Diabetes mellitus is a widespread metabolic disorder, and long-term hyperglycemia in diabetics leads to diabetic keratopathy. In the present study, we used a shotgun liquid chromatography/mass spectrometry-based global proteomic approach using the cornea of streptozotocin-induced diabetic (STZ) rats to examine the mechanisms of delayed corneal wound healing in diabetic keratopathy. Applying a label-free quantitation method based on spectral counting, we identified 188 proteins that showed expression changes of >2.0-fold in the cornea of STZ rats. In particular, the level of lumican expression in the cornea of STZ rats was higher than that of the normal rats. In the cornea of the normal rat, the expression level of lumican was elevated during the wound healing process, and it returned to the same expression level as before cornea injury after the wound was healed completely. On the other hand, a high expression level of lumican in the cornea of STZ rats was still maintained even after the wound was healed completely. In addition, adhesion deficiency in corneal basal cells and Bowman’s membrane was observed in the STZ rat. Thus, abnormally overexpressed lumican may lead to adhesion deficiency in the cornea of STZ rats.

We designed an intravitreal injection formulation containing lanosterol nanoparticles (LAN-NPs) via the bead mill method and evaluated the therapeutic effect of LAN-NPs on lens structure collapse and opacification using two rat cataract models (SCR-N, rats with slight lens structure collapse; SCR-C, rats with the combination of a remarkable lens structure collapse and opacification). The particle size of lanosterol in the LAN-NPs was around 50–400 nm. A single injection of LAN-NPs (0.5%) supplied lanosterol into the lens for 48 h, and no irritation or muddiness was observed following repeated injections of LAN-NPs for 6 weeks (once every 2 days). Moreover, LAN-NPs repaired the slight collapse of the lens structure in SCR-N. Although the remarkable changes in the lens structure of SCR-C were not repaired by LAN-NP, the onset of opacification was delayed. In addition, the increase of cataract-related factors (Ca²⁺ contents, nitric oxide levels, lipid peroxidation and calpain activity levels) in the lenses of SCR-C was attenuated by the repeated injection of LAN-NPs. It is possible that a deficiency of lanosterol promotes the production of oxidative stress. In conclusion, it is difficult to improve serious structural collapse with posterior movement of the lens nucleus with a supplement of lanosterol via LAN-NPs. However, the intravitreal injection of LAN-NPs was found to repair the space and structural collapse in the early stages in the lenses.

Retinopathy leads to irreparable vision loss via capillary closure and areas of nonperfusion. However, the current instillation systems do not allow a sufficient amount of drug required to treat retinopathy to reach the posterior segment (retina); therefore, a new formulation targeting the posterior segment is expected as therapy for retinopathy. We prepared ophthalmic formulations containing nilvadipine nanoparticles (NIL_nano), and demonstrated whether the instillation of NIL_nano can prevent retinal dysfunction in rats injected with excessive streptozotocin (STZ rats) in this study. NIL_nano (mean particle size, 77 nm) was prepared by wet bead mill treatment, with the inclusion of various additives (2-hydroxypropyl-β-cyclodextrin, benzalkonium chloride, d-mannitol, and methylcellulose). Retinal dysfunction was observable two weeks after rats received intraperitoneal injections of streptozotocin (100 mg/kg × 2, consecutive days, STZ rat). Changes in retinal function were evaluated by electroretinogram (ERG) and immunological methods. The retinal thickness, measured as the distance between the ganglion cell layer and the distal border of the outer nuclear layer, increased two weeks after the injection of streptozotocin, resulting in decreases in the levels of a-waves, b-waves, and oscillatory potential amplitudes in ERG of rats. The instillation of NIL_nano allowed the topical supplement of nilvadipine into the retina, and repeated instillation of NIL_nano (2 times/day) attenuated the retinal disorders led by the excessive streptozotocin. In conclusion, we found that retinal dysfunction in rats injected with streptozotocin can be prevented by the NIL_nano instillation. These results are useful in further studies aimed at the therapeutic treatment of retinopathy.

We previously prepared ophthalmic formulations containing cilostazol (CLZ) nanoparticles by bead mill methods (CLZ_nano), and found that instillation of CLZ_nano into rat eyes supplies CLZ into the retina. In this study, we investigated changes in the electroretinograms (ERG) of streptozotocin-induced diabetic rats (STZ rats), a model of diabetes mellitus. In addition, we demonstrated that dispersions containing CLZ nanoparticles attenuate changes in the ERG of STZ rats. The instillation of CLZ_nano had no effect on body weight or plasma glucose and insulin levels. Furthermore, no corneal toxicity was observed in the in vivo study using STZ rats. The a-wave and b-wave levels in addition to oscillatory potentials (OP) amplitude decreased in STZ rats two weeks after the injection of streptozotocin, with the instillation of CLZ_nano attenuating these decreases. In addition, the level of vascular endothelial growth factor (VEGF) in the retinas of STZ rats was 9.26-fold higher than in in normal rats, with this increase also prevented by the instillation of CLZ_nano Thus, we have found that a-wave and b-wave levels in addition to OP amplitude are decreased in rats following the injection of excessive streptozotocin. Furthermore, the retinal disorders associated with diabetes mellitus are attenuated by the instillation of CLZ_nano. These findings provide significant information that can be used to design further studies aimed at developing anti-diabetic retinopathy drugs.

We attempted to prepare ophthalmic in situ gel formulations containing lanosterol (Lan) nanoparticles (LA-NPs/ISG) and investigated the characteristics, delivery pathway into the lens, and anti-cataract effects of LA-NPs/ISG using SCR-N (rats with slight lens structure collapse) and SCR-C (rats with a combination of remarkable lens structure collapse and opacification). LA-NPs/ISG was prepared by bead milling of the dispersions containing 0.5% Lan powder, 5% 2-hydroxypropyl-β-cyclodextrin, 0.5% methylcellulose, 0.005% benzalkonium chloride, and 0.5% mannitol. The particle size distribution of Lan was 60–250 nm. The LA-NPs/ISG was gelled at 37 °C, and the LA-NPs/ISG was taken into the cornea by energy-dependent endocytosis and then released to the intraocular side. In addition, the Lan contents in the lenses of both SCR-N and SCR-C were increased by the repetitive instillation of LA-NPs/ISG (twice per day). The space and structure collapse in the lens of SCR-N with aging was attenuated by the instillation of LA-NPs/ISG. Moreover, the repetitive instillation of LA-NPs/ISG attenuated the changes in cataract-related factors (the enhancement of nitric oxide levels, calpain activity, lipid peroxidation levels, Ca²⁺ contents, and the decrease of Ca²⁺-ATPase activity) in the lenses of SCR-C, and the repetitive instillation of LA-NPs/ISG delayed the onset of opacification in the SCR-C. It is possible that the LA-NPs/ISG is useful in maintaining lens homeostasis.

The prevalence of nuclear cataracts was observed to be significantly higher among residents of tropical and subtropical regions compared to those of temperate and subarctic regions. We hypothesized that elevated environmental temperatures may pose a risk of nuclear cataract development. The results of our in silico simulation revealed that in temperate and tropical regions, the human lens temperature ranges from 35.0 °C to 37.5 °C depending on the environmental temperature. The medium temperature changes during the replacement regularly in the cell culture experiment were carefully monitored using a sensor connected to a thermometer and showed a decrease of 1.9 °C, 3.0 °C, 1.7 °C, and 0.1 °C, after 5 min when setting the temperature of the heat plate device at 35.0 °C, 37.5 °C, 40.0 °C, and 42.5 °C, respectively. In the newly created immortalized human lens epithelial cell line clone NY2 (iHLEC-NY2), the amounts of RNA synthesis of αA crystallin, protein expression, and amyloid β (Aβ)1-40 secreted into the medium were increased at the culture temperature of 37.5 °C compared to 35.0 °C. In short-term culture experiments, the secretion of Aβ1-40 observed in cataracts was increased at 37.5 °C compared to 35.0 °C, suggesting that the long-term exposure to a high-temperature environment may increase the risk of cataracts.