Effect of ofloxacin and netilmicin on human corneal and conjunctival cells in vitro

Effects of Ophthalmic Medications on Conjunctival Goblet Cell Density in New Zealand White Rabbits

Introduction

The conjunctiva contains numerous specialized cells called conjunctival goblet cells (CGCs). The topical application of specific eye drops to the ocular surface has conclusively been linked to cause a reduction in CGCs, a condition which has been associated with dry eye and other ocular surface disorders. The purpose of this study was to assess if the use of benzalkonium chloride (BAK) as a preservative in common ophthalmic medications affects CGCs' density in New Zealand white (NZW) rabbit conjunctivas.

Methods

Data from seven preclinical studies conducted between March 2016 and April 2021 were analyzed, involving 146 male NZW rabbits aged 2 to 3 months. Prior to study participation, rabbits underwent a 7-day quarantine period in individual housing, during which their general health was monitored. Rabbits had ad libitum access to water and food, with intake data recorded. Comprehensive ophthalmological examinations were performed on all eyes prior to and throughout the studies. The density of corneal endothelial cells was specifically assessed using AB/PAS staining and quantified with a high-power (40X) field objective (ocular 18 × 22), expressed as a percentage relative to epithelial cells.

Results

No statistically significant differences were found between the with-BAK group and without-BAK group. The mean density in the 30-day group presented a statistically significant higher density than the >30-day group (p = 0.005). Analysis of the treatment revealed that antibiotic/steroid combination group had a higher average number of CGCs compared to both the antihistaminic group (p = 0.004) and hypotensive agent group (p = 0.047).

Conclusion

Exposure to BAK-preserved medications for 30 days results in a higher density of CGCs compared to prolonged exposure to BAK-preserved medications exceeding 30 days. The pharmacological effects and associated cellular damage induced by BAK vary depending on the specific medication with which it is combined.

Short-Term Use of Dexamethasone/Netilmicin Fixed Combination in Controlling Ocular Inflammation After Uncomplicated Cataract Surgery

Purpose

To evaluate the short-term anti-inflammatory effect of dexamethasone/netilmicin fixed combination in the management of ocular inflammation after cataract surgery.

Patients and Methods

Open-label, randomized, active-controlled, clinical study conducted in 6 sites in Italy; 238 patients were randomized 2:1 to dexamethasone/netilmicin (dexa/net, n=158) or betamethasone/chloramphenicol (beta/chl, n=80). Treatment started the day of surgery and continued 4 times daily for 7 days. The primary efficacy parameter was the anterior chamber (AC) flare. The percentage of patients displaying none or mild (ie, only barely detectable) AC flare was defined as “efficacy rate”, whereas the percentage of patients showing a decrease of AC flare score from baseline was defined as “percentage of responders”. Additional parameters evaluated were AC cells, conjunctival hyperaemia, corneal and lid oedema, symptoms of ocular discomfort, visual acuity, and intraocular pressure. Dexa/net was considered effective if the efficacy rate was not inferior (by means of 97.5% confidence interval) to that of beta/chl.

Results

After 7 days of treatment, no AC flare was observed in 92.8% (dexa/net) and 92.3% (beta/chl) of patients, whereas no AC cells were observed in 91.5% (dexa/net) and 93.6% (beta/chl) of patients, respectively. The “efficacy rate” was 100% in both groups, whereas the “percentage of responders” was 94.1% in the dexa/net and 93.6% in the beta/chl group. The p-value to reject the null hypothesis of inferiority was <0.001. Other efficacy parameters confirmed both treatments as highly effective, despite their difference in steroid content (2 mg/mL for beta/chl vs 1 mg/mL for dexa/net). IOP and visual acuity at the end of the study were comparable. Two cases of allergic conjunctivitis were considered adverse events and were both related to dexa/net.

Conclusion

Short-term use of dexa/net fixed combination is safe and effective in the control of post-operative inflammation following uncomplicated cataract surgery.

Dexamethasone/Netilmicin Eye Drops and Eye Gel for the Treatment of Ocular Inflammation After Micro-Incisional Vitreoretinal Surgery

PURPOSE

To evaluate the effect of dexamethasone/netilmicin (dexa/net) fixed combination in the treatment of ocular inflammation after sutureless micro-incisional vitreoretinal surgery (MIVS).

PATIENTS AND METHODS

This multicenter, open, randomized, active-controlled, parallel-group, clinical trial was run in 6 sites in Italy. Treatment started the day of surgery and continued 4 times daily for 14 days. Patients were 1:1 randomized to dexa/net (eyedrops solution and eye gel) or dexamethasone/tobramycin (dexa/tobra) eyedrops suspension and ointment. Viscous formulations (gel or ointment) were used alone during the early post-operative phase; afterwards, a combination of eye drops during daytime and viscous formulations at bedtime was adopted. The primary efficacy parameter evaluated was bulbar conjunctival hyperemia. Additional efficacy and safety parameters (palpebral conjunctival hyperemia, anterior chamber flare and cells, symptoms of ocular discomfort and ocular tolerance, adverse events and intraocular pressure) were also evaluated. Control visits were performed at day 1, day 4 and day 14 after surgery; the endpoint of the study was set at 14±2 days after surgery.

RESULTS

A complete resolution of bulbar conjunctiva hyperaemia at the study end point was reached in 92.9% of patients treated with dexa/net and 75.0% of those treated with dexa/tobra (p=0.02, Fisher's exact test). No differences were observed between treatments for other efficacy parameters. Statistically significant differences in favour of dexa/net (p< 0.0001, ANOVA) were observed for most of subjective tolerance variables examined (blurred vision, foreign body sensation, stickiness, burning) starting day 1 after surgery when only the viscous formulations were used. No increase in intraocular pressure or adverse events was observed during the study.

CONCLUSION

The combination dexa/net is safe and effective in the treatment of post-operative inflammation following sutureless MIVS. In particular, the use of eye gel formulation is characterized by a great tolerability.

[Study of common cytotoxicity of aminoglycoside and fluoroquinolone antibiotics in cell cultures]

The aim of the study was to identify the overall cytotoxicity of aminoglycosides netilmicin and tobramycin, and fluoroquinolone ciprofloxacin.

MATERIAL AND METHODS

We used three types of the cells: constantly transformed cell line CHO-K1, normal human skin fibroblasts and cells of normal human conjunctiva Clone 1-5C-4. Antibiotics activity was detected by their influence on cell viability. Quantitative and qualitative methods of evaluation have used to determine viability of the cells (quantitative assessment: a method of cloning cells and colorimetric method for assessing cell proliferation; qualitative assessment: lifetime visual observation under an inverted microscope for morphological status of cells in culture with photofixing).

RESULTS

The most toxic effect for all types of the cells was shown in tobramycin. The least degree of toxicity for all types of the cells was determined in netilmicin.

CONCLUSION

Studied antibiotics exert a cytotoxic effect in vitro and differ in their cytotoxic potential.

Netilmicin/dexamethasone fixed combination in the treatment of conjunctival inflammation

Purpose

To compare the efficacy and safety of 0.1% dexamethasone/0.3% netilmicin (Netildex), with that of 0.1% dexamethasone/0.3% tobramycin (Tobradex) in the treatment of external ocular inflammation requiring antibiotic therapy.

Methods

In this randomized, double-blind study, 139 subjects with conjunctival inflammation associated with signs of ocular infection were treated with Netildex (n = 71) or Tobradex (n = 68) four times daily for 6 days. The primary efficacy analysis was based on the percentage of patients with at least a 50% decrease in conjunctival hyperemia at the endpoint visit (Day 6 [± 1]) with respect to baseline (responder rate). An equivalence margin of 20% was set for this study. A follow-up visit was performed at Day 14 (± 1). Other efficacy parameters were: conjunctival edema, conjunctival discharge, lid hyperemia, lid edema, presence of ocular infection, and symptoms of ocular discomfort. Safety evaluations included intraocular pressure, visual acuity, and adverse events.

Results

At Day 6, a decrease of conjunctival hyperemia was observed in 87.3% and 90.9% of the patients treated with Netildex and Tobradex, respectively. The 95% confidence interval for the difference between groups (−15.3 ÷ 8.0) satisfied the equivalence hypothesis. Subjects treated with Netildex had a better control of lid hyperemia (P = 0.016), tearing (P = 0.001), burning (P = 0.007), and stinging (P = 0.004). No adverse reactions were observed during the study except one case of keratitis in the Tobradex group.

Conclusion

Netildex was as effective and safe as Tobradex in reducing signs and symptoms in patients with conjunctival inflammation when ocular infection was suspected.

Application of a microfluidic chip-based 3D co-culture to test drug sensitivity for individualized treatment of lung cancer

Individualized treatment is a promising clinical strategy for lung cancer, and drug sensitivity testing is fundamental to this scheme. We aimed to develop an effective drug sensitivity test platform to support individualized treatment. We designed a microfluidic chip-based, three-dimensional (3D) co-culture drug sensitivity test platform. A mono-lung cancer cell line, a mixture of lung cancer and stromal cell lines, and cells from fresh lung cancer tissues were cultured in 3D under continuous media supplementation, mimicking the actual tumor microenvironment in vivo. The cells were treated with anti-cancer drugs according to a gradient concentration generator inside the chips to screen the appropriate chemotherapy schemes. We successfully cultured cell lines or primary cells with this device. We also smoothly assayed the sensitivities of different anti-cancer drugs in parallel and accurately screened appropriate-dose, single and combined-drug chemotherapy schemes for eight patients. Our microfluidic device is a simple, reliable, and high-throughput platform to test drug sensitivity. It would be possible for chemotherapists to screen the appropriate chemotherapy schemes to guide individualized treatment in lung cancer.

A new eye gel containing sodium hyaluronate and xanthan gum for the management of post-traumatic corneal abrasions

PURPOSE

The aim of this study was to investigate the effects of an ophthalmic gel containing sodium hyaluronate and xanthan gum in addition to the antibiotic netilmicin in the management of traumatic corneal abrasions.

PATIENTS AND METHODS

PATIENTS WITH TRAUMATIC CORNEAL ABRASIONS WERE RANDOMLY TREATED AS FOLLOWS: Group A (n = 20) with an occlusive patching for 12 hours plus one drop of an eye gel containing 0.15% sodium hyaluronate, 1% xanthan gum and 0.3% netilmicin qid for 5 days; and Group B (n = 20) with an occlusive patching for 2-3 days plus one application of 0.3% netilmicin ophthalmic ointment qid for 5 days. All patients were evaluated after the third and seventh day by slit-lamp examination, fluorescein staining, and corneal defect photograph in order to assess corneal re-epithelialization. Conjunctival hyperaemia, lid oedema, subjective symptoms of discomfort, and conjunctival swabs were also evaluated.

RESULTS

No statistically significant difference was observed between the groups in terms of the extent of corneal healing after 3 days of treatment. Both treatments were also highly effective in decreasing the erosion score and the conjunctival hyperemia (P < 0.0001, P < 0.005, respectively) without any significant difference between the two types of treatment. Subjective symptoms of discomfort and conjunctival swabs were also evaluated.

CONCLUSION

In the management of traumatic corneal abrasions, the administration of an eye gel containing sodium hyaluronate and xanthan gum is able to reduce the length of occlusive patching. In addition, the presence of netilmicin guarantees good antibiotic prophylaxis during the wound repair process.

Comparison of gene expression profiles of conjunctival cell lines with primary cultured conjunctival epithelial cells and human conjunctival tissue

Human conjunctival cell lines are useful tools for modeling ocular surface disease and evaluation of ocular drugs and cosmetics. However, gene expression in these cells may not be comparable to primary cultured cells, raising doubts that they could be used as a substitute. We aimed to ascertain the similarities of global gene expression between commonly used cell lines and primary cells using a microarray approach. The Affymetrix U133A chip (>22,000 genes) was used to investigate conjunctival tissue (CT), primary conjunctival epithelial cells (PCEC), two conjunctival epithelial cell lines (IOBA-NHC and ChWK), and HCEC-T, a human corneal epithelial cell line (control). Using principal component analysis, the PCEC profile was clustered more closely to conjunctival tissue than either of the two cell lines. Certain extracellular matrix genes were differentially upregulated in CT compared to PCEC, suggesting presence of fibroblasts in addition to epithelial cells in CT. Overall, 67.3% (95% CI: 66.7-67.9) of transcripts in IOBA-NHC were within 1.5-fold of the corresponding transcripts in PCEC, but only 62.2% (95% CI: 61.5-62.9) in the case of ChWK. In HCEC-T, the proportion was only 58.8% (95% CI 58.1-59.4), suggesting less resemblance to PCEC than the conjunctival epithelial cell lines. The IOBA-NHC profile was more similar to PCEC than ChWK, for all genes and genes concerned with membrane association, communication, development, and regulation of metabolism, especially protein and nucleic acid metabolism. The correlation of normalized gene expression levels was high between either the IOBA-NHC or ChWK and PCEC for genes concerned with cell defense, viral life cycle, antigen presentation, antioxidation, or ubiquitin ligation. In order to evaluate the functional significance of the altered gene expression in IOBA-NHC cells, we evaluated a few proteins important for epithelial differentiation or defense, corresponding to the transcripts for S100A9, TGM2, and TLR4. Protein levels of S100A9 and TGM2 were indeed raised, and TLR4 decreased, in IOBA-NHC compared to PCEC. Gene expression in conjunctival cell lines differs from primary cells, but the profile varies according to functional gene categories. Depending on the methodology of proposed studies, if there is limited availability of PCEC, NHC-IOBA may be more suitable than ChWK, but even then, epithelial differentiation and innate immunity functions in NHC-IOBA may differ from primary cells.

In Vitro Effects of Fluoroquinolone and Aminoglycoside Antibiotics on Human Keratocytes

PURPOSE

The purpose of this study was to assess the cytotoxic effects of the fluoquinolone ofloxacin and the aminoglycoside netilmicin on stromal human keratocytes in vitro.

METHODS

Cultured human keratocytes were exposed to various concentrations of ofloxacin or netilmicin (0.16-5.0 mg/mL). Both cell proliferation (MTT assay) and cell morphology (phase-contrast microscopy) were evaluated after 1, 4, 12, and 24 hours of incubation. Measurement of annexin V binding performed in association with the dye exclusion test using propidium iodide (PI) was also performed by FACS analysis after 4 hours of exposure.

RESULTS

Both antimicrobials induced dose- and time-dependent morphologic changes in keratocytes, yet the effects of netilmicin were minimal. After 24 hours of exposure, both drugs induced a dose-dependent inhibition of cell proliferation; however, ofloxacin demonstrated significantly more toxic effects than netilmicin (t test for ED50 values, P < 0.0001). Statistical differences between 2 antibiotics start at concentrations above 1.25 mg/mL (ANOVA with post-hoc test, P < 0.01). Expression of the apoptotic marker annexin V was unaffected by antibiotic exposure, whereas the uptake of the necrotic marker PI was increased by ofloxacin (5 mg/mL) but not by netilmicin (ofloxacin versus netilmicin, ANOVA, P < 0.05).

CONCLUSIONS

Relative effects of aminoglycosides and fluoroquinolones on stromal keratocytes appear to be different: netilmicin was shown to be significantly less toxic than ofloxacin. This finding is particularly relevant in deciding the optimal antibiotic to be applied in clinical situations in which the epithelium is absent or compromised, as after photorefractive keratectomy, alkali burns, or ulcerative keratitis.

Effects of Poly-L-arginine on the Permeation of Hydrophilic Compounds through Surface Ocular Tissues

We investigated whether poly-L-arginine (PLA) could improve permeation of the hydrophilic compounds, FITC-labeled dextran (MW 3800, FD-4) and pyridoxamine, through ocular surface tissues. Samples of cornea, conjunctiva, or conjunctiva/sclera composite from Japanese white rabbits were mounted in Ussing chambers to measure FD-4 and pyridoxamine permeation and transepithelial electric resistance (TEER). The integrity and viability of the conjunctiva were assessed by chronological TEER monitoring and MTT assay, respectively. The permeability coefficient (Papp) of FD-4 in the cornea, conjunctiva, and conjunctiva/sclera composite was increased by the addition of PLA (MW 38 kDa, PLA (50) at 0.1 mg/ml by 6.81-, 9.78-, and 7.91-fold, respectively. The Papp of pyridoxamine was also increased in the presence of PLA (50) by 7.98-, 4.67-, 8.31-fold, respectively. A corresponding reduction in TEER was observed in all tissues. However, the reduced TEER in the case of the conjunctiva had recovered to ca. 70% 120 min after replacing the mucosal fluid with fresh bicarbonated Ringer's solution. MTT assay results indicated that treatment of the conjunctiva with 0.1 mg/ml PLA (50) did not change the production of formazan compared to that without PLA (50), indicating that the conjunctival viability is not significantly affected by PLA (50). Our findings suggest that PLA may be useful in promoting the ocular delivery of hydrophilic drugs without producing significant epithelial damage.

Dexamethasone-netilmicin: a new ophthalmic steroid-antibiotic combination. Efficacy and safety after cataract surgery

PURPOSE

The purpose of this study was to evaluate both efficacy and safety of a new ophthalmic steroid-antibiotic fixed combination containing dexamethasone and netilmicin in the postsurgical management of cataract surgery.

METHODS

In total, 223 patients were randomly treated with dexamethasone 1 mg/ml plus netilmicin 3 mg/ml (n=148), or dexamethasone 1 mg/ml plus tobramycin 3 mg/ml (n=75, TOBRADEX) four times in a day for 7+/-1 days starting immediately after surgery. Efficacy (anterior chamber (AC) inflammation, conjunctival hyperaemia, corneal and lid oedema, ocular infection, pain, photophobia and tearing) and safety (burning, stinging, blurred vision, intraocular pressure, and visual acuity) were analysed in the operated eye after 1 and 7+/-1 days. A follow-up visit was performed at day 14+/-2. The extent of AC inflammation, measured by slit-lamp according to a standard scoring system, was used as primary efficacy parameter.

RESULTS

At the primary end point (day 7) both fixed combinations were equally effective in reducing postoperative inflammation. The safety profile of the dexamethasone/netilmicin combination was excellent with no evidence of poor local tolerance or adverse reaction.

CONCLUSIONS

A new fixed combination of dexamethasone and netilmicin was effective and safe in controlling ocular inflammation after cataract surgery.

In Vivo Toxicity of Netilmicin and Ofloxacin on Intact and Mechanically Damaged Eyes of Rabbit

PURPOSE

To evaluate the in vivo toxicity of netilmicin and ofloxacin using both normal and mechanically damaged eyes of rabbit.

METHODS

Male albino New Zealand rabbits were given either 0.3% netilmicin, 0.3% ofloxacin, or 0.9% sodium chloride solution by topical instillation (50 microL) into the conjunctival sac 6 times daily for 5 days. In some animals a 6-mm-diameter epithelial wound was mechanically made to the center of the cornea. Ocular toxicity on normal eyes was evaluated by impression cytology of the conjunctiva, histology of the entire globes, and scanning electron microscopy (SEM) of the cornea. Analysis of toxicity and reepithelialization on wounded corneas was evaluated by SEM with observations being made 48 and 72 hours after induction of the wound.

RESULTS

Cytologic, histopathologic, and SEM analyses of normal healthy eyes following netilmicin treatment revealed no signs of toxicity, whereas those treated with ofloxacin revealed alterations in the cornea (stromal swelling) and conjunctiva (infiltration of polymorphonuclear cells) with reduced goblet cell numbers. Wounded corneas treated with netilmicin exhibited normal morphology and reepithelialization, whereas the administration of ofloxacin resulted in disordered cellular organisation and slower rates of epithelial recovery.

CONCLUSIONS

Netilmicin, an antibacterial aminoglycoside, is well tolerated even in an experimental wound-healing model where the integrity of the ocular surface is compromised, whereas ofloxacin, a fluoroquinolone, appears to provoke an inflammatory response in the normal eye and a clear alteration of reepithelialization in the wounded eye. These findings suggest that netilmicin may offer a superior toxicological profile in both normal eyes and clinical situations where the integrity of the ocular epithelium is suspect.