Nattokinase Attenuates Retinal Neovascularization Via Modulation of Nrf2/HO-1 and Glial Activation

Melatonin Improves Oxidative Stress Injury in Retinopathy of Prematurity by Targeting miR-23a-3p/Nrf2

PURPOSE

Melatonin has promising protective effects for retinopathy. However, its roles in retinopathy of prematurity (ROP) and the underlying mechanisms remain unknown. We aimed to explore its roles and mechanisms in a ROP model.

METHODS

Hematoxylin and eosin staining were used to observe the morphology of the retina. Immunofluorescence was used to detect positive (Nrf2+ and VEGF+) cells. Immunohistochemistry was used to detect the level of nuclear expression of PCNA in retinal tissue. Transmission electron microscope (TEM) was used to observe the morphology and structure of pigment cells. qRT-PCR was used to assay the expression of miR-23a-3p, Nrf2, and HO-1. Western blotting was used to detect the expression of Nrf2, HO-1, β-actin, and Lamin B1.

RESULTS

Melatonin or miR-23a-3p antagomir treatment could ameliorate the Oxygen-induced pathological changes, increased the expression of Nrf2 and HO-1, SOD, and GSH-Px, and decreased the expression of VEGF, miR-23a-3p, MDA and the apoptosis in the ROP model. Further target prediction and luciferase reporter assays confirmed the targeted binding relationship between miR-23a-3p and Nrf2.

CONCLUSION

Our study showed that melatonin could ameliorate H2O2-induced apoptosis and oxidative stress injury in RGC cells by mediating miR-23a-3p/Nrf2 signaling pathway, thereby improving retinal degeneration.

Molecular hydrogen promotes retinal vascular regeneration and attenuates neovascularization and neuroglial dysfunction in oxygen-induced retinopathy mice

BACKGROUND

Retinopathy of Prematurity (ROP) is a proliferative retinal vascular disease occurring in the retina of premature infants and is the main cause of childhood blindness. Nowadays anti-VEGF and retinal photocoagulation are mainstream treatments for ROP, but they develop a variety of complications. Hydrogen (H2) is widely considered as a useful neuroprotective and antioxidative therapeutic method for hypoxic-ischemic disease without toxic effects. However, whether H2 provides physiological angiogenesis promotion, neovascularization suppression and glial protection in the progression of ROP is largely unknown.This study aims to investigate the effects of H2 on retinal angiogenesis, neovascularization and neuroglial dysfunction in the retinas of oxygen-induced retinopathy (OIR) mice.

METHODS

In this study, mice that were seven days old and either wild-type (WT) or Nrf2-deficient (Nrf2-/-) were exposed to 75% oxygen for 5 days and then returned to normal air conditions. Different stages of hydrogen gas (H2) inhalation were administered. Vascular obliteration, neovascularization, and blood vessel leakage were analyzed and compared. To count the number of neovascularization endothelial nuclei, routine HE staining of retinal sections was conducted. Immunohistochemistry was performed using DyLight 594 labeled GSL I-isolectin B4 (IB4), as well as primary antibodies against proliferating cell nuclear antigen (PCNA), glial fibrillary acidic protein (GFAP), and Iba-1. Western blots were used to measure the expression of NF-E2-related factor 2 (Nrf2), vascular endothelial growth factor (VEGF), Notch1, Dll4, and HIF-1α. Additionally, the expression of target genes such as NQO1, HO-1, Notch1, Hey1, Hey2, and Dll4 was measured. Human umbilical vein endothelial cells (HUVECs) treated with H2 under hypoxia were used as an in vitro model. RT-PCR was used to evaluate the mRNA expression of Nrf2, Notch/Dll4, and the target genes. The expression of reactive oxygen species (ROS) was observed using immunofluorescence staining.

RESULTS

Our results indicate that 3-4% H2 does not disturb retinal physiological angiogenesis, but ameliorates vaso-obliteration and neovascularization in OIR mice. Moreover, H2 prevents the decreased density and reverses the morphologic and functional changes in retinal astrocytes caused by oxygen-induced injury. In addition, H2 inhalation reduces microglial activation, especially in the area of neovascularization in OIR mice. H2 plays a protective role in vascular regeneration by promoting Nrf2 activation and suppressing the Dll4-induced Notch signaling pathway in vivo. Also, H2 promotes the proliferation of HUVECs under hypoxia by negatively regulating the Dll4/Notch pathway and reducing ROS levels through Nrf2 pathway aligning with our findings in vivo.Moreover, the retinal oxygen-sensing mechanisms (HIF-1α/VEGF) are also involved in hydrogen-mediated retinal revascularization and neovascularization suppression.

CONCLUSIONS

Collectively, our results indicate that H2 could be a promising therapeutic agent for POR treatment and that its beneficial effect in human ROP might involve the activation of the Nrf2-Notch axis as well as HIF-1α/VEGF pathways.

The significance of precisely regulating heme oxygenase-1 expression: Another avenue for treating age-related ocular disease?

Aging entails the deterioration of the body's organs, including overall damages at both the genetic and cellular levels. The prevalence of age-related ocular disease such as macular degeneration, dry eye diseases, glaucoma and cataracts is increasing as the world's population ages, imposing a considerable economic burden on individuals and society. The development of age-related ocular disease is predominantly triggered by oxidative stress and chronic inflammatory reaction. Heme oxygenase-1 (HO-1) is a crucial antioxidant that mediates the degradative process of endogenous iron protoporphyrin heme. It catalyzes the rate-limiting step of the heme degradation reaction, and releases the metabolites such as carbon monoxide (CO), ferrous, and biliverdin (BV). The potent scavenging activity of these metabolites can help to defend against peroxides, peroxynitrite, hydroxyl, and superoxide radicals. Other than directly decomposing endogenous oxidizing substances (hemoglobin), HO-1 is also a critical regulator of inflammatory cells and tissue damage, exerting its anti-inflammation activity through regulating complex inflammatory networks. Therefore, promoting HO-1 expression may act as a promising therapeutic strategy for the age-related ocular disease. However, emerging evidences suggest that the overexpression of HO-1 significantly contributes to ferroptosis due to its dual nature. Surplus HO-1 leads to excessive Fe2+ and reactive oxygen species, thereby causing lipid peroxidation and ferroptosis. In this review, we elucidate the role of HO-1 in countering age-related disease, and summarize recent pharmacological trials that targeting HO-1 for disease management. Further refinements of the knowledge would position HO-1 as a novel therapeutic target for age-related ocular disease.

Nattokinase attenuates endothelial inflammation through the activation of SRF and THBS1

Natto contains a potent fibrinolytic enzyme called nattokinase (NK), which has thrombolytic, antihypertensive, antiatherosclerotic and lipid-lowering effects. Although NK has been recognized for its beneficial effect on humans with atherosclerotic cardiovascular disease (ASCVD), the underlying mechanisms involved in vascular inflammation-atherosclerosis development remain largely unknown. The current study aimed to explore the effects of NK on gene regulation, autophagy, necroptosis and inflammasome in vascular inflammation. The transcriptional profiles of NK in endothelial cells (ECs) by RNA sequencing (RNA-seq) revealed that NK affected THBS1, SRF and SREBF1 mRNA expression. In Q-PCR analysis, SRF and THBS1 were upregulated but SREBF1 was unaffected in ECs treated with NK. NK treatment induced autophagy and inhibited NLRP3 inflammasome and necroptosis in ECs. Furthermore, the inhibition of SRF or THBS1 by siRNA suppressed autophagy and enhanced the NLRP3 inflammasome and necroptosis. In a mouse model, NK reduced vascular inflammation by activating autophagy and inhibiting NLRP3 inflammasome and necroptosis. Our findings provide the first evidence that NK upregulates SRF and THBS1 genes, subsequently increasing autophagy and decreasing necroptosis and NLRP3 inflammasome formation to reduce vascular inflammation. Therefore, NK could serve as nutraceuticals or adjuvant therapies to reduce vascular inflammation and possible atherosclerosis progression.

Protective effects of nattokinase against microvasculopathy and neuroinflammation in diabetic retinopathy

AIMS

Diabetic retinopathy (DR) is a significant global public health concern. Alternative, safe, and cost-effective pharmacologic approaches are warranted. We aimed to investigate the therapeutic potential of nattokinase (NK) for early DR and the underlying molecular mechanism.

METHODS

A mouse model of diabetes induced by streptozotocin was utilized and NK was administered via intravitreal injection. Microvascular abnormities were evaluated by examining the leakage from blood-retinal barrier dysfunction and loss of pericytes. Retinal neuroinflammation was examined through the assessment of glial activation and leukostasis. The level of high mobility group box 1 (HMGB1) and its downstream signaling molecules was evaluated following NK treatment.

RESULTS

NK administration significantly improved the blood-retinal barrier function and rescued pericyte loss in the diabetic retinas. Additionally, NK treatment inhibited diabetes-induced gliosis and inflammatory response and protected retinal neurons from diabetes-induced injury. NK also improved high glucose-induced dysfunction in cultured human retinal micrangium endothelial cells. Mechanistically, NK regulated diabetes-induced inflammation partially by modulating HMGB1 signaling in the activated microglia.

CONCLUSIONS

This study demonstrated the protective effects of NK against microvascular damages and neuroinflammation in the streptozotocin-induced DR model, suggesting that NK could be a potential pharmaceutical agent for the treatment of DR.

Development of Novel Monoclonal Antibodies Against Nattokinase

Nattokinase is a protease produced by Bacillus subtilis var. natto that exhibits various beneficial biological effects. Thus, a reliable assay to determine nattokinase levels is needed. In this study, we developed novel mouse monoclonal antibodies (mAbs) that recognize nattokinase, and created a specific and sensitive enzyme-linked immunosorbent assay (ELISA) to measure nattokinase levels. The ELISA was developed using a combination of new mouse antinattokinase mAbs used as capture antibodies coated onto 96-well plates, with a peroxidase-conjugated antibody used for detection. This ELISA enabled detection of nattokinase at 1 ng/mL. We believe that the novel mAbs developed in this study will be useful in future for elucidating nattokinase function.

Nattokinase prevents β-amyloid peptide (Aβ1-42) induced neuropsychiatric complications, neuroinflammation and BDNF signalling disruption in mice

Alzheimer's disease (AD) is a chronic and progressive neurodegenerative disorder characterized by abnormal accumulation of extracellular β-amyloid (Aβ) plaques and neuronal damage. Although AD is typically considered a cognitive neurodegenerative disorder, almost all people diagnosed with AD develop neuropsychiatric complications at some stage in their life span. The present study investigated the effect of chronic Nattokinase (NK) administration on β-Amyloid peptide (Aβ1-42) induced neuropsychiatric conditions (depression-like behaviour, anxiety, and memory impairment) in mice. Aβ1-42 peptide injected mice demonstrated depression, anxiety, and impairment of cognitive abilities evaluated as increased immobility time in forced swim test (FST), decreased open arm time/entries in elevated plus maze (EPM) and reference and working memory error in radial arm maze (RAM) respectively with elevation in Interleukin-6 (IL-6), Tumour necrosis factor-α (TNF-α), reduction in Interleukin-10 (IL-10) and Brain-derived neurotrophic factor (BDNF) immunocontent within the hippocampus. Chronic administration of NK (50-100 mg/kg, i.p.) from day 8-27, prevented depression-like behaviour, anxiety, and memory impairment and normalized the neurochemical alteration within the hippocampus of mice injected with Aβ1-42 peptide. The effect of NK on psychiatric complications, learning, and memory was comparable to peripheral donepezil treatment. This study suggests that NK improves learning, memory impairment, and neuropsychiatric complications possibly through the downregulation of neuroinflammatory pathways and restoring BDNF signalling in AD.

The Role of Nrf2/sMAF Signalling in Retina Ageing and Retinal Diseases

Age-related diseases, such as Parkinson's disease, Alzheimer's disease, cardiovascular diseases, cancers, and age-related macular disease, have become increasingly prominent as the population ages. Oxygen is essential for living organisms, but it may also cause disease when it is transformed into reactive oxygen species via biological processes in cells. Most of the production of ROS occurs in mitochondrial complexes I and III. The accumulation of ROS in cells causes oxidative stress, which plays a crucial role in human ageing and many diseases. Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a key antioxidant transcription factor that plays a central role in many diseases and ageing in general. It regulates many downstream antioxidative enzymes when cells are exposed to oxidative stress. A basic-region leucine zipper (bZIP) transcription factor, MAF, specifically the small MAF subfamily (sMAFs), forms heterodimers with Nrf2, which bind with Maf-recognition elements (MAREs) in response to oxidative stress. The role of this complex in the human retina remains unclear. This review summarises the current knowledge about Nrf2 and its downstream signalling, especially its cofactor-MAF, in ageing and diseases, with a focus on the retina. Since Nrf2 is the master regulator of redox homeostasis in cells, we hypothesise that targeting Nrf2 is a promising therapeutic approach for many age-related diseases.

Microbial nattokinase: from synthesis to potential application

Nattokinase (NK) is an alkaline serine protease with strong thrombolytic activity produced by Bacillus spp. or Pseudomonas spp. It is a potential therapeutic agent for thrombotic diseases because of its safety, economy, and lack of side effects. Herein, a comprehensive summary and analysis of the reports surrounding NK were presented, and the physical-chemical properties and producers of NK were first described. The process and mechanism of NK synthesis were summarized, but these are vague and not specific enough. Further results may be achieved if detection techniques such as multi-omics are used to explore the process of NK synthesis. The purification of NK has problems such as a complicated operation and low recovery rate, which were found when summarizing the techniques to improve the quality of finished products. If multiple simple and efficient precipitation methods and purification materials are combined to purify NK, it may be possible to solve the current challenges. Additionally, the application potential of NK in biomedicine was reviewed, but functional foods with NK are challenging for acceptance in daily life due to their unpleasant odor. Accordingly, multi-strain combination fermentation or food flavoring agents can improve the odor of fermented foods and increase people's acceptance of them. Finally, the possible future directions focused on NK studies were proposed and provided suggestions for subsequent researchers.

Protective Effect of NO2-OA on Oxidative Stress, Gliosis, and Pro-Angiogenic Response in Müller Glial Cells

Inflammation and oxidative and nitrosative stress are involved in the pathogenesis of proliferative retinopathies (PR). In PR, a loss of balance between pro-angiogenic and anti-angiogenic factors favors the secretion of vascular endothelial growth factor (VEGF). This vascular change results in alterations in the blood-retinal barrier, with extravasation of plasma proteins such as α₂-macroglobulin (α₂M) and gliosis in Müller glial cells (MGCs, such as MIO-M1). It is well known that MGCs play important roles in healthy and sick retinas, including in PR. Nitro-fatty acids are electrophilic lipid mediators with anti-inflammatory and cytoprotective properties. Our aim was to investigate whether nitro-oleic acid (NO₂-OA) is beneficial against oxidative stress, gliosis, and the pro-angiogenic response in MGCs. Pure synthetic NO₂-OA increased HO-1 expression in a time- and concentration-dependent manner, which was abrogated by the Nrf2 inhibitor trigonelline. In response to phorbol 12-myristate 13-acetate (PMA) and lipopolysaccharide (LPS), NO₂-OA prevented the ROS increase and reduced the gliosis induced by α₂M. Finally, when hypoxic MGCs were incubated with NO₂-OA, the increase in VEGF mRNA expression was not affected, but under hypoxia and inflammation (IL-1β), NO₂-OA significantly reduced VEGF mRNA levels. Furthermore, NO₂-OA inhibited endothelial cell (BAEC) tubulogenesis. Our results highlight NO₂-OA's protective effect on oxidative damage, gliosis; and the exacerbated pro-angiogenic response in MGCs.

Production, purification, and functional properties of microbial fibrinolytic enzymes produced by microorganism obtained from soy-based fermented foods: developments and challenges

According to the World Health Organization, cardiovascular disease (CVD) has become a major cause of chronic illness around the globe. It has been reported that soy-based fermented food (SFF) is very effective in preventing thrombus (one of the most important contributing factors to CVD), which are mainly attributed to the bioactive substances, especially the fibrinolytic enzymes (FE) generated by microorganisms during the fermentation process of soybean food. This paper therefore mainly reviewed the microbial fibrinolytic enzymes (MFE) from SFF. We first discuss the use of microbial fermentation to produce FE, with an emphasis on the strains involved. The production, purification, physicochemical properties, structure-functional attributes, functional properties and possible application of MFE from SFF are then discussed. Finally, current limitations and future perspectives for the production, purification, and the practical application of MFE are discussed. MFE from SFF pose multiple health benefits, including thrombolysis, antihypertension, anti-inflammatory, anti-hyperlipidemia, anticancer, neuroprotective, antiviral and other activities. Therefore, they exhibit great potential for functional foods and nutraceutical applications, especially foods with CVDs prevention potential.

Nattokinase attenuates bisphenol A or gamma irradiation-mediated hepatic and neural toxicity by activation of Nrf2 and suppression of inflammatory mediators in rats

Nattokinase (NK), a protease enzyme produced by Bacillus subtilis, has various biological effects such as lipid-lowering activity, antihypertensive, antiplatelet/anticoagulant, and neuroprotective effects. Exposure to environmental toxicants such as bisphenol A (BPA) or γ-radiation (IR) causes multi-organ toxicity through several mechanisms such as impairment of oxidative status, signaling pathways, and hepatic and neuronal functions as well as disruption of the inflammatory responses. Therefore, this study is designed to evaluate the ameliorative effect of NK against BPA- or IR-induced liver and brain damage in rats. Serum ammonia level and liver function tests were measured in addition to brain oxidative stress markers, amyloid-beta, tau protein, and neuroinflammatory mediators. Moreover, relative quantification of brain nuclear factor-erythroid 2-related factor-2 (Nrf2)/heme oxygenase-1 (HO-1) genes, as well as apoptotic markers in brain tissue, was carried out in addition to histopathological examination. The results showed that NK improved liver functions, impaired oxidative status, the cholinergic deficits, and minified the misfolded proteins aggregates. Furthermore, NK alleviated the neuroinflammation via modulating NF-κB/Nrf2/HO-1 pathway and glial cell activation in addition to their antiapoptotic effect. Collectively, the current results revealed the protective effect of NK against hepatic and neurotoxicity derived from BPA or IR.

Reduction of Laser-Induced Choroidal Neovascularization in Mice With Erythropoietin RNA Interference

PURPOSE

The purpose of this study was to evaluate the pathological involvement of erythropoietin (EPO) in experimental choroidal neovascularization (CNV) and its association with neovascular age-related macular degeneration (AMD) and polypoidal choroidal vasculopathy (PCV) in the Chinese population.

METHODS

Treatment effect of recombinant EPO protein were assessed by human umbilical vein endothelial cell (HUVEC) proliferation, migration, and tube formation, and ex vivo choroid-sprouting ability. The effect of intravitreal injection of Epo siRNA against neovascularization was evaluated in the laser-induced CNV mouse model. In addition, the association of EPO variants with neovascular AMD and PCV was determined.

RESULTS

Exogenous supplementation of EPO significantly enhanced the migration and tube formation of HUVECs and promoted ex vivo choroid sprouting in mouse retinal pigment epithelium (RPE)-choroid-sclera complex culture. In the experimental CNV mouse model, Epo expression was found to be significantly upregulated by 3.5-folds in RPE-choroid-sclera complex at day 10 after laser induction as compared to the baseline. Immunofluorescence analysis showed that Epo was mainly expressed around the vascular endothelial cells in the RPE-choroid-sclera complex. Intravitreal injection of siRNA targeting Epo reduced 40% Epo expression and 40% CNV lesion areas as compared to the scramble control. However, EPO variants were not associated with neovascular AMD nor PCV in the Chinese population.

CONCLUSIONS

This study revealed the promotion of human endothelial cell tube formation in vitro and choroid sprouting ex vivo by EPO, and the reduction of laser-induced CNV in vivo by Epo RNA interference.

TRANSLATIONAL RELEVANCE

Targeting EPO could be a potential additional treatment for CNV-related diseases.

Biotechnology, Bioengineering and Applications of Bacillus Nattokinase

Thrombosis has threatened human health in past decades. Bacillus nattokinase is a potential low-cost thrombolytic drug without side-effects and has been introduced into the consumer market as a functional food or dietary supplement. This review firstly summarizes the biodiversity of sources and the fermentation process of nattokinase, and systematically elucidates the structure, catalytic mechanism and enzymatic properties of nattokinase. In view of the problems of low fermentation yield, insufficient activity and stability of nattokinase, this review discusses the heterologous expression of nattokinase in different microbial hosts and summarizes the protein and genetic engineering progress of nattokinase-producing strains. Finally, this review summarizes the clinical applications of nattokinase.

Neurosensory Alterations in Retinopathy of Prematurity: A Window to Neurological Impairments Associated to Preterm Birth

Retinopathy of prematurity (ROP) is one of the main blinding diseases affecting preterm newborns and is classically considered a vascular disorder. The premature exposure to the extrauterine environment, which is hyperoxic in respect to the intrauterine environment, triggers a cascade of events leading to retinal ischemia which, in turn, makes the retina hypoxic thus setting off angiogenic processes. However, many children with a history of ROP show persistent vision impairment, and there is evidence of an association between ROP and neurosensory disabilities. This is not surprising given the strict relationship between neuronal function and an adequate blood supply. In the present work, we revised literature data evidencing to what extent ROP can be considered a neurodegenerative disease, also taking advantage from data obtained in preclinical models of ROP. The involvement of different retinal cell populations in triggering the neuronal damage in ROP was described along with the neurological outcomes associated to ROP. The situation of ROP in Italy was assessed as well.

Recent Advances in Nattokinase-Enriched Fermented Soybean Foods: A Review

With the dramatic increase in mortality of cardiovascular diseases (CVDs) caused by thrombus, this has sparked an interest in seeking more effective thrombolytic drugs or dietary nutriments. The dietary consumption of natto, a traditional Bacillus-fermented food (BFF), can reduce the risk of CVDs. Nattokinase (NK), a natural, safe, efficient and cost-effective thrombolytic enzyme, is the most bioactive ingredient in natto. NK has progressively been considered to have potentially beneficial cardiovascular effects. Microbial synthesis is a cost-effective method of producing NK. Bacillus spp. are the main production strains. While microbial synthesis of NK has been thoroughly explored, NK yield, activity and stability are the critical restrictions. Multiple optimization strategies are an attempt to tackle the current problems to meet commercial demands. We focus on the recent advances in NK, including fermented soybean foods, production strains, optimization strategies, extraction and purification, activity maintenance, biological functions, and safety assessment of NK. In addition, this review systematically discussed the challenges and prospects of NK in actual application. Due to the continuous exploration and rapid progress of NK, NK is expected to be a natural future alternative to CVDs.

Fermented food: Should patients with cardiometabolic diseases go back to an early neolithic diet?

Fermentation has been used since the Early Neolithic period to preserve foods. It has inherent organoleptic and nutritive properties that bestow health benefits, including reducing inflammation and oxidative stress, supporting the growth of salutogenic microbiota, enhancing intestinal mucosal protection and promoting beneficial immunometabolic health effects. The fermentation of food with specific microbiota increases the production salutogenic bioactive compounds that can activate Nrf2 mediated cytoprotective responses and mitigate the effects of the 'diseasome of aging' and its associated inflammageing, which presents as a prominent feature of obesity, type-2 diabetes, cardiovascular and chronic kidney disease. This review discusses the importance of fermented food in improving health span, with special reference to cardiometabolic diseases.