Ischaemia-induced retinal neovascularisation and diabetic retinopathy in mice with conditional knockout of hypoxia-inducible factor-1 in retinal Müller cells

AIMS/HYPOTHESIS

Retinal Müller cells are known to produce inflammatory and angiogenic cytokines, which play important roles in diabetic retinopathy. Hypoxia-inducible factor (HIF)-1 has been shown to play a crucial role in retinal inflammation and neovascularisation. We sought to determine the role of Müller cell-derived HIF-1 in oxygen-induced retinopathy (OIR) and diabetic retinopathy using conditional Hif-1α (also known as Hif1a) knockout (KO) mice.

METHODS

Conditional Hif-1α KO mice were generated by crossing mice expressing cyclisation recombinase (cre, also known as P1_gp003) in Müller cells with floxed Hif-1α mice and used for OIR and streptozotocin-induced diabetes to induce retinal neovascularisation and inflammation, respectively. Abundance of HIF-1α and pro-angiogenic and pro-inflammatory factors was measured by immunoblotting and immunohistochemistry. Retinal neovascularisation was visualised by angiography and quantified by counting pre-retinal nuclei. Retinal inflammation was evaluated by leucostasis and vascular leakage.

RESULTS

While the Hif-1α KO mice showed significantly decreased HIF-1α levels in the retina, they exhibited no apparent histological or visual functional abnormalities under normal conditions. Compared with wild-type counterparts, Hif-1α KO mice with OIR demonstrated attenuated overproduction of vascular endothelial growth factor (VEGF) and intercellular adhesion molecule (ICAM)-1, reduced vascular leakage and alleviated neovascularisation in the retina. Under diabetes conditions, disruption of Hif-1α in Müller cells attenuated the increases of retinal vascular leakage and adherent leucocytes, as well as the overproduction of VEGF and ICAM-1.

CONCLUSIONS/INTERPRETATION

Müller cell-derived HIF-1α is a key mediator of retinal neovascularisation, vascular leakage and inflammation, the major pathological changes in diabetic retinopathy. Müller cell-derived HIF-1α is therefore a promising therapeutic target for diabetic retinopathy.

Efficacy of statin pretreatment for the prevention of contrast-induced nephropathy: a meta-analysis of randomised controlled trials

Contrast-induced nephropathy (CIN) is a common cause of acute kidney injury. Whether additional benefits can be achieved with the use of statin in decreasing the risk of CIN remains undetermined. The purpose of this meta-analysis is to evaluate the effects of statin pretreatment for the prevention of CIN. PubMed, MEDLINE, Web of Science, EMBASE and EBM Reviews databases were searched for randomised controlled trials comparing statin pretreatment with non-statin pretreatment for the prevention of CIN. Two reviewers independently assessed studies and performed data extraction. Risk ratio (RR) or weighted mean differences (WMD) with 95% confidence intervals (CI) were calculated using random-effects models. Four trials with 751 subjects were included. Pooled analyses showed that the incidence of CIN was not significantly lower in statin pretreatment group, as compared with control group (RR = 0.76, 95% CI 0.44-1.29, p = 0.30). Similarly, none of 276 patients in statin pretreatment group needed renal replacement therapy (RRT), which was not significantly less than 2 of 275 patients assigned to control group during 1-month follow up (RR = 0.33, 95% CI 0.03-3.17, p = 0.34). Moreover, statin pretreatment was associated with mild reduction of serum creatinine (SCr) (WMD = -0.06 mg/dl, 95% CI -0.12 to 0.00 mg/dl, p = 0.05). The current cumulative evidence suggests that statin pretreatment may neither prevent CIN nor reduce the need for RRT. However, it may slightly decrease the level of SCr.

A peptide aldehyde microarray for high-throughput profiling of cellular events

Microarrays provide exciting opportunities in the field of large-scale proteomics. With the aim to elucidate enzymatic activity and profiles within native biological samples, we developed a microarray comprising a focused positional-scanning library of enzyme inhibitors. The library was diversified across P(1)-P(4) positions, creating 270 different inhibitor sublibraries which were immobilized onto avidin slides. The peptide aldehyde-based small-molecule microarray (SMM) specifically targeted cysteine proteases, thereby enabling large-scale functional assessment of this subgroup of proteases, within fluorescently labeled samples, including pure proteins, cellular lysates, and infected samples. The arrays were shown to elicit binding fingerprints consistent with those of model proteins, specifically caspases and purified cysteine proteases from parasites (rhodesein and cruzain). When tested against lysates from apoptotic Hela and red blood cells infected with Plasmodium falciparum, clear signatures were obtained that were readily attributable to the activity of constituent proteases within these samples. Characteristic binding profiles were further able to distinguish various stages of the parasite infection in erythrocyte lysates. By converting one of our brightest microarray hits into a probe, putative protein markers were identified and pulled down from within apoptotic Hela lysates, demonstrating the potential of target validation and discovery. Taken together, these results demonstrate the utility of targeted SMMs in dissecting cellular biology in complex proteomic samples.

Small molecule microarrays: the first decade and beyond

Molecular Bits and Chips: Profiling and discovering the next generation of small molecule ligands.