The cytotoxic effect of oxybuprocaine on human corneal epithelial cells by inducing cell cycle arrest and mitochondria-dependent apoptosis

Preservative-Free Topical Anesthetic Unit-Dose Eye Drops for the Management of Postoperative Pain Following Photorefractive Keratectomy

INTRODUCTION

Ocular pain is a common complication following photorefractive keratectomy (PRK). The level of patient satisfaction with current pain control strategies is not high. This study aims to assess the efficacy and safety of a novel regimen of preservative-free oxybuprocaine hydrochloride 0.4% unit-dose eye drops for post-PRK pain control.

METHODS

In a contralateral eye study, 144 eyes of 72 patients who underwent bilateral transepithelial PRK (TransPRK) were stratified into experimental and control groups. The experimental group received preservative-free oxybuprocaine hydrochloride 0.4% unit-dose eye drops five times daily postoperatively until complete epithelial healing, while the control group received sodium hyaluronate 0.2% instead. The main outcome measures were pain scores assessed by the verbal rating scale and visual analogue scale (VRS, VAS), the corneal epithelial defect (CED) area, epithelial healing duration evaluated by slit-lamp biomicroscopy and anterior segment optical coherence tomography (AS-OCT), and endothelial cell density (ECD) measured before and 1 month after surgery.

RESULTS

Pain scores assessed by VRS and VAS were significantly lower in the experimental group 8 h after surgery, and 1, 2, and 3 days postoperatively (P < 0.001). The mean CED area showed no significant differences between the two groups at different follow-ups (P value > 0.05). The corneal epithelial healing had a mean duration of 3.32 ± 0.47 days in both studied groups and was parallel in both eyes of each patient. In each group, 49 eyes (68%) and 72 eyes (100%) had a fully epithelialized surface on the third and fourth postoperative days, respectively. No significant changes were observed in the mean ECD 1 month following surgery in both groups (P value > 0.05).

CONCLUSION

Preservative-free oxybuprocaine hydrochloride 0.4% unit-dose eye drops are effective and safe in controlling early postoperative pain following TransPRK. The availability of the single-dose unit preparation can overcome the problem of topical anesthetic abuse.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05733741.

An eye on the Shih Tzu dog: Ophthalmic examination findings and ocular surface diagnostics

OBJECTIVE

To characterize the ocular surface parameters and determine the prevalence of ocular pathology in Shih Tzu dogs.

ANIMAL STUDIED

Fifty Shih Tzu dogs (28 male, 22 female).

PROCEDURES

Each dog underwent a complete ophthalmic examination (recording any pathology) and a series of diagnostics, allowing for a 10 min-interval between tests: intraocular pressure (IOP), blink rate, palpebral fissure length (PFL), corneal tactile sensation (CTS), Schirmer tear test, and nasolacrimal reflex without (STT-1, NL-STT1) and with topical anesthesia (STT-2, NL-STT2), tear ferning, strip meniscometry test (SMT), tear film breakup time (TFBUT), and punctate fluorescein staining (PFS) of the cornea.

RESULTS

Mean ± SD test values were as follows: IOP (17.9 ± 3.7 mmHg), blink rate (2.4 ± 1.4 blinks/min), PFL (23.8 ± 1.8 mm), CTS (1.8 ± 0.7 cm), STT-1 (22.0 ± 5.5 mm/min), NL-STT1 (24.2 ± 4.7 mm/min), STT-2 (16.9 ± 6.5 mm/min), NL-STT2 (18.5 ± 7.5 mm/min), SMT (7.5 ± 3.5 mm/5 s), TFBUT (5.3 ± 2.4 s), tear ferning (1.3 ± 0.7), and PFS (1.6 ± 0.6). PFL was significantly greater in male vs. female Shih Tzus (p< .001). Age was negatively correlated with TFBUT results (r = -0.31, p = .027). Lagophthalmos was observed in 82% eyes. Ocular surface pathology was common, including adnexal abnormalities (100% eyes with caruncular trichiasis and medial lower lid entropion) and corneal opacification (27% pigmentation, 20% fibrosis, 12% neovascularization).

CONCLUSIONS

Qualitative tear film deficiency (low TFBUT), along with several anatomical abnormalities that promote ocular irritation and reduce globe protection, together help explain the concerningly high prevalence of ocular surface disease in the Shih Tzu breed. Prophylactic measures (e.g., medial canthoplasty, topical lubrication) could be considered to improve ocular health in Shih Tzus.

Therapeutic measures for sulfur mustard-induced ocular injury

The use of sulfur mustard (SM) in global terrorism is still a relevant threat to both civilian population and military personnel. Casualties exposed to SM may present mild, moderate or severe acute ocular lesions followed by a complete ocular resolution, chronic lesions or re-emerged ocular pathologies after a latent period. Current treatment for SM-induced ocular injury is based mainly on the clinical manifestation at the different stages of the injury and includes pharmaceutical and surgical interventions. These therapeutic measures are beneficial but not sufficient, and the ocular injury remains a continuous challenge for medical professionals. This review focuses on treatment experience carried out in humans and studied in animal models, for both SM-induced ocular acute injury and late pathology. In general, therapeutic measures are based on clinical features of the ocular injury or on the involvement of specific factors during the ocular injury that point out towards potential treatments. Anti-inflammatory treatments and limbal stem cell transplantation techniques were developed based on the clinical manifestation of the ocular injury. Optional therapies for impaired corneal innervation and endothelium are suggested for future research. Additionally, studies on potential treatments with anti-matrix metalloproteinase (MMP), anti-vascular endothelial growth factor (VEGF) and anti-IL-6 agents are discussed. Consequently, future studies may reveal the potential of additional pharmacological and biological treatments or advanced cellular and molecular biology methods to serve as novel therapeutic measures and techniques for this complicated ocular injury.

Norfloxacin induces apoptosis and necroptosis in human corneal epithelial cells

Norfloxacin (NOR) is applied clinically to treat keratitis. However, NOR has brought severe side-effects for human corneal epithelium (HCEP) due to overdose and potential toxicity. In this study, two in vitro experimental models including monolayer HCEP cells and tissue-engineered human corneal epithelium (TE-HCEP) were used to explore the cytotoxicity and its related mechanisms. The HCEP cells treated with NOR at concentrations from 0.1875 to 3.0 mg/mL displayed abnormal morphology, declined viability, and increased plasma membrane permeability. Moreover, 0.75 mg/mL NOR induced chromatin condensation, S phase arrest, phosphatidylserine externalization, and formation of apoptotic body through activation of caspase-2/-8/-9/-3, downregulation of Bcl-2 and Bcl-xL, upregulation of Bad and Bax, mitochondrial transmembrane potential disruption and release of cytochrome c and apoptosis inducing factor into cytosol, whereas 1.5 mg/mL and 3.0 mg/mL NOR upregulated the expressions of receptor-interacting protein kinase 1 (RIPK1), RIPK3 and mixed lineage kinase domain-like (MLKL) together with inactivation of caspase-2/-8. Furthermore, 0.1875-3.0 mg/mL NOR destroyed the multilayer structure of TE-HCEP model due to a dose-dependent cytotoxicity, which validated the above results. Overall, low-dose (0.1875-0.75 mg/mL) NOR induced apoptosis through mitochondrion-dependent and death receptor-mediated pathways, and high-dose (1.5-3.0 mg/mL) NOR triggered necroptosis via RIPK1-RIPK3-MLKL cascade in HCEP cells.

Phenylephrine induces necroptosis and apoptosis in corneal epithelial cells dose- and time-dependently

In the present study, the toxicity of phenylephrine, a selective α1-adrenergic receptor agonist, in corneal epithelial cells and its underlying mechanisms were investigated using an in vitro model of human corneal epithelial cells (HCEPCs) and an in vivo model of New Zealand white rabbit corneas. The HCEPCs treated with phenylephrine at concentrations from 10% to 0.078125% displayed abnormal morphology, decline of cell viability and elevation of plasma membrane permeability time- and dose-dependently. Moreover, 10%-1.25% phenylephrine induce necrosis characteristics of marginalization and uneven distribution of chromatin through up-regulation of RIPK1, RIPK3 and MLKL along with inactivation of caspase-8 and caspase-2, whereas 0.625% phenylephrine induced condensed chromatin, S phase arrest, phosphatidylserine externalization, DNA fragmentation and apoptotic body formation in the HCECs through activation of caspase-2, -8, -9 and -3 as well as down-regulation of Bcl-2, up-regulation of Bad, ΔΨm disruption and release of cytochrome c and AIF into cytosol. At last, 10% phenylephrine induced destruction of the corneal epithelia and apoptosis of corneal epithelial cells in rabbit corneas. In conclusion, 10% to 1.25% phenylephrine cause necroptosis via RIPK1-RIPK3-MLKL axis and 0.625% phenylephrine induce apoptosis via a mitochondrion-dependent and death receptor-mediated signal pathway in HCEPCs.

Apoptotic effects of norfloxacin on corneal endothelial cells

Norfloxacin, a frequently used ocular antibiotic, might have cytotoxic effect on human corneal endothelial cells (HCECs), subsequently damage the cornea and finally impair human vision. However, the possible mechanisms of cytotoxicity of norfloxacin to HCEC line are unclear. Herein, we investigated the cytotoxicity of norfloxacin and its underlying cellular and molecular mechanisms using in vitro cultured non-transfected HCECs and verified the cytotoxicity with cat corneal endothelium in vivo. In the present study, the cytotoxicity of norfloxacin in the in vitro cultured HCECs was recognized by causing abnormal morphology such as cell shrinkage and detachment from plate bottom, and decline of viability of in vitro cultured HCECs. Then, its cytotoxicity was verified by inducing reduction of cell density and morphological abnormality of in vivo cat corneal endothelial cells. Furthermore, the cytotoxicity of norfloxacin in HCECs was corroborated as apoptosis by elevation of plasma membrane permeability, S phase arrest, phosphatidylserine externalization, DNA fragmentation, and apoptotic body formation in in vitro cultured HCECs and apoptosis-like swollen cells in the in vivo model. Moreover, norfloxacin induced extrinsic death receptor-mediated apoptosis pathway by activating caspase-2/-8/-3 and intrinsic mitochondrion-dependent apoptosis pathway by downregulating anti-apoptotic Bcl-2 and upregulating of pro-apoptotic Bad, which disrupted mitochondrial transmembrane potential, subsequently upregulated cytoplasmic cytochrome c and apoptosis-inducing factor and finally activated caspase-9/-3. Generally, norfloxacin induces HCE cell apoptosis via a death receptor-mediated and mitochondrion-dependent signaling pathway.

Tetracaine induces apoptosis through a mitochondrion-dependent pathway in human corneal stromal cells in vitro

PURPOSE

Tetracaine is a local anesthetic widely used in ocular diagnosis and ophthalmic surgery and may lead to some adverse effects and complications at a clinical dose. To assess the cytotoxicity and molecular toxicity mechanisms of tetracaine, we used human corneal stromal (HCS) cells as an in vitro model to study the effects of tetracaine on HCS cells.

MATERIALS AND METHODS

The cytotoxicity of tetracaine on HCS cells was investigated by examining the changes of cell growth, morphology, viability and cell cycle progressing when HCS cells were treated with tetracaine at concentrations from 10 g/L to 0.078125 g/L. To prove the hypothesis that the cytotoxicity of tetracaine on HCS cells was related with apoptosis induction, we further detected multiple changes in HCS cells, including plasma membrane (PM) permeability, phosphatidylserine (PS) orientation, genomic DNA integrality, and cell ultrastrcuture after treated with tetracaine. Furthermore, the pro-apoptotic signalling pathway induced by tetracaine was explored through detecting the activation of various caspases, the changes of mitochondrial transmembrane potential (MTP), the expression level of Bcl-2 family proteins and the amount of mitochondria-released apoptosis regulating proteins in cytoplasm.

RESULTS

Tetracaine at concentrations above 0.15625 g/L had a dose- and time-dependent cytotoxicity to HCS cells, which resulted cell growth inhibition, proliferation retardation, morphological abnormalities and decreased viability. Meanwhile, we found that the HCS cells treated with tetracaine had typical features associated with apoptosis, including an increase in PM permeability, PS externalization, DNA fragmentation and apoptotic body formation. Tetracaine not only resulted in caspase-3, caspase-8 and caspase-9 activation and disruption of MTP but also downregulated Bcl-2 and Bcl-xL and upregulated Bad and Bax, along with the upregulation of cytoplasmic cytochrome c (Cyt. c) and apoptosis-inducing factor (AIF).

CONCLUSIONS

These results suggested that tetracaine-induced apoptosis might be triggered through Fas death receptors and mediated by Bcl-2 family proteins in the mitochondria-dependent pathway. Our findings identified the cytotoxicity and molecular mechanisms of tetracaine, which could provide a reference value for the safety of this medication and prospective therapeutic interventions in eye clinic.