Isotretinoin Impairs the Secretory Function of Meibomian Gland Via the PPARγ Signaling Pathway

The impact of systemic isotretinoin treatment on the tear film, meibomian glands, and corneal endothelium

PURPOSE

The study aims to investigate changes in tear function, meibomian glands and corneal endothelium in patients receiving systemic isotretinoin therapy.

MATERIALS AND METHODS

This prospective study included 38 eyes from 38 patients (23 females and 15 males) treated with systemic isotretinoin (0.5-1 mg/kg/day) following the diagnosis of acne vulgaris. All patients underwent a comprehensive ophthalmologic examination at baseline, 1st month, and third month of treatment. Subjective complaints were assessed using the Ocular Surface Disease Index (OSDI). Tear functions were evaluated through non-invasive tear break up time (NIBUT) and Schirmer I test. Meibomian gland (MG) changes were examined using meibography. Corneal parameters, including endothelial cell density (ECD), coefficient of variation (CV), the number of cells with a hexagonal shape (6A), average cell area (AVG), and central corneal thickness (CCT) were assessed using non-contact specular microscopy.

RESULTS

The mean age of the patients was 19.29 ± 2.83 years. Ocular surface-related discomfort, measured with OSDI scores, significantly worsened at the third month measurements compared to the pre-treatment values (p < 0.001). In the 1st month of treatment, there was a significant decrease in NIBUT (p < 0.05). No statistically significant difference was found in the Schirmer test results at each visit. According to the 1st and third-month analysis, there was a significant increase in MG loss compared to the pre-treatment period (p < 0.001). ECD, CV, 6 A, AVG measurements at the first and third months showed a significant change compared to the pre-treatment values (p < 0.001). No significant difference was observed in the CCT measurements during the treatment.

CONCLUSION

Systemic isotretinoin disrupted tear stability, caused MG loss, deterioration in corneal endothelium, and led to symptomatic complaints in patients.

Disrupted mitochondrial transcription factor A expression promotes mitochondrial dysfunction and enhances ocular surface inflammation by activating the absent in melanoma 2 inflammasome

PURPOSE

Severe dry eye disease causes ocular surface damage, which is highly associated with mitochondrial dysfunction. Mitochondrial transcription factor A (TFAM) is essential for packaging mitochondrial DNA (mtDNA) and is crucial for maintaining mitochondrial function. Herein, we aimed to explore the effect of a decreased TFAM expression on ocular surface damage.

METHODS

Female C57BL/6 mice were induced ocular surface injury by topical administrating benzalkonium chloride (BAC). Immortalized human corneal epithelial cells (HCECs) were stimulated by tert-butyl hydroperoxide (t-BHP) to create oxidative stress damage. HCECs with TFAM knockdown were established. RNA sequencing was employed to analyze the whole-genome expression. Mitochondrial changes were measured by transmission electron microscopy, Seahorse metabolic flux analysis, mitochondrial membrane potential, and mtDNA copy number. TFAM expression and inflammatory cytokines were determined using RT-qPCR, immunohistochemistry, immunofluorescence, and immunoblotting.

RESULTS

In both the corneas of BAC-treated mice and t-BHP-induced HCECs, we observed impaired TFAM expression, accompanied by mitochondrial structure and function defects. TFAM downregulation in HCECs suppressed mitochondrial respiratory capacity, reduced mtDNA content, induced mtDNA leakage into the cytoplasm, and led to inflammation. RNA sequencing revealed the absent in melanoma 2 (AIM2) inflammasome was activated in the corneas of BAC-treated mice. The AIM2 inflammasome activation was confirmed in TFAM knockdown HCECs. TFAM knockdown in t-BHP-stimulated HCECs aggravated mitochondrial dysfunction and the AIM2 inflammasome activation, thereby further triggering the secretion of inflammatory factors such as interleukin (IL) -1β and IL-18.

CONCLUSIONS

TFAM reduction impaired mitochondrial function, activated AIM2 inflammasome and promoted ocular surface inflammation, revealing an underlying molecular mechanism for ocular surface disorders.

Rho-kinase inhibitor alleviates CD4+T cell mediated corneal graft rejection by modulating its STAT3 and STAT5 activation

Penetrating keratoplasty remains the most common treatment to restore vision for corneal diseases. Immune rejection after corneal transplantation is one of the major causes of graft failure. In recent years, Rho-associated protein kinase (ROCK) inhibitors have been found to be associated with the activation of the STATs pathway and are widely studied in autoimmune diseases. Therefore, it may be possible that the ROCK inhibitors also participate in the local and systemic immune regulation in corneal transplantation through activation of the STATs pathway and affect the CD4+ T cell differentiation. This study aimed to explore the role of ROCK-STATs pathway in the occurrence of immune rejection in corneal transplantation by applying Y27632, a ROCK inhibitor, to the recipient mice and peripheral CD4+ T cells. We found that Y27632 significantly up-regulated the phosphorylation level of STAT5 in both spleen and lymph nodes, down-regulated the phosphorylation level of STAT3 in the CD4+ T cells in the spleen. It also increased the proportion of CD4+CD25+Foxp3+Helios+ Tregs while decreased CD4+IL17A+ -Th17 cells. Moreover, Y27632 also reduced the proportion of dendritic cells in both spleen and lymph nodes, as well as the expression level of CD86 on their surfaces in the spleen, while the proportion of macrophages was not affected. The expression levels of ROCK1, ROCK2, CD11c and IL-17A mRNA were also found to be low in the graft tissue while the expression of Helios was upregulated. Rho-kinase inhibitor can modulate the balance of Tregs/Th17 by regulating the phosphorylation levels of both STAT3 and STAT5, thereby inhibiting the occurrence of immune rejection in allogeneic corneal transplantation.

The Yin and Yang of non-immune and immune responses in meibomian gland dysfunction

Meibomian gland dysfunction (MGD) is a leading cause of dry eye disease and one of the most common ophthalmic conditions encountered in eye clinics worldwide. These holocrine glands are situated in the eyelid, where they produce specialized lipids, or meibum, needed to lubricate the eye surface and slow tear film evaporation - functions which are critical to preserving high-resolution vision. MGD results in tear instability, rapid tear evaporation, changes in local microflora, and dry eye disease, amongst other pathological entities. While studies identifying the mechanisms of MGD have generally focused on gland obstruction, we now know that age is a major risk factor for MGD that is associated with abnormal cell differentiation and renewal. It is also now appreciated that immune-inflammatory disorders, such as certain autoimmune diseases and atopy, may trigger MGD, as demonstrated through a T cell-driven neutrophil response. Here, we independently discuss the underlying roles of gland and immune related factors in MGD, as well as the integration of these two distinct mechanisms into a unified perspective that may aid future studies. From this unique standpoint, we propose a revised model in which glandular dysfunction and immunopathogenic pathways are not primary versus secondary contributors in MGD, but are fluid, interactive, and dynamic, which we likened to the Yin and Yang of MGD.

The Effect of Oral Isotretinoin Therapy on Meibomian Gland Characteristics in Patients with Acne Vulgaris

INTRODUCTION

The aim of the study was to determine the effect of oral isotretinoin therapy on the functional and morphological condition of the anterior segment of the eye, with particular emphasis on the meibomian glands.

METHODS

Twenty-four patients (48 eyes) with a diagnosis of acne vulgaris were involved in the survey. All patients underwent a thorough ophthalmological examination at three time points: before therapy, 3 months after the start of therapy, and 1 month after the completion of isotretinoin therapy. The physical examination included the following elements: blink rate, analysis of the lid margin abnormality score (LAS), tear film break-up time (TFBUT) and Schirmer's test, meibomian gland loss (MGL), and the evaluation of the meibum quality score (MQS) and meibum expressibility score (MES). Additionally, the total score of an ocular surface disease index (OSDI) questionnaire was analysed.

RESULTS

In comparison with pretreatment values, significant increases in OSDI during and after the treatment (p = 0.003 and p = 0.004, respectively) were observed. Substantial deterioration during the treatment was observed for MGL (p < 0.0001), MQS (p < 0.001) and LAS (p < 0.0001), while an improvement in those parameters after isotretinoin cessation was observed (p = 0.006, p = 0.02 and p = 0.0003, respectively). The frequency of using artificial eye drops was positively associated with MGL during (Spearman's rank correlation coefficient (Rs) =  + 0.31; p = 0.03) and after the cessation of the therapy (Rs =  + 0.28; p = 0.04). Meibomian gland atrophy correlated significantly with MQS during (Rs =  + 0.29; p = 0.04) and after treatment (Rs =  + 0.38; p = 0.008). The decrease in TFBUT values correlated with increased LAS (Rs = - 0.31; p = 0.03) during the course of isotretinoin usage. We found no changes in Schirmer's test or blink rates.

CONCLUSION

Isotretinoin therapy leads to increased ocular complaints related to lipid tear film component dysfunction. This is due to reversible changes in meibomian gland morphology and function observed during drug usage.