Intravitreal Bevacizumab Injection Attenuates Diabetic Retinopathy in Adult Rats with Experimentally Induced Diabetes in the Early Stage

Improved Melatonin Delivery by a Size-Controlled Polydopamine Nanoformulation Attenuates Preclinical Diabetic Retinopathy

Oxidative stress, reactive oxygen species generation, and overexpression of VEGF are signatory events in diabetic retinopathy. The downregulation of VEGF and anti-inflammatory action pave the way for diabetic retinopathy (DR) therapy. In that, lower absorption kinetics of melatonin limits its immense therapeutic potential. Hence, we have demonstrated a reverse microemulsion method to synthesize melatonin-loaded polydopamine nanoparticles to replenish both at a single platform with an improved melatonin delivery profile. The study has evaluated in vitro and in vivo protection efficiency of biocompatible melatonin-loaded polydopamine nanoparticles (MPDANPs). The protection mechanism was explained by downregulation of VEGF, CASPASE3, and PKCδ against high-glucose/streptozotocin (STZ)-induced insults, in vitro and in vivo. The anti-inflammatory and antiangiogenic effect and potential of MPDANPs to enhance melatonin in vivo stability with prolonged circulation time have proved MPDANPs as a potential therapeutic candidate in DR management. The DR therapeutic potential of MPDANPs has been arbitrated by improving the bioavailability of melatonin and inhibition of VEGF-PKCδ crosstalk in vivo.

In Situ Liquid Crystal Gel as a Promising Strategy for Improving Ocular Administration of Dexamethasone: Preparation, Characterization, and Evaluation

The purpose of this study was to design an in situ liquid crystal gel (ISLG) as an ophthalmic drug delivery system for dexamethasone (DEX) to enhance its eye retention and ocular bioavailability. The in situ liquid crystal gels (ISLGs) were prepared using a phytantriol/PEG400/water (65:30:5, w/w) ternary system. Polarized light microscope (PLM), small-angle X-ray scattering (SAXS), and rheology analysis confirmed that the internal structure of the preparations was Pn3m cubic phase liquid crystal gels with pseudoplastic fluid properties. Meanwhile, in vitro release behavior of the preparations conforms to the Higuchi equation. Corneal penetration experiments showed that compared with DEX sodium phosphate eye drops, DEX-ISLGs(F2) produced a 5.45-fold increase in the P_app value, indicating a significant enhancement of corneal penetration. In addition, in vivo experiments have confirmed that the ISLGs have better biocompatibility and longer retention time in the cornea. Simultaneously, corneal hydration level, eye irritation experiments, and histological observations proved the safety of the preparations. Pharmacokinetic studies have shown that the ISLG could maintain the DEX concentration in aqueous humor for at least 12 h after administration, which significantly improves the bioavailability of the drug. Collectively, these results indicated that ISLG would be a potential drug carrier for the treatment of diabetic retinopathy (DR).

In vivo fluorescence molecular imaging of the vascular endothelial growth factor in rats with early diabetic retinopathy

Anti-vascular endothelial growth factor (anti-VEGF) therapy is effective for reducing the severity level of diabetic retinopathy (DR). However, it is difficult to determine the in vivo spatial and temporal expression of VEGF in the DR retina at an early stage. Here, we report a quantitatively fluorescence molecular imaging and image analysis method by creating a VEGF targeted fluorescence imaging probe, which can potentially detect and predict anti-VEGF treatment response. Moreover, the ex vivo multiscale fluorescence imaging demonstrated the spatial correlation between VEGF relative expression and vascular abnormalities in two and three dimensions. It revealed that VEGF was mainly abnormally expressed at the bifurcation of the microvessels, which advances the knowledge of the DR progression by molecular fluorescence imaging. Our study has the potential to achieve early detection of DR disease, provide more insight into understanding anti-VEGF treatment, and may help stratify patients based on the molecular imaging of retinal VEGF.

Intraocular pressure fluctuation and neurodegeneration in the diabetic rat retina

BACKGROUND AND PURPOSE

Early retinal neurodegeneration occurs as one of the complications of diabetes even before clinically detectable diabetic vascular retinopathy. The pathogenesis of retinal diabetic neuropathy is still not well understood. We investigated the serial changes or fluctuations in intraocular pressure (IOP) and examined their roles in the pathogenesis of neuronal degeneration in diabetic retina.

EXPERIMENTAL APPROACH

Male Sprague Dawley rats with streptozotocin-induced diabetes were treated with ophthalmic preparations of brinzolamide, latanoprost, both drugs (combined treatment) or saline for 8 weeks. IOP was measured daily under general anaesthesia using a rebound tonometer. Antegrade axoplasmic flow in the optic nerve was assessed with a fluorescent substrate. Immunohistochemical staining, TUNEL assays and western blots were also used.

KEY RESULTS

The fluctuation of IOP was higher in the diabetes group than in the normal control or the combined treatment group. Diabetes-induced apoptosis of retinal ganglion cells was decreased by combined treatment. Increased expression of glial fibrillary acidic protein or Iba-1 in the retina or optic nerve head, induced by diabetes, was attenuated only by the combined treatment. Intercellular adhesion molecule-1 was increased in diabetic rats but not in the combined treatment group. Diabetes-induced loss of antegrade axoplasmic transport was partially relieved with combined treatment.

CONCLUSION AND IMPLICATIONS

Elevated IOP fluctuations seemed to be associated with the gliosis, neuroinflammation, and neurodegeneration induced by diabetes. The loss of retinal ganglion cells might be relieved by IOP-lowering medication. The improvement of unstable perfusion pressure could play a role in neuroprotection in the diabetic retina.

Effects of Intravitreal Bevacizumab Therapy in Patients with Proliferative Diabetic Retinopathy

INTRODUCTION

Diabetes mellitus (DM) stands out as one of the chronic diseases with the highest morbidity and mortality rates worldwide. Among the many complications of DM, diabetic retinopathy (DR) is one of the causes of blindness in patients aged between 20 and 64 years. At least 90% of the new cases showed to have the retinal structure and function restored when proper treatment was provided.

AIM

To evaluate the efficacy of the antiangiogenic bevacizumab in the treatment of DR according not only to the clinical laboratory parameters for glycated hemoglobin (HbA1C) and capillary glycemia but also to the ophthalmological parameters for optical coherence tomography (OCT) and best-corrected visual acuity (BCVA).

PATIENTS AND METHODS

A total of 11 individuals were included and followed up for 12 months after 3 administrations of bevacizumab.

RESULTS

Upon associating the ophthalmological and laboratory variables throughout the treatment, no significant alterations could be seen regarding the analyzed variables. However, it was observed that HbA1c values and the total leukocyte count negatively interfered with the treatment response.

CONCLUSION

The current study showed that HbA1c values and the amount of leukocytes negatively interfere with the therapeutic response. Therefore, laboratory analyses of these parameters are recommended for diabetic patients undergoing the above-mentioned treatment.

Gastrodin Ameliorates Motor Learning Deficits Through Preserving Cerebellar Long-Term Depression Pathways in Diabetic Rats

Cognitive dysfunction is a very severe consequence of diabetes, but the underlying causes are still unclear. Recently, the cerebellum was reported to play an important role in learning and memory. Since long-term depression (LTD) is a primary cellular mechanism for cerebellar motor learning, we aimed to explore the role of cerebellar LTD pathways in diabetic rats and the therapeutic effect of gastrodin. Diabetes was induced by a single injection of streptozotocin into adult Sprague-Dawley rats. Motor learning ability was assessed by a beam walk test. Pathological changes of the cerebellum were assessed by Hematoxylin-Eosin (HE) and Nissl staining. Cellular apoptosis was assessed by anti-caspase-3 immunostaining. Protein expression levels of LTD pathway-related factors, including GluR2, protein kinase C (PKC), NR2A, and nNOS, in the cerebellar cortex were evaluated by western blotting and double immunofluorescence. The NO concentration was measured. The cellular degeneration and the apoptosis of Purkinje cells were evident in the cerebellum of diabetic rats. Protein expression levels of GluR2 (NC9W: 1.26 ± 0.12; DM9W + S: 0.81 ± 0.07), PKC (NC9W: 1.66 ± 0.10; DM9W + S: 0.58 ± 0.19), NR2A (NC9W: 1.40 ± 0.05; DM9W + S: 0.63 ± 0.06), nNOS (NC9W: 1.26 ± 0.12; DM9W + S: 0.68 ± 0.04), and NO (NC9W: 135.61 ± 31.91; DM9W + S: 64.06 ± 24.01) in the cerebellum were significantly decreased in diabetic rats. Following gastrodin intervention, the outcome of motor learning ability was significantly improved (NC9W: 6.70 ± 3.31; DM9W + S: 20.47 ± 9.43; DM9W + G: 16.04 ± 7.10). In addition, degeneration and apoptosis were ameliorated, and this was coupled with the elevation of the protein expression of the abovementioned biomarkers. Arising from the above, we concluded that gastrodin may contribute to the improvement of motor learning by protecting the LTD pathways in Purkinje cells.

Astragalus root extract inhibits retinal cell apoptosis and repairs damaged retinal neovascularization in retinopathy of prematurity

Since the functions of Astragalus root extract in retinopathy remain to be unraveled, this study is performed to elucidate whether Astragalus root extract functions in retinal cell apoptosis and angiogenesis in retinopathy of prematurity (ROP). Newborn mice were selected for establishing mice models of oxygen-induced retinopathy (OIR), which were treated with high-, medium- or low-Astragalus root extract. Evans Blue (EB) was perfused to detect the blood retinal barrier. Additionally, the vascular morphology, number of endothelial cell nuclei of neovascularization, proliferation of blood vessels, ultrastructural changes were determined via a series of assays. Moreover, levels of reactive oxygen species (ROS), expression of other factors such as VEGF, PEDF, IGF-1, HIF-1α, Bax, Bcl-2, eNOS, nNOS, and iNOS were detected. Astragalus root extract was found to protect blood-retinal barrier in the OIR model mice through repairing the structure and morphology of retina, inhibiting ROS production, retinal cell apoptosis, as well as improving retinal vascular angiogenesis. Astragalus root extract was also found to decrease VEGF and HIF-1α expression, but enhance PEDF and IGF-1 expression in the OIR model mice, thereby protecting retinas in ROP. This study highlights that Astragalus root extract is able to suppress retinal cell apoptosis and repair damaged retinal neovascularization in ROP, which provides basis for ROP therapy.

Potential antiedematous effects of intravitreous anti-VEGF, unrelated to VEGF neutralization

The intravitreous injection of therapeutic proteins that neutralize vascular endothelial growth factor (VEGF) family members is efficient to reduce macular edema associated with wet age-related macular degeneration (AMD), retinal vein occlusion (RVO) and diabetic retinopathy (DR). It has revolutionized the visual prognosis of patients with macular edema. The antiedematous effect is dependent on an intravitreous dose of drug, which varies between patients and requires frequent and repeated injections to maintain its effects. At the time when optimizing the duration of anti-VEGF effects is a major challenge, understanding how anti-VEGF reduces macular edema is crucial. We discuss herein how anti-VEGF exerts antiedematous effects and raise the hypothesis that mechanisms, unrelated to VEGF neutralization, might have been underestimated.