Reduced Annexin A1 Secretion by ABCA1 Causes Retinal Inflammation and Ganglion Cell Apoptosis in a Murine Glaucoma Model

Physiological activation of liver X receptor provides protection against ocular inflammation in uveitic glaucoma

Virus-induced trabeculitis is considered a significant cause of uveitic glaucoma, being marked by a sudden increase in intraocular pressure and relatively mild inflammation in the anterior chamber of the eye. In previous proteome analyses of aqueous humor (AH) derived from Cytomegalovirus (CMV) uveitic glaucoma patients, we observed the liver X receptor (LXR) pathway to be among the most prominently activated canonical pathways. In the present study, we explored the role of the LXR pathway in the etiology of glaucoma in association with ocular inflammation. LXRα/β and ABCA1, the downstream targets of LXR, were distributed throughout the conventional AH outflow pathway of the human eye, and their increased levels in human trabecular meshwork cells in response to CMV infection and -lipopolysaccharide (LPS) treatment. Treatment with an LXR agonist (T091317) suppressed LPS-induced inflammation and this response was reversed under the deficiency of LXRα/LXRβ. Furthermore, in the rat endotoxin uveitis model, the LXR agonist significantly reduced infiltrating cells and expression of proinflammatory cytokines in the iris and retina. These results reveal upregulation of LXR-ABCA1 under inflammatory insult in the conventional AH outflow pathway, and activation of LXR exhibiting an anti-inflammatory effect, implying its essential physiological protective role in glaucoma associated with ocular inflammation.

Research Progress on the Role of Ubiquitination in Eye Diseases

The occurrence and development of ophthalmic diseases are related to the dysfunction of eye tissues. Ubiquitin is an important form of protein post-translational modification, which plays an essential role in the occurrence and development of diseases through specific modification of target proteins. Ubiquitination governs a variety of intracellular signal transduction processes, including proteasome degradation, DNA damage repair, and cell cycle progression. Studies have found that ubiquitin can play a role in eye diseases such as cataracts, glaucoma, keratopathy, retinopathy, and eye tumors. In this paper, the role of protein ubiquitination in eye diseases was reviewed.

The Sirtuin 5 Inhibitor MC3482 Ameliorates Microglia‑induced Neuroinflammation Following Ischaemic Stroke by Upregulating the Succinylation Level of Annexin-A1

In our previous study, we concluded that sirtuin 5 (SIRT5) was highly expressed in microglia following ischaemic stroke, which induced excessive neuroinflammation and neuronal injury. Therefore, SIRT5-targeting interventions should reduce neuroinflammation and protect against ischaemic brain injury. Here, we showed that treatment with a specific SIRT5 inhibitor, MC3482, alleviated microglia-induced neuroinflammation and improved long-term neurological function in a mouse model of stroke. The mice were administrated with either vehicle or 2 mg/kg MC3482 daily for 7 days via lateral ventricular injection following the onset of middle cerebral artery occlusion. The outcome was assessed by a panel of tests, including a neurological outcome score, declarative memory, sensorimotor tests, anxiety-like behavior and a series of inflammatory factors. We observed a significant reduction of infarct size and inflammatory factors, and the improvement of long-term neurological function in the early stages during ischaemic stroke when the mice were treated with MC3482. Mechanistically, the administration of MC3482 suppressed the desuccinylation of annexin-A1, thereby promoting its membrane recruitment and extracellular secretion, which in turn alleviated neuroinflammation during ischaemic stroke. Based on our findings, MC3482 offers promise as an anti-ischaemic stroke treatment that targets directly the disease's underlying factors.

Annexin A1 in the nervous and ocular systems

The therapeutic potential of Annexin A1, an important member of the Annexin superfamily, has become evident in results of experiments with multiple human systems and animal models. The anti-inflammatory and pro-resolving effects of Annexin A1 are characteristic of pathologies involving the nervous system. In this review, we initially describe the expression sites of Annexin A1, then outline the mechanisms by which Annexin A1 maintains the neurological homeostasis through either formyl peptide receptor 2 or other molecular approaches; and, finally, we discuss the neuroregenerative potential qualities of Annexin A1. The eye and the nervous system are anatomically and functionally connected, but the association between visual system pathogenesis, especially in the retina, and Annexin A1 alterations has not been well summarized. Therefore, we explain the beneficial effects of Annexin A1 for ocular diseases, especially for retinal diseases and glaucoma on the basis of published findings, and we explore present and future delivery strategies for Annexin A1 to the retina.

Glaucoma: from pathogenic mechanisms to retinal glial cell response to damage

Glaucoma is a neurodegenerative disease of the retina characterized by the irreversible loss of retinal ganglion cells (RGCs) leading to visual loss. Degeneration of RGCs and loss of their axons, as well as damage and remodeling of the lamina cribrosa are the main events in the pathogenesis of glaucoma. Different molecular pathways are involved in RGC death, which are triggered and exacerbated as a consequence of a number of risk factors such as elevated intraocular pressure (IOP), age, ocular biomechanics, or low ocular perfusion pressure. Increased IOP is one of the most important risk factors associated with this pathology and the only one for which treatment is currently available, nevertheless, on many cases the progression of the disease continues, despite IOP control. Thus, the IOP elevation is not the only trigger of glaucomatous damage, showing the evidence that other factors can induce RGCs death in this pathology, would be involved in the advance of glaucomatous neurodegeneration. The underlying mechanisms driving the neurodegenerative process in glaucoma include ischemia/hypoxia, mitochondrial dysfunction, oxidative stress and neuroinflammation. In glaucoma, like as other neurodegenerative disorders, the immune system is involved and immunoregulation is conducted mainly by glial cells, microglia, astrocytes, and Müller cells. The increase in IOP produces the activation of glial cells in the retinal tissue. Chronic activation of glial cells in glaucoma may provoke a proinflammatory state at the retinal level inducing blood retinal barrier disruption and RGCs death. The modulation of the immune response in glaucoma as well as the activation of glial cells constitute an interesting new approach in the treatment of glaucoma.

Gene therapies and gene product-based drug candidates for normalizing and preserving tissue functions in animal models of ocular hypertension and glaucoma

More than 76 million people worldwide are afflicted with the neurodegenerative eye diseases described and grouped together as glaucoma. A common feature amongst the many forms of glaucoma is chronically elevated intraocular pressure (IOP) within the anterior chamber of the eye that physically damages the retina, optic nerve and parts of the brain connected with visual perception. The mediators of the contusing raised IOP responsible for such damage and loss of vision include locally released inflammatory agents, tissue remodeling enzymes and infiltrating immune cells which damage the retinal ganglion cell (RGC) axons and eventually kill a significant number of the RGCs. Additional culprits include genetic defects of the patient that involve aberrations in receptors, enzymes and/or endogenous ligands and possible over- or under-production of the latter. Other genetic abnormalities may include issues with signal transduction machinery within key cells of critical tissues in the front (e.g. trabecular meshwork [TM] and Schlemm's canal [SC]) and back of the eye (e.g. retinal ganglion cells and their axons). Genome-wide associated studies (GWAS) coupled with next generation sequencing have provided powerful linkage of certain gene defects and polymorphic variants to the onset and progression of diseases of the tissues involved in fluid dynamics in the TM and SC, and many retinal elements (lamina cribosa, optic nerve head) at the back of the eye which cause ocular hypertension (OHT) and glaucomatous optic neuropathy (GON), respectively. Despite the availability of some drugs, fluid drainage microshunts and full surgical techniques to lower and control intraocular pressure, the major modifiable biomarker of open-angle and other forms of glaucoma, their side-effect profiles, less than optimum effectiveness and short duration of action present opportunities to clinically manage the glaucomas with next generation of treatments with high therapeutic indices, including gene therapies. Thus, identification, characterization and deployment of genetic data coupled with traditional drug discovery and novel gene replacement, gene editing and genetic engineering technologies may provide some solutions to the aforementioned problems. These aspects will be discussed in this article.

A cell-penetrating peptide exerts therapeutic effects against ischemic stroke by mediating the lysosomal degradation of sirtuin 5

Stroke is a major public health concern worldwide. The lack of effective therapies heightens the need for new therapeutic agents. Previous study identified sirtuin 5 (SIRT5) as a positive regulator of microglia-induced excessive neuroinflammation following ischemic stroke. Interventions targeting SIRT5 should therefore alleviate neuroinflammation and protect against ischemic stroke. Here, we synthesized a membrane-permeable peptide specifically bound to SIRT5 through a chaperone-mediated autophagy targeting motif (Tat-SIRT5-CTM) and examined its therapeutic effect in vitro and in vivo. First, in primary microglia, Tat-SIRT5-CTM suppressed the binding of SIRT5 with annexin-A1 (ANXA1), leading to SIRT5 degradation and thus inhibition of SIRT5-mediated desuccinylation of ANXA1, followed by increased membrane accumulation and secretion of ANXA1. These changes, in turn, alleviated microglia-induced neuroinflammation. Moreover, following intravenous injection, Tat-SIRT5-CTM could efficiently pass through the blood‒brain barrier. Importantly, systemic administration of Tat-SIRT5-CTM reduced the brain infarct area and neuronal loss, mitigated neurological deficit scores, and improved long-term neurological functions in a mouse model of ischemic stroke. Furthermore, no toxicity was observed when high doses Tat-SIRT5-CTM were injected into nonischemic mice. Collectively, our study reveals the promising efficacy of the peptide-directed lysosomal degradation of SIRT5 and suggests it as an effective therapeutic approach for the treatment of ischemic stroke.

4-Octyl Itaconate and Dimethyl Fumarate Induce Secretion of the Anti-Inflammatory Protein Annexin A1 via NRF2

Annexin A1 is a key anti-inflammatory effector protein that is involved in the anti-inflammatory effects of glucocorticoids. 4-Octyl itaconate (4-OI), a derivative of the endogenous metabolite itaconate, which is abundantly produced by LPS-activated macrophages, has recently been identified as a potent anti-inflammatory agent. The anti-inflammatory effects of 4-OI share a significant overlap with those of dimethyl fumarate (DMF), a derivate of another Krebs cycle metabolite fumarate, which is already in use clinically for the treatment of inflammatory diseases. In this study we show that both 4-OI and DMF induce secretion of the 33-kDa form of annexin A1 from murine bone marrow-derived macrophages, an effect that is much more pronounced in LPS-stimulated cells. We also show that this 4-OI- and DMF-driven annexin A1 secretion is NRF2-dependent and that other means of activating NRF2 give rise to the same response. Lastly, we demonstrate that the cholesterol transporter ABCA1, which has previously been implicated in annexin A1 secretion, is required for this process in macrophages. Our findings contribute to the growing body of knowledge on the anti-inflammatory effects of the Krebs cycle metabolite derivatives 4-OI and DMF.

Natural products: protective effects against ischemia-induced retinal injury

Ischemic retinal damage, a common condition associated with retinal vascular occlusion, glaucoma, diabetic retinopathy, and other eye diseases, threatens the vision of millions of people worldwide. It triggers excessive inflammation, oxidative stress, apoptosis, and vascular dysfunction, leading to the loss and death of retinal ganglion cells. Unfortunately, minority drugs are available for treating retinal ischemic injury diseases, and their safety are limited. Therefore, there is an urgent need to develop more effective treatments for ischemic retinal damage. Natural compounds have been reported to have antioxidant, anti-inflammatory, and antiapoptotic properties that can be used to treat ischemic retinal damage. In addition, many natural compounds have been shown to exhibit biological functions and pharmacological properties relevant to the treatment of cellular and tissue damage. This article reviews the neuroprotective mechanisms of natural compounds involve treating ischemic retinal injury. These natural compounds may serve as treatments for ischemia-induced retinal diseases.

Posttranslational modifications of proteins in diseased retina

Posttranslational modifications (PTMs) are known to constitute a key step in protein biosynthesis and in the regulation of protein functions. Recent breakthroughs in protein purification strategies and current proteome technologies make it possible to identify the proteomics of healthy and diseased retinas. Despite these advantages, the research field identifying sets of posttranslationally modified proteins (PTMomes) related to diseased retinas is significantly lagging, despite knowledge of the major retina PTMome being critical to drug development. In this review, we highlight current updates regarding the PTMomes in three retinal degenerative diseases-namely, diabetic retinopathy (DR), glaucoma, and retinitis pigmentosa (RP). A literature search reveals the necessity to expedite investigations into essential PTMomes in the diseased retina and validate their physiological roles. This knowledge would accelerate the development of treatments for retinal degenerative disorders and the prevention of blindness in affected populations.

Lack of Association of Polymorphism Located Upstream of ABCA1 (rs2472493), in FNDC3B (rs7636836), and Near ANKRD55–MAP3K1 Genes (rs61275591) in Primary Open-Angle Glaucoma Patients of Saudi Origin

Polymorphisms rs2472493 near ABCA1, rs7636836 in FNDC3B, and rs61275591 near the ANKRD55–MAP3K1 genes were previously reported to exhibit genome-wide significance in primary open-angle glaucoma (POAG). Since these polymorphisms have not been investigated in the Arab population of Saudi Arabia, we examined their association with POAG in a Saudi cohort. Genotyping was performed in 152 POAG cases and 246 controls using Taqman real-time assays and their associations with POAG and clinical markers, such as intraocular pressure, cup/disc ratio, and the number of antiglaucoma medications, were tested by statistical methods. There was no association observed between POAG and the minor allele frequencies of rs2472493[G], rs7636836[T], or rs61275591[A]. None of the genetic models such as co-dominant, dominant, recessive, over-dominant, and log-additive demonstrated any genotype link. The Rs2472493 genotype showed a modest association (p = 0.044) with the number of antiglaucoma medications in the POAG group, but no significant genotype effect on post hoc analysis. In addition, a G-T allelic haplotype of rs2472493 (ABCA1) and rs7636836 (FNDC3B) did show an over two-fold increased risk of POAG (odds ratio = 2.18), albeit non-significantly (p = 0.092). Similarly, no other allelic haplotype of the three variants showed any significant association with POAG. Our study did not replicate the genetic association of rs2472493 (ABCA1), rs763683 (FNDC3B), and rs61275591 (ANKRD55–MAP3K1) in POAG and related clinical phenotypes, suggesting that these polymorphisms are not associated with POAG in a Saudi cohort of Arab ethnicity. However, large population-based multicenter studies are needed to validate these results.

Glaucoma and microglia-induced neuroinflammation

Glaucoma is a multifactorial neurodegenerative disease characterized by a progressive optic neuropathy resulting in visual field defects. Elevated intraocular pressure (IOP) is the greatest risk factor for the development of glaucoma, and IOP reduction therapy is the only treatment currently available. However, there are many cases in which retinal degeneration progresses despite sufficient control of IOP. Therefore, it is important to elucidate the pathophysiology of glaucoma that is resistant to current IOP lowering therapies. Experiments using animal glaucoma models show the relationships between microglial neuroinflammatory responses and damage of retinal ganglion cells (RGCs). Inhibition of neuroinflammatory pathways associated with microglial activation appears to be neuroprotective, indicating that microglia may be an important therapeutic target for RGC protection. In this review, we will focus on microglia-induced neuroinflammation in the pathogenesis of glaucoma to offer new insights into the possibility of developing novel neuroprotective therapies targeting microglia.

SMN Deficiency Destabilizes ABCA1 Expression in Human Fibroblasts: Novel Insights in Pathophysiology of Spinal Muscular Atrophy

The deficiency of survival motor neuron protein (SMN) causes spinal muscular atrophy (SMA), a rare neuromuscular disease that affects different organs. SMN is a key player in RNA metabolism regulation. An intriguing aspect of SMN function is its relationship with plasma membrane-associated proteins. Here, we provide a first demonstration that SMN affects the ATP-binding cassette transporter A1, (ABCA1), a membrane protein critically involved in cholesterol homeostasis. In human fibroblasts, we showed that SMN associates to ABCA1 mRNA, and impacts its subcellular distribution. Consistent with the central role of ABCA1 in the efflux of free cholesterol from cells, we observed a cholesterol accumulation in SMN-depleted human fibroblasts. These results were also confirmed in SMA type I patient-derived fibroblasts. These findings not only validate the intimate connection between SMN and plasma membrane-associated proteins, but also highlight a contribution of dysregulated cholesterol efflux in SMA pathophysiology.

Retinal Proteome Analysis Reveals a Region-Specific Change in the Rabbit Myopia Model

Uncovering region-specific changes in the myopic retina can provide clues to the pathogenesis of myopia progression. After imposing form deprivation myopia in the right eye of 6-week-old rabbits, we investigated the proteome profile of each retinal region (central, mid-periphery, and far-periphery retina), using accurate high-resolution mass spectrometry. Protein expression was analyzed using gene ontology and network analysis compared with that of the control, the left eyes. Among 2065 proteins detected from whole retinal samples, 249 differentially expressed proteins (DEPs) were identified: 164 DEPs in the far-periphery, 39 in the mid-periphery, and 83 in the central retina. In network analysis, the far-periphery retina showed the most significant connectivity between DEPs. The regulation of coagulation was the most significant biological process in upregulated DEPs in the far-periphery retina. Proteasome was the most significant Kyoto Encyclopedia of Genes and Genomes pathway in downregulated DEPs in the central retina. Antithrombin-III, fibrinogen gamma chain, and fibrinogen beta chain were identified as hub proteins for myopia progression, which were upregulated in the far-periphery retina. Proteomic analysis in this study suggested that oxidative stress can be the primary pathogenesis of myopia progression and that the far-periphery retina plays a role as the key responder.

Puerarin: A review of its mechanisms of action and clinical studies in ophthalmology

BACKGROUND

Pueraria is the common name of the dried root of either Pueraria montana var. lobata (Willd.) Maesen & S.M.Almeida ex Sanjappa & Predeep (syn. Pueraria lobata (Willd.) Ohwi) or Pueraria montana var. thomsonii (Benth.) M.R.Almeida (syn. Pueraria thomsonii Benth.). Puerarin is a C-glucoside of the isoflavone daidzein extracted from Pueraria. It has been widely investigated to explore its therapeutic role in eye diseases and the molecular mechanisms.

PURPOSE

To collect the available literature from 2000 to 2022 on puerarin in the treatment of ocular diseases and suggest the future required directions to improve its medicinal value.

METHOD

The content of this review was obtained from databases such as Web of Science, PubMed, Google Scholar, China National Knowledge Infrastructure (CNKI), and the Wanfang Database.

RESULTS

The search yielded 428 articles, of which 159 articles were included after excluding duplicate articles and articles related to puerarin but less relevant to the topic of the review. In eleven articles, the bioavailability of puerarin was discussed. Despite puerarin possesses diverse biological activities, its bioavailability on its own is poor. There are 95 articles in which the therapeutic mechanisms of puerarin in ocular diseases was reported. Of these, 54 articles discussed the various signalling pathways related to occular diseases affected by puerarin. The other 41 articles discussed specific biological activities of puerarin. It plays a therapeutic role in ophthalmopathy via regulating nuclear factor kappa-B (NF-ĸB), mitogen-activated protein kinases (MAPKs), PI3K/AKT, JAK/STAT, protein kinase C (PKC) and other related pathways, affecting the expression of tumour necrosis factor α (TNF-α), interleukin-1β (IL-1β), intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1), superoxide dismutase (SOD), B-cell lymphoma-2 (Bcl-2) and other cytokines resulting in anti-inflammatory, antioxidant and anti-apoptotic effects. The clinical applications of puerarin in ophthalmology were discussed in 25 articles. Eleven articles discussed the toxicity of puerarin. The literature suggests that puerarin has a good curative effect and can be used safely in clinical practice.

CONCLUSION

This review has illustrated the diverse applications of puerarin acting on ocular diseases and suggested that puerarin can be used for treating diabetic retinopathy, retinal vascular occlusion, glaucoma and other ocular diseases in the clinic. Some ocular diseases are the result of the combined action of multiple factors, and the effect of puerarin on different factors needs to be further studied to improve a more complete mechanism of action of puerarin. In addition, it is necessary to increase the number of subjects in clinical trials and conduct clinical trials for other ocular diseases. The information presented here will guide future research studies.

Significant Interrelations among Serum Annexin A1, Soluble Receptor for Advanced Glycation End Products (sRAGE) and rs2070600 in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a major cause of death and morbidity; it may be accompanied by oxidative stress and inflammation with or without underlying genetic etiology. Finding circulating biomarkers for COPD that can help early diagnosis and predict exacerbation and association with respiratory functions has been challenging. There were 40 healthy participants and 60 COPD patients in this research. The rs2070600 gene variant was examined by PCR-RFLP. Circulating sRAGE and annexin A1 levels were determined by ELISA. GSH and MDA were determined by spectrophotometry. In COPD patients, sRAGE serum levels were substantially lower, but conversely, annexin A1 levels were much greater than in controls. The rs2070600 gene polymorphism's strong association with COPD was demonstrated by genotyping and allelic frequency distribution. The GA genotype was most distributed in COPD, and it was strongly linked to lower serum sRAGE levels. The interrelation between annexin A1, sRAGE, and COPD could be explained through effects on inflammatory mediators' pathways. The rs2070600 gene polymorphism was found to significantly enhance the risk of COPD. Serum sRAGE and annexin A1 may be considered potential diagnostic tools for COPD. Through impacts on GSH and MDA levels that alter the release of inflammatory factors and, therefore, lung damage, it is possible to explain the relationship between annexin A1, sRAGE, and COPD.

Annexins as potential targets in ocular diseases

Annexins (AnxAs) are Ca2+/phospholipid-binding proteins extensively studied and generally involved in several diseases. Although evidence exists regarding the distribuition of AnxAs in the visual system, their exact roles and the exact cell types of the eye where these proteins are expressed are not well-understood. AnxAs have pro-resolving roles in infectious, autoimmune, degenerative, fibrotic and angiogenic conditions, making them an important target in ocular tissue homeostasis. This review summarizes the current knowledge on the distribution and function of AnxA1-8 isoforms under normal and pathological conditions in the visual system, as well as perspectives for ophthalmologic treatments, including the potential use of the AnxA1 recombinant and/or its mimetic peptide Ac2-26.

The Association between Serum Lipids and Intraocular Pressure in 2 Large United Kingdom Cohorts

PURPOSE

Serum lipids are modifiable, routinely collected blood test features associated with cardiovascular health. We examined the association of commonly collected serum lipid measures (total cholesterol [TC], high-density lipoprotein cholesterol [HDL-C], low-density lipoprotein cholesterol [LDL-C], and triglycerides) with intraocular pressure (IOP).

DESIGN

Cross-sectional study in the UK Biobank and European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk cohorts.

PARTICIPANTS

We included 94 323 participants from the UK Biobank (mean age, 57 years) and 6230 participants from the EPIC-Norfolk (mean age, 68 years) cohorts with data on TC, HDL-C, LDL-C, and triglycerides collected between 2006 and 2009.

METHODS

Multivariate linear regression adjusting for demographic, lifestyle, anthropometric, medical, and ophthalmic covariables was used to examine the associations of serum lipids with corneal-compensated IOP (IOPcc).

MAIN OUTCOME MEASURES

Corneal-compensated IOP.

RESULTS

Higher levels of TC, HDL-C, and LDL-C were associated independently with higher IOPcc in both cohorts after adjustment for key demographic, medical, and lifestyle factors. For each 1-standard deviation increase in TC, HDL-C, and LDL-C, IOPcc was higher by 0.09 mmHg (95% confidence interval [CI], 0.06-0.11 mmHg; P < 0.001), 0.11 mmHg (95% CI, 0.08-0.13 mmHg; P < 0.001), and 0.07 mmHg (95% CI, 0.05-0.09 mmHg; P < 0.001), respectively, in the UK Biobank cohort. In the EPIC-Norfolk cohort, each 1-standard deviation increase in TC, HDL-C, and LDL-C was associated with a higher IOPcc by 0.19 mmHg (95% CI, 0.07-0.31 mmHg; P = 0.001), 0.14 mmHg (95% CI, 0.03-0.25 mmHg; P = 0.016), and 0.17 mmHg (95% CI, 0.06-0.29 mmHg; P = 0.003). An inverse association between triglyceride levels and IOP in the UK Biobank (-0.05 mmHg; 95% CI, -0.08 to -0.03; P < 0.001) was not replicated in the EPIC-Norfolk cohort (P = 0.30).

CONCLUSIONS

Our findings suggest that serum TC, HDL-C, and LDL-C are associated positively with IOP in 2 United Kingdom cohorts and that triglyceride levels may be associated negatively. Future research is required to assess whether these associations are causal in nature.

Evaluation of ABCA1 and FNDC3B Gene Polymorphisms Associated With Pseudoexfoliation Glaucoma and Primary Angle-Closure Glaucoma in a Saudi Cohort

Objective: It is plausible that common disease mechanisms exist in glaucoma pathophysiology. Accordingly, we investigated the genetic association of two previously reported primary open-angle glaucoma (POAG)-related gene polymorphisms, rs2472493 (A > G) in ABCA1 and rs7636836 (C > T) in FNDC3B, in primary angle-closure glaucoma (PACG) and pseudoexfoliation glaucoma (PXG).

Methods: TaqMan genotyping was performed in a total of 442 subjects consisting of 246 healthy controls, 102 PACG patients, and 94 PXG patients. Statistical evaluations were performed to detect allelic and genotype association of the variants with the disease and clinical variables such as intraocular pressure (IOP) and cup/disc ratio.

Results: Overall, there was no allelic or genotype association of these variants in PACG and PXG. However, rs7636836[T] allele significantly increased the risk of PXG among men (p = 0.029, odds ratio [OR] = 2.69, 95% confidence interval = 1.11–6.51). Similarly, rs2472493 and rs7636836 genotypes also showed significant association with PXG among men in over-dominant model (p = 0.031, OR = 1.98, 95% CI = 1.06–3.71) and co-dominant model (p = 0.029, OR = 2.69, 95% CI = 1.11–6.51), respectively. However, none survived Bonferroni’s correction. Besides, the synergic presence of rs2472493[G] and rs7636836[T] alleles (G-T) was found to significantly increase the risk of PACG (p = 0.026, OR = 2.85, 95% CI = 1.09–7.46). No significant genotype influence was observed on IOP and cup/disc ratio.

Conclusion: Our results suggest that the polymorphisms rs2472493 in ABCA1 and rs7636836 in FNDC3B genes may be associated with PXG among men, and a G-T allelic combination may confer an increased risk of PACG in the middle-eastern Saudi cohort. Further research in a larger population-based sample is needed to validate these findings.

Role of ABCA1 in Cardiovascular Disease

Cholesterol homeostasis plays a significant role in cardiovascular disease. Previous studies have indicated that ATP-binding cassette transporter A1 (ABCA1) is one of the most important proteins that maintains cholesterol homeostasis. ABCA1 mediates nascent high-density lipoprotein biogenesis. Upon binding with apolipoprotein A-I, ABCA1 facilitates the efflux of excess intracellular cholesterol and phospholipids and controls the rate-limiting step of reverse cholesterol transport. In addition, ABCA1 interacts with the apolipoprotein receptor and suppresses inflammation through a series of signaling pathways. Thus, ABCA1 may prevent cardiovascular disease by inhibiting inflammation and maintaining lipid homeostasis. Several studies have indicated that post-transcriptional modifications play a critical role in the regulation of ABCA1 transportation and plasma membrane localization, which affects its biological function. Meanwhile, carriers of the loss-of-function ABCA1 gene are often accompanied by decreased expression of ABCA1 and an increased risk of cardiovascular diseases. We summarized the ABCA1 transcription regulation mechanism, mutations, post-translational modifications, and their roles in the development of dyslipidemia, atherosclerosis, ischemia/reperfusion, myocardial infarction, and coronary heart disease.

Analysis of Glaucoma Associated Genes in Response to Inflammation, an Examination of a Public Data Set Derived from Peripheral Blood from Patients with Hepatitis C

Introduction

Glaucoma is the second leading cause of blindness worldwide and despite its prevalence, there are still many unanswered questions related to its pathogenesis. There is evidence that oxidative stress and inflammation play a major role in disease progression. Glaucoma patients from several studies showed altered gene expression in leukocytes, revealing the possibility of using peripheral biomarkers to diagnose or stage glaucoma. The fact that glaucoma is associated with gene expression changes in tissues distant from the retina underscores the possible involvement of systemic oxidative stress and inflammation as potential contributing or compounding factors in glaucoma.

Methods

We assembled a list of oxidative stress and inflammatory markers related to glaucoma based on a review of the literature. In addition, we utilized publicly available data sets of gene expression values collected from peripheral blood mononuclear cells and macrophages from two patient groups: those chronically infected by the hepatitis C virus and those who have cleared it. Activation of the innate immune response can render cells or tissues more responsive to a second delayed proinflammatory stimulus. Additional gene expression data from these cells after subsequent polyinosinic:polycytidylic acid treatment, used to elicit an acute inflammatory response, allowed for the investigation of the acute inflammatory response in these groups. We used fold-change comparison values between the two patient groups to identify genes of interest.

Results

A comparison analysis identified 17 glaucoma biomarkers that were differentially expressed in response to HCV-mediated inflammation. Of these 17, six had significant p-values in the baseline vs treated values. Expression data of these genes were compared between patients who had cleared the Hepatitis C virus versus those who had not and identified three genes of interest for further study.

Discussion

These results support our hypothesis that inflammation secondary to Hepatitis C virus infection affects the expression of glaucoma biomarker genes related to the antioxidant response and inflammation. In addition, they provide several potential targets for further research into understanding the relationship between innate responses to viral infection and inflammatory aspects of glaucoma and for potential use as a predictive biomarker or pharmacological intervention in glaucoma.

Molecular mechanisms for ABCA1-mediated cholesterol efflux

The maintenance of cellular cholesterol homeostasis is essential for normal cell function and viability. Excessive cholesterol accumulation is detrimental to cells and serves as the molecular basis of many diseases, such as atherosclerosis, Alzheimer's disease, and diabetes mellitus. The peripheral cells do not have the ability to degrade cholesterol. Cholesterol efflux is therefore the only pathway to eliminate excessive cholesterol from these cells. This process is predominantly mediated by ATP-binding cassette transporter A1 (ABCA1), an integral membrane protein. ABCA1 is known to transfer intracellular free cholesterol and phospholipids to apolipoprotein A-I (apoA-I) for generating nascent high-density lipoprotein (nHDL) particles. nHDL can accept more free cholesterol from peripheral cells. Free cholesterol is then converted to cholesteryl ester by lecithin:cholesterol acyltransferase to form mature HDL. HDL-bound cholesterol enters the liver for biliary secretion and fecal excretion. Although how cholesterol is transported by ABCA1 to apoA-I remains incompletely understood, nine models have been proposed to explain this effect. In this review, we focus on the current view of the mechanisms underlying ABCA1-mediated cholesterol efflux to provide an important framework for future investigation and lipid-lowering therapy.

ABCA1, ABCG1, and Cholesterol Homeostasis

Cholesterol is a major component of mammalian cell membranes and plays important structural and functional roles. However, excessive cholesterol accumulation is toxic to cells and constitutes the molecular basis for many diseases, especially atherosclerotic cardiovascular disease. Thus, cellular cholesterol is tightly regulated to maintain a homeostasis. Reverse cholesterol transport (RCT) is thought to be one primary pathway to eliminate excessive cholesterol from the body. The first and rate-limiting step of RCT is ATP-binding cassette (ABC) transports A1 (ABCA1)- and ABCG1-dependent cholesterol efflux. In the process, ABCA1 mediates initial transport of cellular cholesterol to apolipoprotein A-I (apoA-I) for forming nascent high-density lipoprotein (HDL) particles, and ABCG1 facilitates subsequent continued cholesterol efflux to HDL for further maturation. In this chapter, we summarize the roles of ABCA1 and ABCG1 in maintaining cellular cholesterol homoeostasis and discuss the underlying mechanisms by which they mediate cholesterol export.

Annexin A Protein Family in Atherosclerosis

Atherosclerosis, a silent chronic vascular pathology, is the cause of the majority of cardiovascular ischaemic events. Atherosclerosis is characterized by a series of deleterious changes in cellularity, including endothelial dysfunction, transmigration of circulating inflammatory cells into the arterial wall, pro-inflammatory cytokines production, lipid accumulation in the intima, vascular local inflammatory response, atherosclerosis-related cells apoptosis and autophagy. Proteins of Annexin A (AnxA) family, the well-known Ca²⁺ phospholipid-binding protein, have many functions in regulating inflammation-related enzymes and cell signaling transduction, thus influencing cell adhesion, migration, differentiation, proliferation and apoptosis. There is now accumulating evidence that some members of the AnxA family, such as AnxA1, AnxA2, AnxA5 and AnxA7, play major roles in the development of atherosclerosis. This article discusses the major roles of AnxA1, AnxA2, AnxA5 and AnxA7, and the multifaceted mechanisms of the main biological process in which they are involved in atherosclerosis. Considering these evidences, it has been proposed that AnxA are drivers- and not merely participator- on the road to atherosclerosis, thus the progression of atherosclerosis may be prevented by targeting the expression or function of the AnxA family proteins.

Contribution of Interleukin-17A to Retinal Degenerative Diseases

Retinal degenerative diseases are a leading cause of vision loss and blindness throughout the world, characterized by chronic and progressive loss of neurons and/or myelin. One of the common features of retinal degenerative diseases and central neurodegenerative diseases is chronic neuroinflammation. Interleukin-17A (IL-17A) is the cytokine most closely related to disease in its family. Accumulating evidence suggests that IL-17A plays a key role in human retinal degenerative diseases, including age-related macular degeneration, diabetic retinopathy and glaucoma. This review aims to provide an overview of the role of IL-17A participating in the pathogenesis of retinal degenerative diseases, which may open new avenues for potential therapeutic interventions.

Association of ABCA1 (rs2472493) and GAS7 (rs9913911) gene variants with primary open-angle glaucoma in a Brazilian population

Purpose

Glaucoma is the world's leading cause of irreversible blindness, with primary open-angle glaucoma (POAG) being the most prevalent subtype. In recent years, there have been advances in knowledge about the genetics involved in POAG, but genetic studies in admixed populations, such as Brazilians, are still rare. This study aimed to evaluate the association of single nucleotide variants (SNV) of the ABCA1 (rs2472493) and GAS7 (rs9913911) genes with POAG in a sample of the Brazilian population. Furthermore, the study aimed to evaluate the relationship between these SNVs and the need for surgical intervention in glaucoma control.

Methods

A cross-sectional association study with 1,009 subjects (505 patients with POAG and 504 controls) was performed. Participants underwent a comprehensive ocular examination, including the need for surgical procedures for intraocular pressure control. Genotyping of SNVs was performed using the TaqMan genotyping assay.

Results

SNV rs9913911 of GAS7 was found to be associated with POAG in the presence of the risk allele A (p = 0.0004) and the AA genotype (p = 0.002). There was no association between SNV rs2472493 of ABCA1 for either the allele risk or genotypes. However, the combination of these variants showed an additive effect on the risk for POAG: ABCA1(GG) + GAS7(AA; p = 0.02), ABCA1(GG) + GAS7(AG; p = 0.003), and ABCA1(AG) + GAS7(AG; p = 0.004). Also, POAG patients carrying the AA genotype of the GAS7 gene required antiglaucomatous surgery more frequently than those without the AA genotype (p = 0.01).

Conclusions

In a Brazilian population sample, there was an association identified between SNV rs9913911 (GAS7) and the risk of POAG, and an additive effect was found when GAS7 was combined with SNV rs2472493 (ABCA1). There was an association between SNV rs9913911 (GAS7) and the risk for antiglaucomatous surgery.

Neutrophils and neutrophil extracellular trap components: Emerging biomarkers and therapeutic targets for age-related eye diseases

Age-related eye diseases, including dry eye, glaucoma, age-related macular degeneration, and diabetic retinopathy, represent a major global health issue based on their increasing prevalence and disabling action. Unraveling the molecular mechanisms underlying these diseases will provide novel opportunities to reduce the burden of age-related eye diseases and improve eye health, contributing to sustainable development goals achievement. The impairment of neutrophil extracellular traps formation/degradation processes seems to be one of these mechanisms. These traps formed by a meshwork of DNA and neutrophil cytosolic granule proteins may exacerbate the inflammatory response promoting chronic inflammation, a pivotal cause of age-related diseases. In this review, we describe current findings that suggest the role of neutrophils and their traps in the pathogenesis of the above-mentioned age-related eye diseases. Furthermore, we discuss why these cells and their constituents could be biomarkers and therapeutic targets for dry eye, glaucoma, age-related macular degeneration, and diabetic retinopathy. We also examine the therapeutic potential of some neutrophil function modulators and provide several recommendations for future research in age-related eye diseases.

Nuclear receptors of NR1 and NR4 subfamilies in the regulation of microglial functions and pathology

This review provides an overview of researches on the NR1 and NR4 nuclear receptors involved in the regulation of microglial functions. Nuclear receptors are attractive candidates for drug targets in the therapies of the central nervous system disorders, because the activation of these receptors is expected to regulate the functions and the phenotypes of microglia, by controlling the expression of specific gene subsets and also by regulating the cellular signaling mechanisms in a nongenomic manner. Several members of NR1 nuclear receptor subfamily have been examined for their ability to regulate microglial functions. For example, stimulation of vitamin D receptor inhibits the production of pro-inflammatory factors and increases the production of anti-inflammatory cytokines. Similar regulatory actions of nuclear receptor ligands on inflammation-related genes have also been reported for other NR1 members such as retinoic acid receptors, peroxisome proliferator-activated receptors (PPARs), and liver X receptors (LXRs). In addition, stimulation of PPARγ and LXRs may also result in increased phagocytic activities of microglia. Consistent with these actions, the agonists at nuclear receptors of NR1 subfamily are shown to produce therapeutic effects on animal models of various neurological disorders such as experimental allergic encephalomyelitis, Alzheimer's disease, Parkinson's disease, and ischemic/hemorrhagic stroke. On the other hand, increasing lines of evidence suggest that the stimulation of NR4 subfamily members of nuclear receptors such as Nur77 and Nurr1 also regulates microglial functions and alleviates neuropathological events in several disease models. Further advancement of these research fields may prove novel therapeutic opportunities.

Glaucoma Heritability: Molecular Mechanisms of Disease

Glaucoma is one of the world’s leading causes of irreversible blindness. A complex, multifactorial disease, the underlying pathogenesis and reasons for disease progression are not fully understood. The most common form of glaucoma, primary open-angle glaucoma (POAG), was traditionally understood to be the result of elevated intraocular pressure (IOP), leading to optic nerve damage and functional vision loss. Recently, researchers have suggested that POAG may have an underlying genetic component. In fact, studies of genetic association and heritability have yielded encouraging results showing that glaucoma may be influenced by genetic factors, and estimates for the heritability of POAG and disease-related endophenotypes show encouraging results. However, the vast majority of the underlying genetic variants and their molecular mechanisms have not been elucidated. Several genes have been suggested to have molecular mechanisms contributing to alterations in key endophenotypes such as IOP (LMX1B, MADD, NR1H3, and SEPT9), and VCDR (ABCA1, ELN, ASAP1, and ATOH7). Still, genetic studies about glaucoma and its molecular mechanisms are limited by the multifactorial nature of the disease and the large number of genes that have been identified to have an association with glaucoma. Therefore, further study into the molecular mechanisms of the disease itself are required for the future development of therapies targeted at genes leading to POAG endophenotypes and, therefore, increased risk of disease.

ANXA1-GSK3β interaction and its involvement in NSCLC metastasis

Although initially discovered and extensively studied for its role in inflammation, Annexin A1 (ANXA1) has been reported to be closely related to cancer in recent years, and its role in cancer is specific to tumor types and tissues. In the present study, we identified ANXA1 as an interaction partner of glycogen synthase kinase 3 beta (GSK3β), a multi-functional serine/threonine kinase tightly associated with cell fate determination and cancer, and assessed the functional significance of GSK3β-ANXA1 interaction in the metastasis of non-small cell lung cancer (NSCLC). We confirmed the interaction between GSK3β and ANXA1 in vitro and in H1299 and A549 cells by Glutathione-S-transferase (GST) pull-down assay and co-immunoprecipitation. We found that ANXA1 negatively regulated the phosphorylation of GSK3β and inhibited the epithelial-mesenchymal transformation (EMT) process and migration and invasion of NSCLC cells. By functional rescue assay, we confirmed that ANXA1 inhibited EMT through the regulation of GSK3β activity and thereby inhibited the migration and invasion of NSCLC cells. Our study sheds light on the function of ANXA1 and GSK3β and provides new elements for the understanding of NSCLC pathogenesis.

Protective role of ABCA1 in ischemic preconditioning is mediated by downregulation of miR-33-5p and miR-135-5p

Ischemic preconditioning (IPC) significantly reduces ischemia–reperfusion injury in the brain by inducing ischemic tolerance. Although emerging evidence suggests that microRNAs (miRNAs) contribute to the pathogenesis of brain ischemia and IPC-induced neuroprotection, the role of miRNAs and their underlying mechanisms are still unclear. IPC was induced in male C57BL/6 mice by brief bilateral common carotid artery occlusion. After 24 h, mice underwent transient middle cerebral artery occlusion followed by 3 h of reperfusion. Expression levels of messenger RNAs (mRNAs) and proteins were examined in the ipsilateral cortex, and mimics and inhibitors of selective miRNAs were transfected into Neuro-2a cells before oxygen–glucose deprivation (OGD). Post-IPC miRNA expression profiling identified neuroprotection-associated changes in miRNA expression in the ipsilateral cortex after ischemic stroke. Among them, miR-33-5p and miR-135b-5p were significantly downregulated by IPC. Inhibition of miR-33-5p and miR-135b-5p expression protected Neuro-2a cells from OGD-induced apoptosis. Inhibition of these two miRNAs significantly increased mRNA and protein levels of ATP-binding cassette subfamily A member 1 (ABCA1), and a binding assay showed that these two miRNAs showed specificity for Abca1 mRNA. Overexpression of ABCA1 decreased the Bax/Bcl2 mRNA ratio and activation of caspase-9 and caspase-3, whereas knockdown of ABCA1 expression increased the Bax/Bcl2 mRNA ratio and the percentage of Neuro-2a cells with a loss of mitochondrial membrane potential after OGD-treatment. In conclusion, ABCA1 expression is regulated by miR-33-5p and miR-135b-5p. Increased ABCA1 expression following IPC exerts a protective influence against cerebral ischemia via suppression of a mitochondria-dependent apoptosis pathway.

Ad- and AAV8-mediated ABCA1 gene therapy in a murine model with retinal ischemia/reperfusion injuries

The anti-inflammatory molecule annexin A1 (ANXA1) determines the ultimate fate of retinal ganglion cell (RGC) in glaucoma. Cytoplasmic and extracellular ANXA1 facilitate resolution of inflammation. However, the nuclear translocation of ANXA1 induces RGC apoptosis in a murine glaucoma model, and the maintenance of ANXA1 secreted in the extracellular environments remains unclear. In this study, we found that intravitreal injection of the recombinant adenovirus vector (Ad)-ATP-binding cassette transporter A1 (ABCA1; carrying full-length ABCA1) improved RGC survival in the ischemia reperfusion (IR) mice model. Upregulation of ABCA1 maintained ANXA1 cytoplasmic location and reduced ANXA1 nuclear translocation, which is due to the decreased binding of ANXA1 with importin β. Moreover, we found that amino acids 903 to 1,344 of ABCA1 interacted with ANXA1 and decreased its nuclear localization. Importantly, intravitreal injection of adenovirus-associated viral (AAV) vector AAV8-ABCA1 (carrying 903 to 1,344 fragments of ABCA1) maintained ANXA1 cytoplasmic location and improved RGC survival in the IR mice model. Thus, overexpression of ABCA1 protects against RGC apoptosis by partially blocking ANXA1 nuclear translocation. This study puts forth a potential gene treatment strategy to prevent RGC apoptosis in glaucoma.

Houttuynia cordata Thunb rescues retinal ganglion cells through inhibiting microglia activation in a rat model of retinal ischemia-reperfusion

AIM

To determine whether Houttuynia cordata Thunb (HCT) can increase the survival of the retinal ganglion cells (RGCs) and inhibit microglia activation following retinal ischemia-reperfusion (RIR) injury.

METHODS

Rat model of RIR was induced by transient elevation of the intraocular pressure (IOP). HCT was orally administered for 2d before the performance of retinal RIR model and once a day for the next 14d. After 14d of RIR injury, the rats were sacrificed for further analysis. Survival RGCs were stained with haematoxylin and eosin (H&E). Apoptosis of RGCs was detected by TUNEL staining. Retinal function was examined by flash-electroretinography (F-ERG). Retinal microglia were labeled using Iba-1, one specific marker for microglia. The mRNA expression levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor alpha (TNF-α), and interleukin 1 beta (IL-1β) were assessed by quantitative real time reverse transcription polymerase chain reaction (qRT-PCR).

RESULTS

Systemic HCT treatment significantly reduced RGCs death by H&E staining and exhibited an anti-apoptotic effect as assessed by TUNEL staining at day 14 after RIR injury. HCT greatly improved the retinal function as examined by F-ERG. The number of activated microglia significantly increased after RIR injury, which was significantly attenuated by HCT treatment. Besides, RIR injury induced a strong upregulation of pro-inflammatory genes TNF-α, iNOS and IL-1β mRNAs at day 14 post injury, which was suppressed by HCT.

CONCLUSION

Neuroprotective effects of HCT encourage the survival of RGCs through inhibiting microglia activation due to RIR injury. Together these results support the use of HCT as promising therapy for the ischemic events of the retina diseases.

Neuronal Epac1 mediates retinal neurodegeneration in mouse models of ocular hypertension

Progressive loss of retinal ganglion cells (RGCs) leads to irreversible visual deficits in glaucoma. Here, we found that the level of cyclic AMP and the activity and expression of its mediator Epac1 were increased in retinas of two mouse models of ocular hypertension. Genetic depletion of Epac1 significantly attenuated ocular hypertension–induced detrimental effects in the retina, including vascular inflammation, neuronal apoptosis and necroptosis, thinning of ganglion cell complex layer, RGC loss, and retinal neuronal dysfunction. With bone marrow transplantation and various Epac1 conditional knockout mice, we further demonstrated that Epac1 in retinal neuronal cells (especially RGCs) was responsible for their death. Consistently, pharmacologic inhibition of Epac activity prevented RGC loss. Moreover, in vitro study on primary RGCs showed that Epac1 activation was sufficient to induce RGC death, which was mechanistically mediated by CaMKII activation. Taken together, these findings indicate that neuronal Epac1 plays a critical role in retinal neurodegeneration and suggest that Epac1 could be considered a target for neuroprotection in glaucoma.

Interleukin-17A: The Key Cytokine in Neurodegenerative Diseases

Neurodegenerative diseases are characterized by the loss of neurons and/or myelin sheath, which deteriorate over time and cause dysfunction. Interleukin 17A is the signature cytokine of a subset of CD4⁺ helper T cells known as Th17 cells, and the IL-17 cytokine family contains six cytokines and five receptors. Recently, several studies have suggested a pivotal role for the interleukin-17A (IL-17A) cytokine family in human inflammatory or autoimmune diseases and neurodegenerative diseases, including psoriasis, rheumatoid arthritis (RA), Alzheimer’s disease (AD), Parkinson’s disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), and glaucoma. Studies in recent years have shown that the mechanism of action of IL-17A is more subtle than simply causing inflammation. Although the specific mechanism of IL-17A in neurodegenerative diseases is still controversial, it is generally accepted now that IL-17A causes diseases by activating glial cells. In this review article, we will focus on the function of IL-17A, in particular the proposed roles of IL-17A, in the pathogenesis of neurodegenerative diseases.

ABCA1 Regulates IOP by Modulating Cav1/eNOS/NO Signaling Pathway

Purpose

This study aimed to investigate the role and pathophysiological mechanism of ATP binding cassette transporter A1 (ABCA1) in regulating the IOP and aqueous humor outflow.

Methods

ABCA1 expression was measured in trabecular meshwork samples obtained from patients with POAG and human donor eyes by Western blot. To further evaluate the functional significance of ABCA1, porcine angular aqueous plexus (AAP) cells, which are equivalent to human Schlemm's canal endothelial cells, were either treated with ABCA1 agonist GW3965 or transduced with lentivirus expressing ABCA1-shRNA. Transendothelial electrical resistance, protein expression, and nitric oxide (NO) concentration were measured. GW3965 was administered by intracameral injection. IOP and aqueous humor outflow facility were also measured.

Results

ABCA1 expression was significantly higher in the trabecular meshwork tissue of patients with POAG compared with controls. ABCA1 upregulation in angular aqueous plexus cells decreased the transendothelial electrical resistance in the angular aqueous plexus monolayers accompanied by a 0.56-fold decrease in caveolin-1 expression and a 2.85-fold and 1.17-fold increase in endothelial NO synthase expression and NO concentration, respectively (n = 3, P < 0.05). Conversely, ABCA1 downregulation increased transendothelial electrical resistance and caveolin-1 expression and decreased endothelial NO synthase expression and NO production (n = 3, P < 0.05). GW3965 decreased IOP and significantly increased conventional outflow facility (P < 0.05).

Conclusions

Regulation of aqueous humor outflow via the caveolin-1/endothelial NO synthase/NO pathway is a newly defined function of ABCA1 that is different from its traditional role in mediating cholesterol efflux. ABCA1 is a compelling, novel therapeutic candidate for the treatment of glaucoma and ocular hypertension.

The crosstalk of ABCA1 and ANXA1: a potential mechanism for protection against atherosclerosis

Atherosclerosis, characterized by the formation of fat-laden plaques, is a chronic inflammatory disease. ABCA1 promotes cholesterol efflux, reduces cellular cholesterol accumulation, and regulates anti-inflammatory activities in an apoA-I- or ANXA1-dependent manner. The latter activity occurs by mediating the efflux of ANXA1, which plays a critical role in anti-inflammatory effects, cholesterol transport, exosome and microparticle secretion, and apoptotic cell clearance. ApoA-I increases ANXA1 expression via the ERK, p38MAPK, AKT, and PKC pathways. ApoA-I regulates the signaling pathways by binding to ABCA1, suggesting that apoA-I increases ANXA1 expression by binding to ABCA1. Furthermore, ANXA1 may increase ABCA1 expression. ANXA1 increases PPARγ expression by modulating STAT6 phosphorylation. PPARγ also increases ANXA1 expression by binding to the promoter of ANXA1. Therefore, ABCA1, PPARγ, and ANXA1 may form a feedback loop and regulate each other. Interestingly, the ANXA1 needs to be externalized to the cell membrane or secreted into the extracellular fluids to exert its anti-inflammatory properties. ABCA1 transports ANXA1 from the cytoplasm to the cell membrane by regulating lipidization and serine phosphorylation, thereby mediating ANXA1 efflux, likely by promoting microparticle and exosome release. The direct role of ABCA1 expression and ANXA1 release in atherosclerosis has been unclear. In this review, we focus on the role of ANXA1 in atheroprogression and its novel interaction with ABCA1, which may be useful for providing basic knowledge for the development of novel therapeutic targets for atherosclerosis and cardiovascular disease.

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.

Puerarin ameliorates retinal ganglion cell damage induced by retinal ischemia/reperfusion through inhibiting the activation of TLR4/NLRP3 inflammasome

AIMS

Retinal ischemia/reperfusion (I/R) injury is common in the development of ophthalmic diseases and potentially causes blindness. In present study, the aim is to investigate the possible protective effects of puerarin on retinal I/R.

MAIN METHODS

Retinal I/R injury was conducted on the left eyes of male Sprague Dawley rats, which were subsequently received treatment with puerarin. After administration, retinal I/R-induced apoptosis, oxidative stress and inflammatory responses were detected. Meanwhile, we purified retinal ganglion cells (RGCs) from 7-day-old rats. After subjected RGCs to oxygen and glucose deprivation/reoxygenation (OGD/R), apoptosis and TLR4/NLRP3 inflammasome activation in RGCs were detected.

KEY FINDINGS

Puerarin prominently suppressed apoptosis, alleviated oxidative stress and suppressed TLR4/NLRP3 inflammasome activation in rats with retinal I/R injury. Consistent with our in vivo study, we found puerarin ameliorated retinal I/R injury through suppressing apoptosis and TLR4/NLRP3 inflammasome activation in RGCs.

SIGNIFICANCE

Our findings reveal that puerarin plays a protective role against retinal I/R injury by alleviating RGC damage, and is beneficial for the treatment of I/R injury-caused ophthalmic diseases.

Butyrate-producing bacteria and the gut-heart axis in atherosclerosis

The gut microbiota plays an important role in controlling atherosclerosis progression to support the link between the gut and coronary heart disease. Recent studies have shown that an imbalance in the gut-heart axis due to the gut microbiota plays an important role in atherosclerosis progression. The gut microbiota promotes the development of atherosclerosis by producing intermediate metabolites, including TMAO, LPS, PAGln and reducing butyrate. TMAO and PAGln might be potential biomarkers of coronary heart disease. Many studies have shown that butyrate-producing bacteria prevent atherosclerosis progression by producing butyrate and maintaining the bacterial balance, the intestinal barrier function and the expression of various genes, including those encoding lipids and those related to immunity, inflammation, differentiation, apoptosis, phagocytosis and efferocytosis. This review focuses on recent advances in our understanding of the interplay between butyrate-producing bacteria and the gut-heart axis in atherosclerosis.

Association of the CAV1-CAV2 locus with normal-tension glaucoma in Chinese and Japanese

BACKGROUND

The CAV1-CAV2 locus has been associated with primary open-angle glaucoma (POAG) and intraocular pressure. However, its association with normal-tension glaucoma (NTG) was inconclusive. Therefore, we evaluated this association in Chinese and Japanese.

METHODS

Two single-nucleotide polymorphisms (SNPs, rs4236601 and rs1052990) from previous genome-wide association studies of POAG were genotyped in a total of 2220 study subjects: a Hong Kong Chinese cohort of 537 NTG patients and 490 controls, a Shantou Chinese cohort of 102 NTG and 731 controls and an Osaka Japanese cohort of 153 NTG and 207 controls. Subgroup analysis by gender was conducted. Outcomes from different cohorts were combined using meta-analysis.

RESULTS

SNP rs4236601 was significantly associated with NTG in the two Chinese cohorts (P_meta = .0019, OR = 4.55, I² = 0). In contrast, rs4236601 was monomorphic in the Osaka cohort. The association of rs1052990 was insignificant in a meta-analysis combining Chinese and Japanese cohorts (P_meta = .81, OR = 1.05; I² = 64%), and the OR tended towards opposite directions between Chinese (OR = 1.26) and Japanese (OR = 0.69). Gender-specific effects of the SNPs were not statistically significant in the logistic regression or Breslow-day tests of ORs (P > .05), although rs4236601 was significant in males (P = .0068; OR = 10.30) but not in females (P = .14; OR = 2.65) in the meta-analysis of Chinese subjects.

CONCLUSIONS

In this study, we confirmed the association of rs4236601 at the CAV1-CAV2 locus with NTG in Chinese. SNP rs4236601 is monomorphic, and rs1052990 tends towards a different direction in the Japanese cohort. Further studies are warranted to verify the ethnic difference and gender-specific effects of this locus.

Reduced expression of annexin A1 promotes gemcitabine and 5-fluorouracil drug resistance of human pancreatic cancer

Intrinsic chemoresistance is the main reason for the failure of human pancreatic ductal adenocarcinoma (PDAC) therapy. To identify the candidate protein, we compared the protein expression profiling of PDAC cells and its distinct surviving cells following primary treatment with gemcitabine (GEM) and 5-fluorouracil (5-FU) by two-dimensional electrophoresis combined with liquid chromatography-mass spectrometry or mass spectrometry. A total of 20 differentially expressed proteins were identified, and annexin A1 (ANXA1) was analyzed for further validation. The functional validation showed that the downregulation of ANXA1 contributes to GEM and 5-FU resistance in PDAC cells through protein kinase C/c-Jun N-terminal kinase/P-glycoprotein signaling pathway. Our findings provide a platform for the further elucidation of the underlying mechanisms of PDAC intrinsic chemoresistance and demonstrated that ANXA1 may be a valid marker for anticancer drug development.