-like ligand (DLL)-4/Notch inhibits angiogenesis, while Jagged-1/Notch promotes angiogenesis. We tested the hypothesis that early supplementation with antioxidants and/or fish oil curtails severe OIR by inducing DLL-4/Notch and reducing Jagged-1/Notch. Newborn rats were exposed to brief intermittent hypoxia (IH) during hyperoxia, during which they received daily oral supplements of (1) fish oil, (2) coenzyme Q10 (CoQ10) in olive oil (OO), (3) glutathione nanoparticles (nGSH), (4) fish oil + CoQ10, or (5) OO (controls) from birth (P0) to P14. At P14, the pups were placed in room air (RA) until P21, with no further treatment. Oxidative stress, apoptosis, ocular histopathology, and Notch signaling were assessed. Neonatal IH resulted in severe retinal damage consistent with retinopathy of prematurity (ROP). Retinal damage was associated with induced oxidative stress and Jagged-1/Notch signaling, as well as reduced DLL-4/Notch signaling. All treatments reversed these outcomes, but nGSH produced the most beneficial outcomes. Severe OIR promoted the induction of Jagged-1/Notch and curtailed DLL-4/Notch, which was an effect that could be reversed with nGSH supplementation. These findings may indicate a potential alternate pathway for ROP treatment and/or prevention.

Activating soluble adenylyl cyclase protects mitochondria, rescues retinal ganglion cells, and ameliorates visual dysfunction caused by oxidative stress

Oxidative stress is a key factor causing mitochondrial dysfunction and retinal ganglion cell (RGC) death in glaucomatous neurodegeneration. The cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling pathway is involved in mitochondrial protection, promoting RGC survival. Soluble adenylyl cyclase (sAC) is one of the key regulators of the cAMP/PKA signaling pathway. However, the precise molecular mechanisms underlying the sAC-mediated signaling pathway and mitochondrial protection in RGCs that counter oxidative stress are not well characterized. Here, we demonstrate that sAC plays a critical role in protecting RGC mitochondria from oxidative stress. Using mouse models of oxidative stress, we found that activating sAC protected RGCs, blocked AMP-activated protein kinase activation, inhibited glial activation, and improved visual function. Moreover, we found that this is the result of preserving mitochondrial dynamics (fusion and fission), promoting mitochondrial bioenergetics and biogenesis, and preventing metabolic stress and apoptotic cell death in a paraquat oxidative stress model. Notably, sAC activation ameliorated mitochondrial dysfunction in RGCs by enhancing mitochondrial biogenesis, preserving mitochondrial structure, and increasing ATP production in oxidatively stressed RGCs. These findings suggest that activating sAC enhances the mitochondrial structure and function in RGCs to counter oxidative stress, consequently promoting RGC protection. We propose that modulation of the sAC-mediated signaling pathway has therapeutic potential acting on RGC mitochondria for treating glaucoma and other retinal diseases.

Trolox aids coenzyme Q10 in neuroprotection against NMDA induced damage via upregulation of VEGF in rat model of glutamate excitotoxicity

Glutamate induced damage to retinal ganglion cells (RGCs) requires tight physiological regulation of the N-methyl-D-aspartate (NMDA) receptors. Previously, studies have demonstrated the neuroprotective abilities of antioxidants like coenzyme Q10 (CoQ10) and vitamin E analogs like α-tocopherol against neuropathies resulting from NMDA insult, but have failed to shed light on the effect of CoQ10 and trolox, a hydrophilic analog of vitamin E, on glaucomatous neurodegeneration. In the current study, we wanted to investigate whether the combined effect of trolox with CoQ10 could alleviate NMDA-induced death of retinal cells while also trying to elucidate the underlying mechanism in relation to the yet unexplained role of vascular endothelial growth factor (VEGF) in NMDA-mediated excitotoxicity. After successful NMDA-induced degeneration, we followed it up with the treatment of combination of Trolox and CoQ10. The structural damage by NMDA was repaired significantly and retina retained structural integrity comparable to levels of control in the treatment group of Trolox and CoQ10. Detection of ROS generation after NMDA insult showed that together, Trolox and CoQ10 could significantly bring down the high levels of free radicals while also rescuing mitochondrial membrane potential (MMP). A significant increase in NMDA receptor Grin2A by CoQ10 alone as well as by CoQ10 and trolox was accompanied by a lowered Grin2B receptor expression, suggesting neuroprotective action of Trolox and CoQ10. Subsequently, lowered VEGFR1 and VEGFR2 receptor expression by NMDA treatment also recovered when subjected to combined treatment of Trolox and CoQ10. Western blot analyses also indicated the same whereby Trolox and CoQ10 could increase the diminished levels of phosphorylated VEGFR2. Immunofluorescence studies also indicated a positive correlation between recovered VEGFR2 and NMDAR2A levels and diminished levels of NMDAR2D, confirming the results obtained by RT-PCR analysis. This is the first report in our knowledge that demonstrates the efficacy of trolox in combination with CoQ10 highlighting the importance of maintaining VEGF levels that are lowered in ocular diseases due to NMDA-related toxicities.

Evaluation of the protective effect of coenzyme Q10 on hepatotoxicity caused by acute phosphine poisoning

Background: Aluminum phosphide (AlP) poisoning is prevalent in numerous countries, resulting in high mortality rates. Phosphine gas, the primary agent responsible for AlP poisoning, exerts detrimental effects on various organs, notably the heart, liver and kidneys. Numerous studies have documented the advantageous impact of Coenzyme Q10 (CoQ10) in mitigating hepatic injuries. The objective of this investigation is to explore the potential protective efficacy of CoQ10 against hepatic toxicity arising from AlP poisoning. Method: The study encompassed distinct groups receiving almond oil, normal saline, exclusive CoQ10 (at a dosage of 100 mg/kg), AlP at 12 mg/kg; LD50 (lethal dose for 50%), and four groups subjected to AlP along with CoQ10 administration (post-AlP gavage). CoQ10 was administered at 10, 50, and 100 mg/kg doses via Intraparietal (ip) injections. After 24 h, liver tissue specimens were scrutinized for mitochondrial complex activities, oxidative stress parameters, and apoptosis as well as biomarkers such as aspartate transaminase (AST) and alanine transaminase (ALT). Results: AlP induced a significant decrease in the activity of mitochondrial complexes I and IV, as well as a reduction in catalase activity, Ferric Reducing Antioxidant Power (FRAP), and Thiol levels. Additionally, AlP significantly elevated oxidative stress levels, indicated by elevated reactive oxygen species (ROS) production, and resulted in the increment of hepatic biomarkers such as AST and ALT. Administration of CoQ10 led to a substantial improvement in the aforementioned biochemical markers. Furthermore, phosphine exposure resulted in a significant reduction in viable hepatocytes and an increase in apoptosis. Co-treatment with CoQ10 exhibited a dose-dependent reversal of these observed alterations. Conclusion: CoQ10 preserved mitochondrial function, consequently mitigating oxidative damage. This preventive action impeded the progression of heart cells toward apoptosis.

Oxidative stress in the eye and its role in the pathophysiology of ocular diseases

Oxidative stress occurs through an imbalance between the generation of reactive oxygen species (ROS) and the antioxidant defense mechanisms of cells. The eye is particularly exposed to oxidative stress because of its permanent exposure to light and due to several structures having high metabolic activities. The anterior part of the eye is highly exposed to ultraviolet (UV) radiation and possesses a complex antioxidant defense system to protect the retina from UV radiation. The posterior part of the eye exhibits high metabolic rates and oxygen consumption leading subsequently to a high production rate of ROS. Furthermore, inflammation, aging, genetic factors, and environmental pollution, are all elements promoting ROS generation and impairing antioxidant defense mechanisms and thereby representing risk factors leading to oxidative stress. An abnormal redox status was shown to be involved in the pathophysiology of various ocular diseases in the anterior and posterior segment of the eye. In this review, we aim to summarize the mechanisms of oxidative stress in ocular diseases to provide an updated understanding on the pathogenesis of common diseases affecting the ocular surface, the lens, the retina, and the optic nerve. Moreover, we discuss potential therapeutic approaches aimed at reducing oxidative stress in this context.

Glaucomatous optic neuropathy: Mitochondrial dynamics, dysfunction and protection in retinal ganglion cells

Glaucoma is a leading cause of irreversible blindness worldwide and is characterized by a slow, progressive, and multifactorial degeneration of retinal ganglion cells (RGCs) and their axons, resulting in vision loss. Despite its high prevalence in individuals 60 years of age and older, the causing factors contributing to glaucoma progression are currently not well characterized. Intraocular pressure (IOP) is the only proven treatable risk factor. However, lowering IOP is insufficient for preventing disease progression. One of the significant interests in glaucoma pathogenesis is understanding the structural and functional impairment of mitochondria in RGCs and their axons and synapses. Glaucomatous risk factors such as IOP elevation, aging, genetic variation, neuroinflammation, neurotrophic factor deprivation, and vascular dysregulation, are potential inducers for mitochondrial dysfunction in glaucoma. Because oxidative phosphorylation stress-mediated mitochondrial dysfunction is associated with structural and functional impairment of mitochondria in glaucomatous RGCs, understanding the underlying mechanisms and relationship between structural and functional alterations in mitochondria would be beneficial to developing mitochondria-related neuroprotection in RGCs and their axons and synapses against glaucomatous neurodegeneration. Here, we review the current studies focusing on mitochondrial dynamics-based structural and functional alterations in the mitochondria of glaucomatous RGCs and therapeutic strategies to protect RGCs against glaucomatous neurodegeneration.

The Role of Citicoline and Coenzyme Q10 in Retinal Pathology

Ocular neurodegenerative diseases such as glaucoma, diabetic retinopathy, and age-related macular degeneration are common retinal diseases responsible for most of the blindness causes in the working-age and elderly populations in developed countries. Many of the current treatments used in these pathologies fail to stop or slow the progression of the disease. Therefore, other types of treatments with neuroprotective characteristics may be necessary to allow a more satisfactory management of the disease. Citicoline and coenzyme Q10 are molecules that have neuroprotective, antioxidant, and anti-inflammatory properties, and their use could have a beneficial effect in ocular neurodegenerative pathologies. This review provides a compilation, mainly from the last 10 years, of the main studies that have been published on the use of these drugs in these neurodegenerative diseases of the retina, analyzing the usefulness of these drugs in these pathologies.

Combined use of coenzyme Q10 and citicoline: A new possibility for patients with glaucoma

Glaucoma is the leading cause of irreversible blindness worldwide. Several risk factors have been involved in the pathogenesis of the disease. By now, the main treatable risk factor is elevated intraocular pressure. Nevertheless, some patients, whose intraocular pressure is considered in the target level, still experience a progression of the disease. Glaucoma is a form of multifactorial ocular neurodegeneration with complex etiology, pathogenesis, and pathology. New evidence strongly suggests brain involvement in all aspects of this disease. This hypothesis and the need to prevent glaucomatous progression led to a growing interest in the pharmacological research of new neuroprotective, non-IOP-lowering, agents. The aim of this paper is to report evidence of the usefulness of Coenzyme Q10 and Citicoline, eventually combined, in the prevention of glaucomatous neurodegeneration.

Combined Supplementation of Coenzyme Q10 and Other Nutrients in Specific Medical Conditions

Coenzyme Q₁₀ (CoQ₁₀) is a compound with a crucial role in mitochondrial bioenergetics and membrane antioxidant protection. Despite the ubiquitous endogenous biosynthesis, specific medical conditions are associated with low circulating CoQ₁₀ levels. However, previous studies of oral CoQ₁₀ supplementation yielded inconsistent outcomes. In this article, we reviewed previous CoQ₁₀ trials, either single or in combination with other nutrients, and stratified the study participants according to their metabolic statuses and medical conditions. The CoQ₁₀ supplementation trials in elders reported many favorable outcomes. However, the single intervention was less promising when the host metabolic statuses were worsening with the likelihood of multiple nutrient insufficiencies, as in patients with an established diagnosis of metabolic or immune-related disorders. On the contrary, the mixed CoQ₁₀ supplementation with other interacting nutrients created more promising impacts in hosts with compromised nutrient reserves. Furthermore, the results of either single or combined intervention will be less promising in far-advanced conditions with established damage, such as neurodegenerative disorders or cancers. With the limited high-level evidence studies on each host metabolic category, we could only conclude that the considerations of whether to take supplementation varied by the individuals' metabolic status and their nutrient reserves. Further studies are warranted.

The effect of idebenone and corticosteroid treatment on methanol-induced toxic optic nerve and retinal damage in rats: biochemical and histopathological examination

PURPOSE

To evaluate the therapeutic effects of methylprednisolone, the CoenzymeQ10 (CoQ10) structural analogue idebenone, and both together on the optic nerve (ON) and retinal layers following methanol intoxication in rats with histopathological and biochemical methods.

MATERIALS AND METHODS

This experimental study was conducted with 30 male Wistar rats. The rats were divided into five equal groups depending on the treatment protocol:healthy controls (HC), methanol (M), methanol + methylprednisolone (MM), methanol + idebenone (MI), and methanol + methylprednisolone + idebenone (MMI).Distilled water was provided orally to the HC group, while 20% methanol was administered orally at a dose of 3 g/kg with a nasogastric tube to all rats in groups except the HC group. Four hours later, group MM received 1 mg/kg of intraperitoneal methylprednisolone for 10 days using an insulin syringe, and group MI received 20 mg/kg idebenone by nasogastric catheter for 28 days. MMI group was administered oral idebenone and intraperitoneal methylprednisolone at the same dose. Serum samples were obtained on the 28^th day for biochemical analysis and afterwards the rats were euthanized for histopathological examination and eyes were enucleated. ON was evaluated for circumference thickness, vascularization and number of astrocytes, also retinal layers were examined for structural changes by histopathological examination.

RESULTS

Comparison of the antioxidant and oxidative stress biomarkers between the groups revealed no statistically significant difference (p > 0.05). By histopathological evaluation the most marked results were obtained by MMI group with an improvement of all parameters mentioned. There was no statistically significant difference between MM group and M group for RD score (p = 0.123). In addition, ON vacuolization in MI group (p < 0.001) and ON astrocyte increase in both MI and MMI groups were statistically significantly lower than in M group (p = 0.001, p = 0.001, respectively).

CONCLUSIONS

The early use (within hours) of idebenone and short-term methylprednisolone treatment together may protect against the retinal and ON damage developing after methanol ingestion in rats as guided by the histopathological data.

Degeneration of retina-brain components and connections in glaucoma: Disease causation and treatment options for eyesight preservation

Eyesight is the most important of our sensory systems for optimal daily activities and overall survival. Patients who experience visual impairment due to elevated intraocular pressure (IOP) are often those afflicted with primary open-angle glaucoma (POAG) which slowly robs them of their vision unless treatment is administered soon after diagnosis. The hallmark features of POAG and other forms of glaucoma are damaged optic nerve, retinal ganglion cell (RGC) loss and atrophied RGC axons connecting to various brain regions associated with receipt of visual input from the eyes and eventual decoding and perception of images in the visual cortex. Even though increased IOP is the major risk factor for POAG, the disease is caused by many injurious chemicals and events that progress slowly within all components of the eye-brain visual axis. Lowering of IOP mitigates the damage to some extent with existing drugs, surgical and device implantation therapeutic interventions. However, since multifactorial degenerative processes occur during aging and with glaucomatous optic neuropathy, different forms of neuroprotective, nutraceutical and electroceutical regenerative and revitalizing agents and processes are being considered to combat these eye-brain disorders. These aspects form the basis of this short review article.

Multi-Ingredient Supplement Supports Mitochondrial Health through Interleukin-15 Signaling in Older Adult Human Dermal Fibroblasts

The macroscopic and microscopic deterioration of human skin with age is, in part, attributed to a functional decline in mitochondrial health. We previously demonstrated that exercise attenuated age-associated changes within the skin through enhanced mitochondrial health via IL-15 signaling, an exercise-induced cytokine whose presence increases in circulation following physical activity. The purpose of this investigation was to determine if these mitochondrial-enhancing effects could be mimicked with the provision of a novel multi-ingredient supplement (MIS). Cultured human fibroblasts isolated from older, sedentary women were treated with control media (CON) or CON supplemented with the following active ingredients to create the MIS: coenzyme Q10, alpha lipoic acid, resveratrol, curcumin, zinc, lutein, astaxanthin, copper, biotin, and vitamins C, D, and E. Outcomes were determined following 24 or 72 h of treatment. MIS provision to dermal fibroblasts significantly increased the mRNA abundance of mitochondrial biogenesis activators and downstream IL-15 signaling pathways, and proteins for oxidative phosphorylation subunits and antioxidant defenses. These findings were co-temporal with lower cellular senescence and cytotoxicity following MIS treatment. In summary, MIS supplementation led to exercise-mimetic effects on human dermal fibroblasts and their mitochondria by reproducing the molecular and biochemical effects downstream of IL-15 activation.

Retinal Glutamate Neurotransmission: From Physiology to Pathophysiological Mechanisms of Retinal Ganglion Cell Degeneration

Glutamate neurotransmission and metabolism are finely modulated by the retinal network, where the efficient processing of visual information is shaped by the differential distribution and composition of glutamate receptors and transporters. However, disturbances in glutamate homeostasis can result in glutamate excitotoxicity, a major initiating factor of common neurodegenerative diseases. Within the retina, glutamate excitotoxicity can impair visual transmission by initiating degeneration of neuronal populations, including retinal ganglion cells (RGCs). The vulnerability of RGCs is observed not just as a result of retinal diseases but has also been ascribed to other common neurodegenerative and peripheral diseases. In this review, we describe the vulnerability of RGCs to glutamate excitotoxicity and the contribution of different glutamate receptors and transporters to this. In particular, we focus on the N-methyl-d-aspartate (NMDA) receptor as the major effector of glutamate-induced mechanisms of neurodegeneration, including impairment of calcium homeostasis, changes in gene expression and signalling, and mitochondrial dysfunction, as well as the role of endoplasmic reticular stress. Due to recent developments in the search for modulators of NMDA receptor signalling, novel neuroprotective strategies may be on the horizon.

Damage-Associated Molecular Patterns (DAMPs) in Retinal Disorders

Damage-associated molecular patterns (DAMPs) are endogenous danger molecules released from the extracellular and intracellular space of damaged tissue or dead cells. Recent evidence indicates that DAMPs are associated with the sterile inflammation caused by aging, increased ocular pressure, high glucose, oxidative stress, ischemia, mechanical trauma, stress, or environmental conditions, in retinal diseases. DAMPs activate the innate immune system, suggesting their role to be protective, but may promote pathological inflammation and angiogenesis in response to the chronic insult or injury. DAMPs are recognized by specialized innate immune receptors, such as receptors for advanced glycation end products (RAGE), toll-like receptors (TLRs) and the NOD-like receptor family (NLRs), and purine receptor 7 (P2X7), in systemic diseases. However, studies describing the role of DAMPs in retinal disorders are meager. Here, we extensively reviewed the role of DAMPs in retinal disorders, including endophthalmitis, uveitis, glaucoma, ocular cancer, ischemic retinopathies, diabetic retinopathy, age-related macular degeneration, rhegmatogenous retinal detachment, proliferative vitreoretinopathy, and inherited retinal disorders. Finally, we discussed DAMPs as biomarkers, therapeutic targets, and therapeutic agents for retinal disorders.

Treatment of Glaucoma with Natural Products and Their Mechanism of Action: An Update

Glaucoma is one of the leading causes of irreversible blindness. It is generally caused by increased intraocular pressure, which results in damage of the optic nerve and retinal ganglion cells, ultimately leading to visual field dysfunction. However, even with the use of intraocular pressure-lowering eye drops, the disease still progresses in some patients. In addition to mechanical and vascular dysfunctions of the eye, oxidative stress, neuroinflammation and excitotoxicity have also been implicated in the pathogenesis of glaucoma. Hence, the use of natural products with antioxidant and anti-inflammatory properties may represent an alternative approach for glaucoma treatment. The present review highlights recent preclinical and clinical studies on various natural products shown to possess neuroprotective properties for retinal ganglion cells, which thereby may be effective in the treatment of glaucoma. Intraocular pressure can be reduced by baicalein, forskolin, marijuana, ginsenoside, resveratrol and hesperidin. Alternatively, Ginkgo biloba, Lycium barbarum, Diospyros kaki, Tripterygium wilfordii, saffron, curcumin, caffeine, anthocyanin, coenzyme Q10 and vitamins B3 and D have shown neuroprotective effects on retinal ganglion cells via various mechanisms, especially antioxidant, anti-inflammatory and anti-apoptosis mechanisms. Extensive studies are still required in the future to ensure natural products' efficacy and safety to serve as an alternative therapy for glaucoma.

Histopathological effects of topical coenzyme q 10 + Vit E TPGS in experimental ischemic optic neuropathy

We aimed to create a mechanical optic nerve damage model in rats and to investigate the neuroprotective effects of topical Coenzyme Q10 + Vitamin E TPGS (CoQ10+Vit E) molecule on retinal ganglion cells. In our study, 30 eyes of 20 male Wistar rats were used. Three groups, each consisting of 10 eyes, were formed as control, experimental, and treatment groups. The control group was used to test the formation of optic nerve damage. Topical CoQ10 + Vit E TPGS solution was applied to the rats in the treatment group, one drop twice a day for 3 weeks. On the other hand, physiological drops were applied to the experimental group 2 times a day for 3 weeks. After 3 weeks, the optic nerves of the rats were dissected and examined histopathologically. In electron microscopic examination of the treatment group, it was noted that the myelin sheath in the majority of myelinated nerve fibers and the normal structures of mitochondria, neurotubules, and neurofilaments in the axoplasm were preserved. It was observed that the oligodendrocytes surrounded the myelinated axons. In the experimental group, significant degenerative changes were observed in myelinated nerve fibers in many areas. The number of myelinated axons was significantly increased in the treatment group compared to the experimental group (p = .0028). In the light of the data obtained, the neuroprotective effect of the topically used CoQ10 + Vit E TPGS molecule was found to be histopathologically effective in our experimental study.Abbreviations: NAAION: Nonarteritic anterior ischemic optic neuropathy; CoQ10: Coenzyme q10; CG: Control group; EG: Experimental group; TG: Treatment group.

Polydopamine nanoparticles attenuate retina ganglion cell degeneration and restore visual function after optic nerve injury

Background

Oxidative stress contributes to retina ganglion cells (RGCs) loss in variety of ocular diseases, including ocular trauma, ocular vein occlusion, and glaucoma. Scavenging the excessed reactive oxygen species (ROS) in retinal neurovascular unit could be beneficial to RGCs survival. In this study, a polydopamine (PDA)-based nanoplatform is developed to protect RGCs.

Results

The PDA nanoparticles efficiently eliminate multi-types of ROS, protect endothelia and neuronal cells from oxidative damage, and inhibit microglia activation in retinas. In an optic nerve crush (ONC) model, single intravitreal injection of PDA nanoparticles could significantly attenuate RGCs loss via eliminating ROS in retinas, reducing the inflammatory response and maintaining barrier function of retinal vascular endothelia. Comparative transcriptome analysis of the retina implied that PDA nanoparticles improve RGCs survival probably by altering the expression of genes involved in inflammation and ROS production. Importantly, as a versatile drug carrier, PDA nanoparticles could deliver brimonidine (a neuroprotection drug) to synergistically attenuate RGCs loss and promote axon regeneration, thus restore visual function.

Conclusions

The PDA nanoparticle-based therapeutic nanoplatform displayed excellent performance in ROS elimination, providing a promising probability for treating retinal degeneration diseases.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01199-3.

Dietary Antioxidants in Age-Related Macular Degeneration and Glaucoma

Age-related macular degeneration (AMD) and glaucoma are ophthalmic neurodegenerative diseases responsible for irreversible vision loss in the world population. Only a few therapies can be used to slow down the progression of these diseases and there are no available treatment strategies for reversing the degeneration of the neural retina. In AMD, the pathological process causes the malfunction and damage of the retinal pigmented epithelium and photoreceptors in the macula. In glaucoma, damage of the retinal ganglion cells and their axons is observed and treatment strategies are limited to intraocular pressure lowering. Therefore, other prophylactic and/or therapeutic methods are needed. Oxidative stress is involved in the neurodegenerative process accompanying both AMD and glaucoma; therefore, the use of antioxidant agents would clearly be beneficial, which is supported by the decreased prevalence and progression of AMD in patients adherent to a diet naturally rich in antioxidants. Dietary antioxidants are easily available and their use is based on the natural route of administration. Many preclinical studies both in vitro and using animal models of retinal degeneration showed the efficacy of dietary antioxidants, which was further proved in clinical trials. Resveratrol is beneficial both in AMD and glaucoma animal models, but confirmed only among AMD patients. For AMD, carotenoids and omega-3 fatty acids were also proved to be sufficient in preventing neurodegeneration. For glaucoma, coenzyme Q10 and alpha-lipoic acid showed efficacy for decreasing retinal ganglion cell loss and inhibiting the accompanying destructive processes. Interestingly, the benefits of vitamins, especially vitamin E was not confirmed, neither in preclinical nor in clinical studies.

Coenzyme Q10 Modulates Apoptotic Effects of Chronic Administration of Methadone on NMRI Mouse Hippocampus

OBJECTIVE

Methadone is one of the widely used drug substances prescribed in treatment of opioid dependence and pain management; however, several studies have shown its neurotoxic effects on individuals and animal models. The purpose of this study was to assess neuroprotective effects of Coenzyme Q10 (CoQ10) on neurotoxicity induced by methadone in hippocampus of adult NMRI male mice.

MATERIALS AND METHODS

In this experimental study, 48 adult NMRI male mice were randomly divided into 4 groups (n=12 in each) including Methadone, Methadone with sesame oil, Methadone with CoQ10 and saline. The injections of methadone, saline and sesame oil were performed intraperitoneally for 20 days. 24 hours after last injection, half of the animals in each group (n=6) were randomly assessed for evaluating of spatial memory by radial maze. Following behavioral study, animals were sacrificed, and their brains were removed to evaluate pyknotic cells through histological assessment. The remaining were used to study the expression of Arc, Bax, Bcl-2 and Bdnf genes.

RESULTS

Results of the present study showed that daily administration of methadone increased the number of pyknotic neurons in the CA1 hippocampus and altered the expression of Bax, Bdnf, Arc and Bcl-2. However, it did not alter spatial memory comparing to saline group. CoQ10 treatment significantly reduced the number of pyknotic cells and expression of Bax, Bdnf, Arc when compared to the vehicle group treated by sesame oil. However, the expression of Bcl-2 significantly increased as a result of CoQ10 treatment.

CONCLUSION

CoQ10 reduced the neuronal damage caused by methadone in the hippocampus CA1.

Role of Coenzyme Q10 in Health and Disease: An Update on the Last 10 Years (2010-2020)

The present review focuses on preclinical and clinical studies conducted in the last decade that contribute to increasing knowledge on Coenzyme Q₁₀'s role in health and disease. Classical antioxidant and bioenergetic functions of the coenzyme have been taken into consideration, as well as novel mechanisms of action involving the redox-regulated activation of molecular pathways associated with anti-inflammatory activities. Cardiovascular research and fertility remain major fields of application of Coenzyme Q₁₀, although novel applications, in particular in relation to topical application, are gaining considerable interest. In this respect, bioavailability represents a major challenge and the innovation in formulation aspects is gaining critical importance.

Maternal high-fructose diet induced early-onset retinopathy via the suppression of synaptic plasticity mediated by mitochondrial dysfunction

Retinopathy is a leading cause of blindness, and there is currently no cure. Earlier identification of the progression of retinopathy could provide a better chance for intervention. Diet has profound effects on retinal function. A maternal high-fructose diet (HFD) triggers diseases in multiple organs. However, whether maternal HFD impairs retinal function in adult offspring is currently unknown. By using the rodent model of maternal HFD during pregnancy and lactation, our data indicated a reduced b-wave of electroretinography (ERG) in HFD female offspring at 3 mo of age compared with age-matched offspring of dams fed regular chow (ND). Immunofluorescence and Western blot analyses indicated that the distributions and expressions of synaptophysin, postsynaptic density protein 95 (PSD95), and phospho(p)-Ca²⁺/calmodulin-stimulated protein kinase IIα (CaMKIIα) were significantly suppressed in the HFD group. Furthermore, the ATP content and the mitochondrial respiratory protein, Mt CPX 4-2, were decreased. Moreover, the expressions of peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) and mitochondrial transcription factor A (TFAM) in the retina of the HFD group were downregulated. Treatment with coenzyme Q₁₀ (Q10), a key mediator of the electron transport chain, effectively reversed these abovementioned dysfunctions. Together, these results suggested that maternal HFD impaired retinal function in adult female offspring. The mechanism underlying early-onset retinopathy may involve the reduction in the capacity of mitochondrial energy production and the suppression of synaptic plasticity. Most importantly, mitochondria could be a feasible target to reprogram maternal HFD-damaged retinal function.NEW & NOTEWORTHY In this study, we provide novel evidence that maternal high-fructose diet during gestation and lactation could induce early-onset retinopathy in adult female offspring. Of note, the insufficient energy content, downregulated mitochondrial respiratory complex 4-2, and impaired mitochondrial biogenesis might contribute to the decrease of synaptic plasticity resulting in retinal function suppression. Oral application with coenzyme Q₁₀ for 4 wk could at least partially reverse the aforementioned molecular events and retinal function.

Adaptive responses to neurodegenerative stress in glaucoma

Glaucoma causes loss of vision through degeneration of the retinal ganglion cell (RGC) projection to the brain. The disease is characterized by sensitivity to intraocular pressure (IOP) conveyed at the optic nerve head, through which RGC axons pass unmyelinated to form the optic nerve. From this point, a pathogenic triumvirate comprising inflammatory, oxidative, and metabolic stress influence both proximal structures in the retina and distal structures in the optic projection. This review focuses on metabolic stress and how the optic projection may compensate through novel adaptive mechanisms to protect excitatory signaling to the brain. In the retina and proximal nerve head, the unmyelinated RGC axon segment is energy-inefficient, which leads to increased demand for adenosine-5'-triphosphate (ATP) at the risk of vulnerability to Ca²⁺-related metabolic and oxidative pressure. This vulnerability may underlie the bidirectional nature of progression. However, recent evidence highlights that the optic projection in glaucoma is not passive but rather demonstrates adaptive processes that may push back against neurodegeneration. In the retina, even as synaptic and dendritic pruning ensues, early progression involves enhanced excitability of RGCs. Enhancement involves depolarization of the resting membrane potential and increased response to light, independent of RGC morphological type. This response is axogenic, arising from increased levels and translocation of voltage-gated sodium channels (NaV) in the unmyelinated segment. During this same early period, large-scale networks of gap-junction coupled astrocytes redistribute metabolic resources to the optic projection stressed by elevated IOP to slow loss of axon function. This redistribution may reflect more local remodeling, as astrocyte processes respond to focal metabolic duress by boosting glycogen turnover in response to axonal activity in an effort to promote survival of the healthiest axons. Both enhanced excitability and metabolic redistribution are transient, indicating that the same adaptive mechanisms that apparently serve to slow progression ultimately may be too expensive for the system to sustain over longer periods.

Retinal proteomics of experimental glaucoma model reveal intraocular pressure-induced mediators of neurodegenerative changes

Current evidence suggests that exposure to chronically induced intraocular pressure (IOP) leads to neurodegenerative changes in the inner retina. This study aimed to determine retinal proteomic alterations in a rat model of glaucoma and compared findings with human retinal proteomics changes in glaucoma reported previously. We developed an experimental glaucoma rat model by subjecting the rats to increased IOP (9.3 ± 0.1 vs 20.8 ± 1.6 mm Hg) by weekly microbead injections into the eye (8 weeks). The retinal tissues were harvested from control and glaucomatous eyes and protein expression changes analysed using a multiplexed quantitative proteomics approach (TMT-MS3). Immunofluorescence was performed for selected protein markers for data validation. Our study identified 4304 proteins in the rat retinas. Out of these, 139 proteins were downregulated (≤0.83) while the expression of 109 proteins was upregulated (≥1.2-fold change) under glaucoma conditions (P ≤ .05). Computational analysis revealed reduced expression of proteins associated with glutathione metabolism, mitochondrial dysfunction/oxidative phosphorylation, cytoskeleton, and actin filament organisation, along with increased expression of proteins in coagulation cascade, apoptosis, oxidative stress, and RNA processing. Further functional network analysis highlighted the differential modulation of nuclear receptor signalling, cellular survival, protein synthesis, transport, and cellular assembly pathways. Alterations in crystallin family, glutathione metabolism, and mitochondrial dysfunction associated proteins shared similarities between the animal model of glaucoma and the human disease condition. In contrast, the activation of the classical complement pathway and upregulation of cholesterol transport proteins were exclusive to human glaucoma. These findings provide insights into the neurodegenerative mechanisms that are specifically affected in the retina in response to chronically elevated IOP.

Natural Products: Evidence for Neuroprotection to Be Exploited in Glaucoma

Glaucoma, a leading cause of irreversible blindness worldwide, is an optic neuropathy characterized by the progressive death of retinal ganglion cells (RGCs). Elevated intraocular pressure (IOP) is recognized as the main risk factor. Despite effective IOP-lowering therapies, the disease progresses in a significant number of patients. Therefore, alternative IOP-independent strategies aiming at halting or delaying RGC degeneration is the current therapeutic challenge for glaucoma management. Here, we review the literature on the neuroprotective activities, and the underlying mechanisms, of natural compounds and dietary supplements in experimental and clinical glaucoma.

Effect of Ubiquinol on Glaucomatous Neurodegeneration and Oxidative Stress: Studies for Retinal Ganglion Cell Survival and/or Visual Function

Oxidative stress is one of major causal factors in glaucomatous neurodegeneration. Ubiquinol promotes retinal ganglion cell (RGC) survival against glaucomatous insults such as oxidative stress. Here we investigated the effect of ubiquinol on RGC survival and/or visual function in mouse models of glaucoma and oxidative stress. DBA/2J and age-matched DBA/2J-Gpnmb+ (D2-Gpnmb+), which do not develop intraocular pressure elevation, or C57BL/6J mice were fed with ubiquinol (1%) or control diet daily for 5 or 2 months. We assessed RGC survival by Brn3a immunohistochemistry and measured expression levels of active and total BAX, peroxisome proliferator-activated receptor-gamma coactivator 1α, transcription factor A (TFAM) and oxidative phosphorylation (OXPHOS) complex protein. Following induction of oxidative stress by paraquat injection, we also assessed visual function. In glaucomatous retina, ubiquinol supplementation significantly promoted RGC survival, blocked BAX activation and increased TFAM and OXPHOS complex II protein expression. Also, ubiquinol supplementation ameliorated oxidative stress-induced visual dysfunction. These findings indicate that ubiquinol promotes RGC survival by increasing TFAM expression and OXPHOS complex II activity in glaucomatous neurodegeneration, and that ubiquinol enhances RGC survival and preserves visual function against oxidative stress. We propose that ubiquinol has a therapeutic potential for treating oxidative stress-associated glaucomatous neurodegeneration.

Effect of dietary modification and antioxidant supplementation on intraocular pressure and open-angle glaucoma

Primary open-angle glaucoma (POAG) is an age-dependent, intraocular pressure (IOP)-related degeneration of the retinal ganglion cells (RGC). At present, IOP is the only modifiable factor that has been identified to prevent glaucomatous vision loss. Though the pathogenesis of glaucomatous optic neuropathy is still not well understood, increasing evidence suggests oxidative stress may contribute to the induction and progression of glaucoma. Furthermore, antioxidant use may be protective against glaucoma through various mechanisms, including reducing IOP, preserving vascular health, and preventing ganglion cell loss. This article provides a comprehensive review of the effect of oxidative stress, diet, and antioxidant therapy on IOP and open-angle glaucoma.

Mitochondrial Markers in Aging and Primary Open-Angle Glaucoma

This review focuses on recent progress in understanding the role of mitochondrial markers in the context of mitochondrial dysfunction in glaucoma and discussing new therapeutic approaches to modulate mitochondrial function and potentially lead to improved outcomes in glaucoma.

AIBP protects retinal ganglion cells against neuroinflammation and mitochondrial dysfunction in glaucomatous neurodegeneration

Glaucoma is a leading cause of blindness worldwide in individuals 60 years of age and older. Despite its high prevalence, the factors contributing to glaucoma progression are currently not well characterized. Glia-driven neuroinflammation and mitochondrial dysfunction play critical roles in glaucomatous neurodegeneration. Here, we demonstrated that elevated intraocular pressure (IOP) significantly decreased apolipoprotein A-I binding protein (AIBP; gene name Apoa1bp) in retinal ganglion cells (RGCs), but resulted in upregulation of TLR4 and IL-1β expression in Müller glia endfeet. Apoa1bp^-/- mice had impaired visual function and Müller glia characterized by upregulated TLR4 activity, impaired mitochondrial network and function, increased oxidative stress and induced inflammatory responses. We also found that AIBP deficiency compromised mitochondrial network and function in RGCs and exacerbated RGC vulnerability to elevated IOP. Administration of recombinant AIBP prevented RGC death and inhibited inflammatory responses and cytokine production in Müller glia in vivo. These findings indicate that AIBP protects RGCs against glia-driven neuroinflammation and mitochondrial dysfunction in glaucomatous neurodegeneration and suggest that recombinant AIBP may be a potential therapeutic agent for glaucoma.

Combination Antioxidant/NSAID Therapies and Oral/Topical Ocular Delivery Modes for Prevention of Oxygen-Induced Retinopathy in a Rat Model

Given the complexity of oxygen-induced retinopathy (OIR), we tested the hypothesis that combination therapies and modes of administration would synergistically optimize efficacy for prevention of OIR. Newborn rats were exposed to neonatal intermittent hypoxia (IH) from the first day of life (P0) until P14 during which they received: (1) oral glutathione nanoparticles (nGSH) with topical ocular phosphate buffered saline (PBS); (2) nGSH with topical ocular Acuvail (ACV); (3) oral coenzyme Q10 (CoQ10) + ACV; (4) oral omega 3 polyunsaturated fatty acids (n-3 PUFAs) + ACV; (5) CoQ10 + n-3 PUFAs + PBS; or (6) CoQ10 + n-3 PUFAs + ACV. Treated groups raised in room air (RA) served as controls. At P14, pups were placed in RA with no treatment until P21. Retinal vascular pathology, ocular angiogenesis biomarkers, histopathology, and morphometry were determined. All combination treatments in IH resulted in the most beneficial retinal outcomes consistent with suppression of angiogenesis growth factors during reoxygenation/reperfusion and no significant adverse effects on somatic growth. nGSH + PBS also reversed IH-induced retinopathy, but had negative effects on growth. Simultaneously targeting oxidants, inflammation, and poor growth mitigates the damaging effects of neonatal IH on the developing retina. Therapeutic synergy with combination delivery methods enhance individual attributes and simultaneously target multiple pathways involved in complex diseases such as OIR.

The interplay between oxidative stress and bioenergetic failure in neuropsychiatric illnesses: can we explain it and can we treat it?

Nitro-oxidative stress and lowered antioxidant defences play a key role in neuropsychiatric disorders such as major depression, bipolar disorder and schizophrenia. The first part of this paper details mitochondrial antioxidant mechanisms and their importance in reactive oxygen species (ROS) detoxification, including details of NO networks, the roles of H₂O₂ and the thioredoxin/peroxiredoxin system, and the relationship between mitochondrial respiration and NADPH production. The second part highlights and identifies the causes of the multiple pathological sequelae arising from self-amplifying increases in mitochondrial ROS production and bioenergetic failure. Particular attention is paid to NAD⁺ depletion as a core cause of pathology; detrimental effects of raised ROS and reactive nitrogen species on ATP and NADPH generation; detrimental effects of oxidative and nitrosative stress on the glutathione and thioredoxin systems; and the NAD⁺-induced signalling cascade, including the roles of SIRT1, SIRT3, PGC-1α, the FOXO family of transcription factors, Nrf1 and Nrf2. The third part discusses proposed therapeutic interventions aimed at mitigating such pathology, including the use of the NAD⁺ precursors nicotinamide mononucleotide and nicotinamide riboside, both of which rapidly elevate levels of NAD⁺ in the brain and periphery following oral administration; coenzyme Q₁₀ which, when given with the aim of improving mitochondrial function and reducing nitro-oxidative stress in the brain, may be administered via the use of mitoquinone, which is in essence ubiquinone with an attached triphenylphosphonium cation; and N-acetylcysteine, which is associated with improved mitochondrial function in the brain and produces significant decreases in oxidative and nitrosative stress in a dose-dependent manner.

The Use of Vitamins and Coenzyme Q10 for the Treatment of Vascular Occlusion Diseases Affecting the Retina

Nutritional supplementation with antioxidants and vitamins is widely recommended in the treatment of vascular disorders affecting the retina, although there is insufficient evidence on its effectiveness. The vitamin-like compound coenzyme Q10 (CoQ10) is a nutritional supplement of current interest to treat neurodegenerative diseases. Here, we report a retrospective clinical case series study of 48 patients diagnosed with retinal vascular diseases, including non-arteritic ischemic optic neuropathy (NAION), retinal artery occlusion (RAO), and homonymous hemianopia or quadrantanopia following stroke, treated with oral supplementation with CoQ10 (100 mg per day) and vitamins. Patient follow-up was performed using the Humphrey field analyzer and 30-2 testing algorithm to determine the visual field index (VFI) and progression rates. All treated patients showed positive VFI progression rates per year: +11.5 ± 15% for NAION patients (n = 18), +22 ± 17% for RAO patients (n = 7), +9.3 ± 10.5% for hemianopia/quadrantanopia patients (n = 10), and +11 ± 21% for patients with other conditions (n = 13). The interruption of CoQ10 supplementation in one patient resulted in a pronounced decrease of the VFI, which was partially recovered when treatment was restored. This study supports the role of CoQ10 as a nutritional therapeutic agent for vascular diseases affecting the retina. Owing to decreased VFI after interruption of CoQ10, its beneficial effects may be reversible.

Contrary effects of coenzyme Q10 and vitamin E after testicular ischemia/reperfusion in a rat model validated with glucose metabolism imaging

OBJECTIVE

To evaluate the efficacy of antioxidants in cellular-level post-ischemia/reperfusion injury of the testis and to validate these effects with ¹⁸F-fluorodeoxyglucose positron emission tomography.

METHODS

Fifty-six adult male rats were randomly divided into seven groups-Group 1: sham; Group 2: ischemia/reperfusion only group; Group 3: ischemia was induced and vitamin E (100 mg/kg) was administered intraperitoneally 30 min before reperfusion; Group 4: vitamin E was given intraperitoneally without ischemia/reperfusion; Group 5: ischemia was induced and coenzyme Q10 (10 mg/body weight) was administered intraperitoneally 30 min before reperfusion; Group 6: coenzyme Q10 was administered intraperitoneally without ischemia/reperfusion; Group 7: ischemia was induced and coenzyme Q10 + vitamin E was administered intraperitoneally 30 min before reperfusion. After detorsion, fluorodeoxyglucose was applied to all groups according to the animals' weight and fluorodeoxyglucose positron emission tomography was performed after 1 h. In pursuit of imaging, orchiectomy was performed for histopathological and biochemical evaluations.

RESULTS

A significant effect of group on catalase, maximum standardized uptake value, and seminiferous tubule diameters (p < 0.005) was observed. According to this, combining ischemia/reperfusion with vitamin E increased the maximum standardized uptake value significantly higher than in all other groups; in addition, catalase was significantly higher than in Groups 4-6. Histopathological outcomes revealed that "sham" had significantly larger seminiferous tubule diameter than Groups 2-4. Also, "ischemia/reperfusion" was the only group which had significantly smaller seminiferous tubule diameters than Groups 6 and 7.

CONCLUSION

In contrast to vitamin E, coenzyme Q10 provided remarkable regression of oxidative stress-induced enzymes and revealed consistent effects on histopathological outcomes, which were validated with fluorodeoxyglucose positron emission tomography imaging.

Coenzyme Q10 suppresses oxidative stress and apoptosis via activating the Nrf-2/NQO-1 and NF-κB signaling pathway after spinal cord injury in rats

Spinal cord injury (SCI) is one of the most devastating diseases that may cause paralysis, disability and irreversible loss of functions, which ultimately lead to permanent disabilities and a decrease in patient life expectancy. Coenzyme Q10 (CoQ10) is a lipid-soluble vitamin-like benzoquinone compound that can exert antioxidant and anti-apoptotic functions in a variety of diseases. However, the antioxidant and anti-apoptotic effects of CoQ10 in the treatment of SCI are still unknown. Therefore, we designed experiments to measure the changes in antioxidant capacity (glutathione (GSH), superoxide dismutase (SOD) and the end product of lipid peroxidation (MDA)) and apoptosis products (Bax, Bcl-2 and Caspase-3) to evaluate the protective effects of CoQ10 on SCI and investigated whether CoQ10 exerts its functions through the Nrf-2/NQO-1 and NF-κB signaling pathway. Our results showed that CoQ10 treatment could significantly decrease the levels of oxidative products (MDA) and increase the activities of antioxidant enzymes (SOD and GSH) against oxidative stress, as well as decrease the levels of pro-apoptotic proteins (Bax and Caspase-3) and increase the levels of anti-apoptotic proteins (Bcl-2) against apoptosis after SCI. We also observed that CoQ10 exerted beneficial effects through the Nrf-2/NQO-1 and NF-κB signaling pathway. These findings suggested that CoQ10 had a protective effect by decreasing oxidative stress and apoptosis after SCI. Thus, our data may provide a new approach wherein CoQ10 may be considered as a potential effective therapeutic for the treatment of SCI.

Neuroprotective effects of topical coenzyme Q10 + vitamin E in mechanic optic nerve injury model

PURPOSE

We aimed to create mechanic optic nerve injury model in rats and investigate the neuroprotective effects of topical Coenzyme Q10 + Vitamin E (CoQ + Vit.E) molecules on retinal ganglion cells.

METHODS

Mechanic optic nerve injury model was created in the right eyes of rats (n = 12). Rats were divided into two groups: glaucoma model with sham treatment and topical CoQ + Vit.E treatment. Treatment was applied for 4 weeks. Glial fibrillary acidic protein, Brn-3a antibody, and anti-Iba1 were examined by immunohistochemistry. Glial fibrillary acidic protein, Bax, Bcl-xL, and Tfam protein expression were measured by Western blot analysis.

RESULTS

The number of Brn-3a-positive retinal ganglion cell was 15.0 ± 1.0 (min: 14, max: 16) in sham treatment group and 22.2 ± 4.8 (min: 18, max: 29) in topical CoQ10 + Vit.E treatment group. The protection of Brn-3a in CoQ10 + Vit.E was statistically significant (p < 0.05). Glial fibrillary acidic protein-positive astroglial counts were recorded as 11.7 ± 2.1 (min: 10, max: 14) in sham treatment and 2.5 ± 1.5 (min: 1, max: 4) in topical CoQ10 + Vit.E treatment group (p < 0.05). Topical CoQ10 + Vit.E treatment also decreased Iba1 expression in the retina of mechanic optic nerve injury groups. CoQ10 + Vit.E treatment prevented apoptotic cell death by increasing Bcl-xL protein expression. Also, CoQ10 + Vit.E preserved Tfam protein expression in the retina.

CONCLUSION

This study has shown that in glaucoma treatment the neuron protecting effect of topical CoQ10 + Vit.E molecules can be valuable.

Bioavailability and Sustained Plasma Concentrations of CoQ10 in Healthy Volunteers by a Novel Oral Timed-Release Preparation

Coenzyme Q10 (CoQ10) is a natural compound with potent antioxidant properties. Its provision through diet does not always allow adequate levels in the human body, and supplementation is often necessary. This bioavailability study intended to explore the plasma concentration levels of a novel CoQ10 oral preparation (COQUN^®, Coenzyme Q10 Miniactives Retard 100 mg capsules) mimicking assumption on a regular basis. Twenty-four healthy adults tested a single dose of CoQ10 100 mg in one day to assess bioavailability. After a one week wash-out period, they were randomly assigned (1:1) to continuous administration for four weeks: Group A (n = 12) 100 mg once a day (OD); and Group B (n = 12) 100 mg twice a day (BID). During the single dose phase, C_max was observed at 4 h, and the mean values of AUC_t and T_max were 8754 μg/mL·h and 4.29 h, respectively. The multiple dose phase showed increasing plasma levels up to 7 days after the start of administration, and sustained high concentrations during the all administration period. No relevant adverse events were reported. These results show that Miniactives^® technology can release CoQ10 to allow high constant blood concentrations without a sharp decrease. This may be the first step of evidence for a potential new antioxidative treatment in human chronic diseases deserving high CoQ10 levels.

Coenzyme Q10 treatment improved visual field after homonymous quadrantanopia caused by occipital lobe infarction

Purpose

To report the clinical findings and management of a case of occipital lobe infarction with homonymous quadrantanopia in a patient treated with vitamins and coenzyme Q10.

Observations

A currently 69-years-old patient presenting in 2007 left inferior quadrantanopia following a right occipital lobe stroke with initial visual field index of 82% and 79% in the right and left eyes, respectively. From 2007 to 2010 was treated with vitamin and antioxidant complexes, without specific signs of changes observed in the visual field (81% right eye, 79% left eye). In 2011 was treated for the first time with coenzyme Q10 (Active complex^® Q10 Gold 100 mg) in addition to the vitamin and antioxidant supplementation. A promptly slight improvement of the visual field in both eyes was observed. In 2013, a remarkable improvement was noticed observing a slight scotoma where previously presented the quadrantanopia. Thereafter, in the successive one-year follow-up examinations the patient experienced an exponential improvement in the visual field with gradually fading of the scotoma. Currently the patient no longer presents any sign of quadrantanopia, with normal visual field in both eyes (99% right eye, 98% left eye).

Conclusion and importance

Spontaneous improvement more than 6 months after stroke is thought to be unlikely. However, we observed, for the first time, an amelioration of the visual field after 10 years of an occipital lobe stroke. The combination of vitamins and coenzyme Q10 (100 mg) improved the prognosis with significant recovery of the visual field, which is impossible to recover under current knowledge.

Comparative Effects of Coenzyme Q10 or n-3 Polyunsaturated Fatty Acid Supplementation on Retinal Angiogenesis in a Rat Model of Oxygen-Induced Retinopathy

Neonatal intermittent hypoxia (IH) or apnea afflicts 70% to 90% of all preterm infants <28 weeks gestation, and is associated with severe retinopathy of prematurity (ROP). We tested the hypotheses that coenzyme Q10 (CoQ10) or omega-3 polyunsaturated fatty acids (n-3 PUFAs) supplementation during neonatal IH reduces the severity of oxygen-induced retinopathy (OIR). Newborn rats were exposed to two IH paradigms: (1) 50% O₂ with brief hypoxia (12% O₂); or (2) 21% O₂ with brief hypoxia, until postnatal day 14 (P14), during which they received daily oral CoQ10 in olive oil, n-3 PUFAs in fish oil, or olive oil only and compared to room air (RA) treated groups. Pups were examined at P14, or placed in RA until P21. Retinal angiogenesis, histopathology, and morphometry were determined. Both IH paradigms produced severe OIR, but these were worsened with 50/12% O₂ IH. CoQ10 and n-3 PUFAs reduced the severity of OIR, as well as ocular growth factors in both IH paradigms, but CoQ10 was more effective in 50/12% O₂ IH. Supplementation with either CoQ10 or n-3 PUFAs targeting IH-induced retinal injury is individually effective for ameliorating specific characteristics consistent with ROP. Given the complexity of ROP, further studies are needed to determine whether combined CoQ10 and n-3 PUFAs supplementation would optimize their efficacy and result in a better outcome.

Molecular mechanisms of neuroprotective effect of adjuvant therapy with phenytoin in pentylenetetrazole-induced seizures: Impact on Sirt1/NRF2 signaling pathways

Current anticonvulsant therapies are principally aimed at suppressing neuronal hyperexcitability to prevent or control the incidence of seizures. However, the role of oxidative stress processes in seizures led to the proposition that antioxidant compounds may be considered as promising candidates for limiting the progression of epilepsy. Accordingly, the aim of this study is to determine if coenzyme Q10 (CoQ10) and alpha-tocopherol (α-Toc) have a neuroprotective effect in rats against the observed oxidative stress and inflammation during seizures induced by pentylenetetrazole (PTZ) in rats, and to study their interactions with the conventional antiseizure drug phenytoin (PHT), either alone or in combination. Overall, the data revealed that α-Toc and CoQ10 supplementation can ameliorate PTZ-induced seizures and recommended that nuclear factor erythroid 2-related factor 2 (NRF2) and silencing information regulator 1 (Sirt1) signaling pathways may exemplify strategic molecular targets for seizure therapies. The results of the present study provide novel mechanistic insights regarding the protective effects of antioxidants and suggest an efficient therapeutic strategy to attenuate seizures. Additionally, concurrent supplementation of CoQ10 and α-Toc may be more effective than either antioxidant alone in decreasing inflammation and oxidative stress in both cortical and hippocampal tissues. Also, CoQ10 and α-Toc effectively reverse the PHT-mediated alterations in the brain antioxidant status when compared to PHT only.

Down-regulated miR-187 promotes oxidative stress-induced retinal cell apoptosis through P2X7 receptor

Several microRNAs (miRNAs) expressed in the retina were confirmed to involve in retinal cell apoptosis, which was closely linked with the development of retinal diseases. Our previous studies have confirmed a vital role of miR-187 in retinal cells apoptosis. The aim of this study was to further elucidate the precise role of miR-187 and its probable mechanisms in RGC-5 cells apoptosis. The cellular oxidative stress status was assessed by reactive oxygen species (ROS) production and malondialdehyde (MDA) level. Our results showed that the elevated pressure, glutamate and H₂O₂-induced oxidative stress in RGC-5 cells was accompanied by a decrease in miR-187 expression and an increase in P2X7R expression. However, overexpression of miR-187 reversed this activation of oxidative stress in RGC-5 cells. Moreover, we also revealed that miR-187 inhibited the oxidative stress-induced apoptosis of RGC-5 cells through negative regulating P2X7R, probably through interacting with the 3'UTR of P2X7R. Finally, we confirmed that the forced miR-187 expression alleviated oxidative stress injury in retina tissues of rat models with chronic ocular hypertension. Our data demonstrated that miR-187/P2X7R signaling was involved in retinal cell apoptosis, at least in part, through activating oxidative stress.

Ubiquinol promotes retinal ganglion cell survival and blocks the apoptotic pathway in ischemic retinal degeneration

Coenzyme Q10 (CoQ₁₀) protects retinal ganglion cells (RGCs) in experimental retinal ischemia and glaucoma by scavenging reactive oxygen species. We tested whether a diet supplemented with ubiquinol, the reduced form of CoQ₁₀, promotes RGC survival and blocks the apoptotic pathway in ischemic mouse retina induced by acute high intraocular pressure (IOP) elevation. Ubiquinol (1%) treatment significantly promoted RGC survival at 2 weeks after ischemia/reperfusion. The ubiquinol treatment significantly blocked activation of astroglial and microglial cells in the ischemic retina at 2 weeks. While the ubiquinol treatment significantly decreased active Bax protein expression in the ischemic retina, phosphorylation of Bad at serine 112 and Bcl-xL protein expression were preserved in the ubiquinol-treated ischemic retina at 12 h. Consistently, the ubiquinol treatment prevented apoptotic cell death by blocking caspase-3 cleavage. These results suggest that the ubiquinol enhances RGC survival by modulating the Bax/Bad/Bcl-xL-mediated apoptotic pathway in the ischemic retina. Ubiquinol has therapeutic potential for ameliorating elevated IOP-induced ischemic retinal degeneration.

Limb remote ischemic conditioning of the recipient protects the liver in a rat model of arterialized orthotopic liver transplantation

Background

Ischemic-reperfusion (IR) injury still represents a major concern in clinical transplantation, especially in the era of extreme organ shortage and extended criteria donor organs. In the present study we aimed to investigate the hepatoprotective effects of remote ischemic conditioning (RIC) in a rat model of arterialized orthotopic liver transplantation (OLT).

Methods

Male Lewis rats were used (n = 144 / 72 OLT cases; 240–340g) as donors and recipients. Livers were flushed and stored in 4°C HTK-solution for 8h before implantation. Recipients were randomly allocated into three experimental groups: RIC 1, RIC 2, Control. In RIC 1, RIC 2 groups, RIC was applied in the recipient before hepatectomy or after reperfusion (4x5-5min IR via clamping the infrarenal aorta), respectively. Animals were sacrificed at 1, 3, 24, 168h post-reperfusion (n = 6 recipient/group/time point). Hepatocellular injury, graft circulation, serum cytokines, tissue redox-stress and adenosine-triphosphate (ATP) levels have been assessed. Additional markers were analyzed, using Western blotting and reverse-transcription polymerase chain reaction.

Results

RIC 1 group showed significantly (p<0.05) improved portal venous and microcirculation flow as well as velocity. RIC has significantly reduced tissue injury according to the serum levels of transaminases and results of histopathological evaluation. Reduced TUNEL-staining (p<0.01 RIC 1–2 vs. Control) and elevated pBAD/BAD ratio was detected in the RIC groups (p<0.01 RIC 1 vs. Control). Supporting findings were obtained from measurements of serum IL-10 as well as tissue malondialdehyde and ATP levels. Hemoxygenase-1 (HO-1) mRNA-expression was significantly higher in RIC 1 compared to Control (p<0.05 RIC 1 vs. Control).

Conclusion

These results suggest that RIC might confer potent protection against the detrimental effects of IR injury including tissue damage, apoptosis, graft circulation, inflammation, tissue energetic status in OLT. HO-1 overexpression might play an orchestrating role in RIC mediated organ protection. An earlier intervention (RIC 1 protocol) was more effective than remote conditioning after graft reperfusion.

Neuroprotective agents in the management of glaucoma

Glaucoma is an optic neuropathy, specifically a neurodegenerative disease characterized by loss of retinal ganglion cells (RGCs) and their axons. The pathogenesis of RGC loss in glaucoma remains incompletely understood and a broad range of possible mechanisms have been implicated. Clinical evidence indicates that lowering intraocular pressure (IOP) does not prevent progression in all patients; therefore, risk factors other than those related to IOP are involved in the disease. The need for alternative, non-IOP-lowering treatments focused at preventing progression, that is, neuroprotectants, has become of interest to both the patient and the physician. Experimental evidence accumulated during the past two decades lend a great deal of support to molecules endowed with neuroprotective features. However, translation to the clinic of the latter drugs results unsuccessful mostly because of the lack of reliable in vivo measure of retinal damage, thus hampering the good therapeutic potential of neuroprotective agents given alone or as adjuvant therapy to IOP-lowering agents. Further research effort is needed to better understand the mechanisms involved in glaucoma and the means to translate into clinic neuroprotective drugs.

Co-Enzyme Q10 and n-3 Polyunsaturated Fatty Acid Supplementation Reverse Intermittent Hypoxia-Induced Growth Restriction and Improved Antioxidant Profiles in Neonatal Rats

Neonatal intermittent hypoxia (IH) increases the risk for many morbidities in extremely low birth weight/gestational age (ELBW/ELGA) neonates with compromised antioxidant systems and poor growth. We hypothesized that supplementation with coenzyme Q10 (CoQ10, ubiquinol) or n-3 polyunsaturated fatty acids (PUFAs) during neonatal IH improves antioxidant profiles and somatic growth in neonatal rats. Newborn rats were exposed to two IH paradigms at birth (P0): (1) 50% O₂ with brief hypoxic episodes (12% O₂); or (2) room air (RA) with brief hypoxia, until P14 during which they received daily oral CoQ10 in olive oil, n-3 PUFAs in fish oil, or olive oil only from P0 to P14. Pups were studied at P14 or placed in RA until P21 for recovery from IH (IHR). Body weight and length; organ weights; and serum antioxidants and growth factors were determined at P14 and P21. Neonatal IH resulted in sustained reductions in somatic growth, an effect that was reversed with n-3 PUFAs. Improved growth was associated with higher serum growth factors. CoQ10 decreased superoxide dismutase (SOD) and glutathione, but increased catalase, suggesting reduced oxidative stress. Further studies are needed to determine the synergistic effects of CoQ10 and n-3 PUFA co-administration for the prevention of IH-induced oxidative stress and postnatal growth deficits.

CoQ10 Augments Rosuvastatin Neuroprotective Effect in a Model of Global Ischemia via Inhibition of NF-κB/JNK3/Bax and Activation of Akt/FOXO3A/Bim Cues

Statins were reported to lower the Coenzyme Q10 (CoQ10) content upon their inhibition of HMG-CoA reductase enzyme and both are known to possess neuroprotective potentials; therefore, the aim is to assess the possible use of CoQ10 as an adds-on therapy to rosuvastatin to improve its effect using global I/R model. Rats were allocated into sham, I/R, rosuvastatin (10 mg/kg), CoQ10 (10 mg/kg) and their combination. Drugs were administered orally for 7 days before I/R. Pretreatment with rosuvastatin and/or CoQ10 inhibited the hippocampal content of malondialdehyde, nitric oxide, and boosted glutathione and superoxide dismutase. They also opposed the upregulation of gp91^phox, and p47^phox subunits of NADPH oxidase. Meanwhile, both agents reduced content/expression of TNF-α, iNOS, NF-κBp65, ICAM-1, and MPO. Besides, all regimens abated cytochrome c, caspase-3 and Bax, but increased Bcl-2 in favor of cell survival. On the molecular level, they increased p-Akt and its downstream target p-FOXO3A, with the inhibition of the nuclear content of FOXO3A to downregulate the expression of Bim, a pro-apoptotic gene. Additionally, both treatments downregulate the JNK3/c-Jun signaling pathway. The effect of the combination regimen overrides that of either treatment alone. These effects were reflected on the alleviation of the hippocampal damage in CA1 region inflicted by I/R. Together, these findings accentuate the neuroprotective potentials of both treatments against global I/R by virtue of their rigorous multi-pronged actions, including suppression of hippocampal oxidative stress, inflammation, and apoptosis with the involvement of the Akt/FOXO3A/Bim and JNK3/c-Jun/Bax signaling pathways. The study also nominates CoQ10 as an adds-on therapy with statins.

Targets of Neuroprotection in Glaucoma

Progressive neurodegeneration of the optic nerve and the loss of retinal ganglion cells is a hallmark of glaucoma, the leading cause of irreversible blindness worldwide, with primary open-angle glaucoma (POAG) being the most frequent form of glaucoma in the Western world. While some genetic mutations have been identified for some glaucomas, those associated with POAG are limited and for most POAG patients, the etiology is still unclear. Unfortunately, treatment of this neurodegenerative disease and other retinal degenerative diseases is lacking. For POAG, most of the treatments focus on reducing aqueous humor formation, enhancing uveoscleral or conventional outflow, or lowering intraocular pressure through surgical means. These efforts, in some cases, do not always lead to a prevention of vision loss and therefore other strategies are needed to reduce or reverse the progressive neurodegeneration. In this review, we will highlight some of the ocular pharmacological approaches that are being tested to reduce neurodegeneration and provide some form of neuroprotection.

Hydrogen Sulphide modulating mitochondrial morphology to promote mitophagy in endothelial cells under high-glucose and high-palmitate

Endothelial cell dysfunction is one of the main reasons for type II diabetes vascular complications. Hydrogen sulphide (H₂S) has antioxidative effect, but its regulation on mitochondrial dynamics and mitophagy in aortic endothelial cells under hyperglycaemia and hyperlipidaemia is unclear. Rat aortic endothelial cells (RAECs) were treated with 40 mM glucose and 200 μM palmitate to imitate endothelium under hyperglycaemia and hyperlipidaemia, and 100 μM NaHS was used as an exogenous H₂S donor. Firstly, we demonstrated that high glucose and palmitate decreased H₂S production and CSE expression in RAECs. Then, the antioxidative effect of H₂S was proved in RAECs under high glucose and palmitate to reduce mitochondrial ROS level. We also showed that exogenous H₂S inhibited mitochondrial apoptosis in RAECs under high glucose and palmitate. Using Mito Tracker and transmission electron microscopy assay, we revealed that exogenous H₂S decreased mitochondrial fragments and significantly reduced the expression of p‐Drp‐1/Drp‐1 and Fis1 compared to high‐glucose and high‐palmitate group, whereas it increased mitophagy by transmission electron microscopy assay. We demonstrated that exogenous H₂S facilitated Parkin recruited by PINK1 by immunoprecipitation and immunostaining assays and then ubiquitylated mitofusin 2 (Mfn2), which illuminated the mechanism of exogenous H₂S on mitophagy. Parkin siRNA suppressed the expression of Mfn2, Nix and LC3B, which revealed that it eliminated mitophagy. In summary, exogenous H₂S could protect RAECs against apoptosis under high glucose and palmitate by suppressing oxidative stress, decreasing mitochondrial fragments and promoting mitophagy. Based on these results, we proposed a new mechanism of H₂S on protecting endothelium, which might provide a new strategy for type II diabetes vascular complication.