Diagnostic efficacy of elevated serum angiotensin-converting enzyme and lymphopenia between presumed sarcoid uveitis and presumed tubercular uveitis.

PURPOSE: To evaluate the diagnostic efficacy of elevated serum angiotensin-converting enzyme (sACE) and lymphopenia in presumed sarcoid and tubercular uveitis. METHODS: A single-centre retrospective study was conducted on a cohort of 755 adult patients with uveitis between January 2019 and June 2020. Demographic, clinical and laboratory data were retrieved from our hospital database. Measurements of serum angiotensin-converting enzyme (sACE) and lymphocyte counts were analysed. RESULTS: The mean age of the patients was 41 ± 13 years. Presumed sarcoid uveitis was diagnosed in 50 (7%) patients, presumed tubercular uveitis in 222 (29.4%) and other uveitic entities noted in 483 (64%). Intermediate and posterior uveitis were the most common anatomical diagnosis in presumed sarcoid uveitis (59% and 20%, respectively) and in presumed tubercular uveitis (46% and 38%, respectively). Elevated sACE was noted in 76% of presumed sarcoid uveitis and 46% in presumed tubercular uveitis. The combination of high serum angiotensin-converting enzyme along with lymphopenia was only in 17% in presumed sarcoid uveitis and 9.7% in presumed tubercular uveitis. sACE was found to be a significant risk factor for presumed sarcoid uveitis with an odds ratio of 3.603 (p < 0.002), and in presumed tubercular uveitis odds ratio was not significant with odds ratio of 1.19. Lymphopenia was not found to be a significant factor in both groups. CONCLUSION: Elevated sACE activity was an independent risk factor for presumed sarcoid uveitis over lymphopenia alone or in combination with lymphopenia.

Exogenous administration of hydrogen sulfide alleviates homocysteine induced inflammation in ARPE-19 cells.

Plasma homocysteine (Hcy) is an independent risk factor for Age related macular degeneration (AMD) and an inducer of inflammation. Homocysteine catabolism releases hydrogen sulfide (H2S). H2S has controversial effects on inflammation. In this study we have analysed the endogenous and exogenous H2S in modulating inflammation using adult retinal pigment epithelial (ARPE-19) cells as an in vitro model for AMD. ARPE-19 cells were treated with various concentrations of Hcy (15, 30 and 50 µM) for 3 h. Expression of Hcy transulfuration genes (CBS, CSE) by qPCR and western blot. H2S levels were measured using Free Radical Analyzer System (WPI, USA). The inflammatory markers (IL-6 and IL-8) were evaluated using real-time PCR and ELISA. Hcy exposure increased CBS protein expression, hydrogen sulfide levels and pro-inflammatory cytokines, modulating CBS by silencing did not alter H2S levels, but inhibition of CSE with PAG inhibited H2S production and decreased cytokine (IL-6 and IL-8) levels. On the contrary exogenous supply of hydrogen sulfide with NaHS and by compound 1c showed anti-inflammatory effects even in the presence of Hcy. This study shows that exogenous delivery of H2S decreases inflammation in retinal pigment epithelial cells on exposure to Hcy in ARPE-19 cells.

Unveiling the therapeutic potential of a mutated paraoxonase 2 in diabetic retinopathy: Defying glycation, mitigating oxidative stress, ER stress and inflammation.

Paraoxonase 2 (PON2) is an intracellular anti-oxidant protein ubiquitously expressed in all cells and reduces reactive oxygen species, endoplasmic reticulum (ER) stress, further improves mitochondrial function and thereby shows anti-apoptotic function. In diabetes and its complications this PON gets glycated and becomes in effective. The PON activity is reported to be reduced in diabetic retinopathy and we have earlier showed Carboxy methyl lysine (AGE) decreased PON2 expression and activity in Human retinal endothelial cells (HREC) . In this study, we have designed and developed a mutated PON2 by in silico and in vitro approach which can resist glycation. Where in glycation-prone residues in PON2 was predicted using in silico analyses and a mutated PON2 was developed using in vitro site directed mutagenesis (SDM) assay mPON2 (mutant PON2-PON2-K70A) and its efficacy was compared with wPON2 (wild type PON2). CML glycated wPON2 and reduced its activity when compared with mPON2 in HREC confirmed by immunoprecipitation and in vitro experiments. Additionally, mPON2 interaction efficiency with its substrates was higher than wPON2 by insilico assay and demonstrated enhanced inhibition against CML-induced oxidative stress, ER stress, pro-inflammation, and mitochondrial fission than wPON2 by invitro assay. Further mPON2 showed increased inhibition of phosphorylation of NFĸB induced by CML. Our investigation establishes that the over expression of mPON2 in HREC can defy glycation and therefore mitigate ER stress and inflammation against CML than endogenous wPON2. These findings imply that mPON2 can be a beneficial therapeutic target against diabetic retinopathy.

Paraoxonase 2 protects against the CML mediated mitochondrial dysfunction through modulating JNK pathway in human retinal cells.

BACKGROUND: Paraoxonase 2 (PON2) a known anti-apoptotic protein, has not been explored against Nε-(carboxymethyl)lysine (CML), induced mitochondrial dysfunction and apoptosis in human retinal cells. Hence this present study aims to investigate the potential role of PON2 in mitigating CML-induced mitochondrial dysfunction in these cells. METHODS: PON2 protein was quantified in HRECs (Human retinal endothelial cells), ARPE-19 (Retinal pigment epithelial cells) cells upon CML treatment and also in cadaveric diabetic retina vs respective controls. ROS production, mitochondrial membrane potential (MMP), mitochondrial permeability transition pore (mPTP) opening, the release of Cyt-c, Bax, Caspase-3, Fis1, Mfn1, Mfn2, mitochondrial morphology, and the signaling pathway was assessed using DCFDA, JC-1, CoCl2, immunofluorescence or western blotting analysis in both loss-of-function or gain-of-function experiments. RESULTS: PON2 protein was downregulated in HREC and ARPE-19 cells upon CML treatment as well as in the diabetic retina (p = 0.035). Decrease in PON2 augments Fis1 expression resulting in fragmentation of mitochondria and enhances the ROS production, decreases MMP, facilitates mPTP opening, and induces the release of Cyt-c, which activates the pro-apoptotic pathway. Whereas PON2 overexpression similar to SP600125 (a specific JNK inhibitor) was able to decrease Fis1 (p = 0.036) and reverse the Bcl-2 and Bax ratio, and inhibit the JNK1/2 signaling pathway. CONCLUSION: Our results confirm that PON2 has an anti-apoptotic role against the CML mediated mitochondrial dysfunction and inhibits apoptosis through the JNK-Fis1 axis. GENERAL SIGNIFICANCE: We hypothesis that enhancing PON2 may provide a better therapeutic potential against diabetic vascular disease.

Effect of advanced glycation end product on paraoxonase 2 expression: Its impact on endoplasmic reticulum stress and inflammation in HUVECs.

BACKGROUND: Paraoxonase (PON), an antioxidant enzyme, comprises of three members (PON1, 2 and 3). Hyperglycemia accelerates formation of AGE in diabetes which mediates endothelial dysfunction. PON1 is studied in diabetes due to its association with HDL, lipid peroxidation and vascular complications but PON2 is not explored much. Recently decreased PON2 activity is reported in monocytes of Type 2 diabetes mellitus (T2DM) patients but its regulation by factors like high glucose and AGE has not been studied. AIM: The aim of the current study is to identify the effect of AGEs on PON2 expression and activity and its implications on endothelial dysfunction in HUVECs. MAIN METHODS: HUVECs were exposed to Glycated albumin (GA)/Carboxymethyl lysine (CML) for 24 h to check for PON2 expression. The ER stress markers GRP78 and IRE1α, pro-inflammatory genes MCP-1, IL-6, IL-8, ICAM1, VCAM1 were assessed by qPCR, western blotting/ELISA. Endothelial-leukocyte adhesion and ROS were assessed using Calcein AM and DCFDA method. One-way ANOVA and student's t-test was done using Graphpad Prism. KEY FINDINGS: AGE exposure significantly decreased PON2 expression and activity with increased oxidative stress, ER stress and inflammation. PON2 overexpression significantly reduced ROS, ER stress and inflammation as well as inhibited NFκB, and ERK1/2, phosphorylation induced by GA/CML treatment. Concomitantly, silencing of PON2 accelerated AGEs induced effects. SIGNIFICANCE: This is the first study to show that both GA and CML down regulates the PON2 expression and activity in HUVECs and over expression of PON2 alleviates AGEs induced endothelial dysfunction.