MTOR-independent induction of autophagy in trabecular meshwork cells subjected to biaxial stretch

AbstractThe trabecular meshwork (TM) is part of a complex tissue that controls the exit of aqueous humor from the anterior chamber of the eye, and therefore helps maintaining intraocular pressure (IOP). Because of variations in IOP with changing pressure gradients and fluid movement, the TM and its contained cells undergo morphological deformations, resulting in distention and stretching. It is therefore essential for TM cells to continuously detect and respond to these mechanical forces and adapt their physiology to maintain proper cellular function and protect against mechanical injury. Here we demonstrate the activation of autophagy, a pro-survival pathway responsible for the degradation of long-lived proteins and organelles, in TM cells when subjected to biaxial static stretch (20% elongation), as well as in high-pressure perfused eyes (30mmHg). Morphological and biochemical markers for autophagy found in the stretched cells include elevated LC3-II levels, increased autophagic flux, and the presence of autophagic figures in electron micrographs. Furthermore, our results indicate that the stretch-induced autophagy in TM cells occurs in an MTOR- and BAG3-independent manner. We hypothesize that activation of autophagy is part of the physiological response that allows TM cells to cope and adapt to mechanical forces

Rare eye diseases in India: A concise review of genes and genetics

Rare eye diseases (REDs) are mostly progressive and are the leading cause of irreversible blindness. The disease onset can vary from early childhood to late adulthood. A high rate of consanguinity contributes to India's predisposition to RED. Most gene variations causing REDs are monogenic and, in some cases, digenic. All three types of Mendelian inheritance have been reported in REDs. Some of the REDs are related to systemic illness with variable phenotypes in affected family members. Approximately, 50% of the children affected by REDs show associated phenotypes at the early stages of the disease. A precise clinical diagnosis becomes challenging due to high clinical and genetic heterogeneity. Technological advances, such as next-generation sequencing (NGS), have improved genetic and genomic testing for REDs, thereby aiding in determining the underlying causative gene variants. It is noteworthy that genetic testing together with genetic counseling facilitates a more personalized approach in the accurate diagnosis and management of the disease. In this review, we discuss REDs identified in the Indian population and their underlying genetic etiology

Targeted next generation sequencing identifies novel mutations in Indian patients with retinal dystrophies

Retinal dystrophies (RD) are a group of inherited ocular disorders of the retina causing blindness in more than 2 million people worldwide. RDs are characterized by clinical variability and progressive vision loss. It is associated with high degree of genetic heterogeneity. In order to correlate RDs clinically and genetically and to develop novel therapeutic approaches, genetic testing is of utmost importance. Prior requisite of a genetic test is genetic counselling. The proband and family members underwent genetic counselling including a detailed family history. Pre-test education was vital to help these families understand the importance of genetic test for the proband and validation of the report by testing the parents/siblings blood samples to confirm the genetic mutation. We performed targeted next-generation sequencing (NGS) in clinically confirmed 21 unrelated patients who showed different forms of RD and validated in their family members using panel comprising 184 genes, which covered previously associated genes with retinal disease. The sequencing analysis revealed a total of 21 different mutations in patients with RDs including Leber’s Congenital Amaurosis, Cone-Rod dystrophy, Retinitis Pigmentosa, Achromatopsia and Stargardt disease. Among these, seven mutations were unreported and fourteen variants were reported. We found five novel mutations with existing spectrum of gene mutations identified in Indian patients with the characteristic features of RDs. The knowledge of the pathogenic gene mutation in the affected family member was used to correlate with the proband’s clinical diagnosis, to screen other family members suspected of having similar symptoms and also for carrier testing. In some cases of retinal dystrophy with overlapping clinical symptoms, the genetic report was used to confirm the RD. Post-test genetic counselling was done to discuss the implications of the genetic mutation on the prognosis and management of the RD

Chloroquine Protects Human Corneal Epithelial Cells from Desiccation Stress Induced Inflammation without Altering the Autophagy Flux

Dry eye disease (DED) is a multifactorial ocular surface disorder affecting millions of individuals worldwide. Inflammation has been associated with dry eye and anti-inflammatory drugs are now being targeted as the alternate therapeutic approach for dry eye condition. In this study, we have explored the anti-inflammatory and autophagy modulating effect of chloroquine (CQ) in human corneal epithelial and human corneal fibroblasts cells exposed to desiccation stress, (an in-vitro model for DED). Gene and protein expression profiling of inflammatory and autophagy related molecular factors were analyzed in HCE-T and primary HCF cells exposed to desiccation stress with and without CQ treatment. HCE-T and HCF cells exposed to desiccation stress exhibited increased levels of activated p65, TNF-α, MCP-1, MMP-9, and IL-6. Further, treatment with CQ decreased the levels of active p65, TNF-α, MCP-1, and MMP-9 in cells underdesiccation stress. Increased levels of LC3B and LAMP1 markers in HCE-T cells exposed to desiccation stress suggest activation of autophagy and the addition of CQ did not alter these levels. Changes in the phosphorylation levels of MAPKinase and mTOR pathway proteins were found in HCE-T cells under desiccation stress with or without CQ treatment. Taken together, the data suggests that HCE-T cells under desiccation stress showed NFκB mediated inflammation, which was rescued through the anti-inflammatory effect of CQ without altering the autophagy flux. Therefore, CQ may be used as an alternate therapeutic management for dry eye condition

Modulation of inflammation and autophagy pathways by trehalose containing eye drop formulation in corneal epithelial cells: implications for dry eye disease

Ocular surface inflammation is an immunological perturbation activated in response to various adverse conditions and is a key biomarker to understand the disease pathology and its underlying immunological landscape [1]. The molecular link between Inflammation and autophagy, often implicated in disease conditions, is poorly understood. The aim of this study is to understand the regulation of inflammation signaling pathways by using a well-established modulator of autophagy, trehalose (TRE), on desiccation stress-induced inflammation in SV40 immortalized human corneal epithelial cells. To mimic the dry eye condition, HCE cells were exposed to desiccation stress at 80% confluency in a six well tissue culture plate. The medium was completely aspirated and cells were kept for drying at room temperature for 10 min. Fresh medium with TRE was added and incubated for 6 hrs. The regulation of induced inflammatory and autophagic gene expression and protein activation by TRE formulation (1.2%) was studied. Optimal drug treatment concentrations were determined by dose escalation cytotoxicity studies. Gene expression was evaluated by quantitative PCR, while protein expression and functions were tested by immunoblotting and fluorescence imaging (Cyto-ID, Lysotracker Red). TRE formulation was able to rescue the morphological changes due to desiccation stress. Live to dead cell ratio increased upon TRE treatment. TRE treatment reduced inflammation induced gene expression of IL-6 (2%), MCP-1 (33.31%), IL-8 (9.56%), MMP-9 (18.96%), and TNFα (58.16%) in HCE. Active form of p38, p44/42, and p65 protein levels were altered significantly by TRE treatment. LAMP1 and LC3 autophagy protein markers were also altered with desiccation stress and TRE treatment. The data demonstrate that TRE formulation is effective in reducing desiccation stress induced inflammation in HCE. Further increased phosphorylation of p38, p44/42 and elevated levels of LC3 and LAMP1 suggest that induction of autophagy. This could be a protective mechanism of autophagy in the desiccation stress model. All together our data suggest that TRE may have a novel role on reducing inflammation through autophagy in HCE. Therefore, TRE might be a potential therapeutic for ocular surface treatment

Genetic analysis and clinical phenotype of two Indian families with X-linked choroideremia

Purpose: This study aims to describe the phenotype and genotype of two Indian families affected with X-linked choroideremia (CHM). Materials and Methods: In these two families, the affected individuals and unaffected family members underwent a comprehensive ophthalmic examination including an optical coherence tomography (OCT) and electroretinogram. Blood samples were collected from the families for genetic analysis. Next generation sequencing (NGS) was done using a panel of 184 genes, which covered previously associated genes with retinal dystrophies. Sequencing data were analyzed for the CHM, RPGR, and RP2 genes that have been implicated in CHM and X-linked retinitis pigmentosa (XLRP), respectively. The identified variants were confirmed by Sanger sequencing in available individuals and unrelated controls. Results: In two unrelated male patients, NGS analysis revealed a previously reported 3'-splice site change c.820-1G>C in the CHM gene in the first family and hemizygous mutation c.653G>C (p.Ser218X) in the second family. The asymptomatic family members were carriers for these mutations. Spectral domain-OCT showed loss of outer retina, preservation of the inner retina, and choroidal thinning in the affected males and retinal pigment epithelial changes in the asymptomatic carriers. The identified mutations were not present in 100 controls of Indian origin. There were no potential mutations found in XLRP-associated (RPGR and RP2) genes. Conclusion: This report describes the genotype and phenotype findings in patients with CHM from India. The identified genetic mutation leads to lack of Rab escort protein-1 (REP-1) or affects the production of a REP-1 protein that is likely to cause retinal abnormalities in patients

Genetic and genomic perspective to understand the molecular pathogenesis of keratoconus

Keratoconus (KC; Mendelian Inheritance in Man (OMIM) 14830) is a bilateral, progressive corneal defect affecting all ethnic groups around the world. It is the leading cause of corneal transplantation. The age of onset is at puberty, and the disorder is progressive until the 3 rd -4 th decade of life when it usually arrests. It is one of the major ocular problems with significant social and economic impacts as the disease affects young generation. Although genetic and environmental factors are associated with KC, but the precise etiology is still elusive. Results from complex segregation analysis suggests that genetic abnormalities may play an essential role in the susceptibility to KC. Due to genetic heterogeneity, a recent study revealed 17 different genomic loci identified in KC families by linkage mapping in various populations. The focus of this review is to provide a concise update on the current knowledge of the genetic basis of KC and genomic approaches to understand the disease pathogenesis