N-acetylcysteine in chronic blepharitis

N-Acetylcysteine (NAC): Impacts on Human Health

N-acetylcysteine (NAC) is a medicine widely used to treat paracetamol overdose and as a mucolytic compound. It has a well-established safety profile, and its toxicity is uncommon and dependent on the route of administration and high dosages. Its remarkable antioxidant and anti-inflammatory capacity is the biochemical basis used to treat several diseases related to oxidative stress and inflammation. The primary role of NAC as an antioxidant stems from its ability to increase the intracellular concentration of glutathione (GSH), which is the most crucial biothiol responsible for cellular redox imbalance. As an anti-inflammatory compound, NAC can reduce levels of tumor necrosis factor-alpha (TNF-α) and interleukins (IL-6 and IL-1β) by suppressing the activity of nuclear factor kappa B (NF-κB). Despite NAC's relevant therapeutic potential, in several experimental studies, its effectiveness in clinical trials, addressing different pathological conditions, is still limited. Thus, the purpose of this chapter is to provide an overview of the medicinal effects and applications of NAC to human health based on current therapeutic evidence.

Cysteine/Glutathione Deficiency: A Significant and Treatable Corollary of Disease

Glutathione (GSH) deficiency may play a pivotal role in a variety of apparently unrelated clinical conditions and diseases. Orally administered N-acetylcysteine (NAC), which replenishes the cysteine required for GSH synthesis, has been tested in a large number of randomized placebo-controlled trials involving these diseases and conditions. This chapter focused on developing a base of evidence suggesting that NAC administration improves disease by increasing cysteine and/or GSH in a variety of diseases, thereby implying a significant role for GSH deficiency in the clinical basis of many diseases. To develop this base of evidence, we systematically selected studies which considered the hypothesis that the therapeutic efficacy for NAC is an indication that cysteine and/or GSH deficiency is a pathophysiological part of the diseases studied. In this manner we focus this chapter on explaining the biological mechanisms of NAC therapy in a wide variety of disorders and demonstrate its ubiquitous role in improving disease that involves disrupted GSH and/or cysteine metabolism.

Reconsidering the central role of mucins in dry eye and ocular surface diseases

Mucins are key actors in tear film quality and tear film stability. Alteration of membrane-bound mucin expression on corneal and conjunctival epithelial cells and/or gel-forming mucin secretion by goblet cells (GCs) promotes in ocular surface diseases and dry eye disease (DED). Changes in the mucin layer may lead to enhanced tear evaporation eventually contributing to tear hyperosmolarity which has been associated with ocular surface inflammation. Inflammatory mediators in turn may have a negative impact on GCs differentiation, proliferation, and mucin secretion. This sheds new light on the position of GCs in the vicious circle of DED. As contributor to ocular surface immune homeostasis, GC loss may contribute to impaired ocular surface immune tolerance observed in DED. In spite of this, there are no tools in routine clinical practice for exploring ocular surface mucin deficiency/dysregulation. Therefore, when selecting the most appropriate treatment options, there is a clear unmet need for a better understanding of the importance of mucins and options for their replacement. Here, we comprehensively revisited the current knowledge on ocular surface mucin biology, including functions, synthesis, and secretion as well as the available diagnostic tools and treatment options to improve mucin-associated homeostasis. In particular, we detailed the potential link between mucin dysfunction and inflammation as part of the uncontrolled chronic inflammation which perpetuates the vicious circle in DED.

Sulforaphane protects rabbit corneas against oxidative stress injury in keratoconus through activation of the Nrf-2/HO-1 antioxidant pathway

The aim of the present study was to examine whether activation of the nuclear factor E2-related factor 2 (Nrf-2)/heme oxygenase-1 (HO-1) antioxidant pathway in the cornea was involved in the protective effect of sulforaphane (SF) following keratoconus (KC) injury. Following epithelial debridement, collagenase type II was applied in KC groups at room temperature for 30 min. Following this, rabbits were administered with a subconjunctival (s.c.) injection of SF or placebo (maize oil) daily for a total of 2 weeks. To investigate whether HO-1 was involved in the Nrf-2-related antioxidant pathway, rabbits were injected with zinc (II) protoporphyrin IX (ZnPP IX, s.c.) treatment in combination with SF 24 h following the application of collagenase type II. The protective effects of SF were evaluated by examining the mean keratometry (Km) and central cornea thickness (CCT), measuring reactive oxygen species (ROS) production using immunofluorescent staining, and analyzing the protein expression of NADPH oxidase (Nox) family members Nox-2 and Nox-4, and Nrf-2 and HO-1 using immunohistochemistry and western blot analysis. The mRNA levels of Nox-2, Nox-4, Nrf-2 and HO-1 were quantitatively detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. No significant difference in Km or CCT was observed among groups prior to surgery (P=0.700 and P=0.982, respectively). KC induced an apparent increase of ROS generation, and caused a significant increase in Km and a significant decrease in CCT. These changes were neutralized or reversed by SF treatment. Simultaneously, SF treatment decreased the expression of Nox-2 and Nox-4, and enhanced the expression of Nrf-2 and HO-1 in the KC corneas. The RT-qPCR results indicated that SF induced downregulation of the mRNA expression of Nox-2 and Nox-4, and upregulation of the mRNA expression of Nrf-2 and HO-1 following KC injury. The HO-1 inhibitor, ZnPP IX, counteracted the protective effects of SF on KC corneas. Therefore, the present study provided evidence that activation of the Nrf-2/HO-1 signal transduction pathway may partially promote the protective effect of the antioxidant SF in the KC cornea.

NQO1 downregulation potentiates menadione-induced endothelial-mesenchymal transition during rosette formation in Fuchs endothelial corneal dystrophy

Fuchs endothelial corneal dystrophy (FECD) is a genetic and oxidative stress disorder of post-mitotic human corneal endothelial cells (HCEnCs), which normally exhibit hexagonal shape and form a compact monolayer compatible with normal corneal functioning and clear vision. FECD is associated with increased DNA damage, which in turn leads to HCEnC loss, resulting in the formation rosettes and aberrant extracellular matrix (ECM) deposition in the form of pro-fibrotic guttae. Since the mechanism of ECM deposition in FECD is currently unknown, we aimed to investigate the role of endothelial-mesenchymal transition (EMT) in FECD using a previously established cellular in vitro model that recapitulates the characteristic rosette formation, by employing menadione (MN)-induced oxidative stress. We demonstrate that MN treatment alone, or a combination of MN and TGF-β1 induces reactive oxygen species (ROS), cell death, and EMT in HCEnCs during rosette formation, resulting in upregulation of EMT- and FECD-associated markers such as Snail1, N-cadherin, ZEB1, and transforming growth factor-beta-induced (TGFβI), respectively. Additionally, FECD ex vivo specimens displayed a loss of organized junctional staining of plasma membrane-bound N-cadherin, with corresponding increase in fibronectin and Snail1 compared to ex vivo controls. Addition of N-acetylcysteine (NAC) downregulated all EMT markers and abolished rosette formation. Loss of NQO1, a metabolizing enzyme of MN, led to greater increase in intracellular ROS levels as well as a significant upregulation of Snail1, fibronectin, and N-cadherin compared to normal cells, indicating that NQO1 regulates Snail1-mediated EMT. This study provides first line evidence that MN-induced oxidative stress leads to EMT in corneal endothelial cells, and the effect of which is further potentiated when redox cycling activity of MN is enhanced by the absence of NQO1. Given that NAC inhibits Snail-mediated EMT, this may be a potential therapeutic intervention for FECD.

N-acetylcysteine for non-paracetamol drug-induced liver injury: a systematic review

AIMS

N-acetylcysteine (NAC) may be useful in the management of non-paracetamol drug-induced liver injury (DILI). Our objective was to review systematically evidence for the use of NAC as a therapeutic option for non-paracetamol DILI.

METHODS

We searched for randomized controlled trials (RCTs) and prospective cohort studies. We searched several bibliographic databases, grey literature sources, conference proceedings and ongoing trials. Our pre-specified primary outcomes were all cause and DILI related mortality, time to normalization of liver biochemistry and adverse events. Secondary outcomes were proportion receiving liver transplant, time to transplantation, transplant-free survival and hospitalization duration.

RESULTS

We identified one RCT of NAC vs. placebo in patients with non-paracetamol acute liver failure. There was no difference in the primary outcomes of overall survival at 3 weeks between NAC [70%, 95% confidence interval (CI) = 60%, 81%, n = 81] and placebo (66%, 95% CI = 56%, 77%, n = 92). NAC significantly improved the secondary outcomes of transplant-free survival compared with placebo: 40% NAC (95% CI = 28%, 51%) vs. 27% placebo (95% CI = 18%, 37%). A subgroup analysis according to aetiology found improved transplant-free survival in patients with non-paracetamol DILI, NAC (58%, n = 19) vs. placebo (27%, n = 26), odds ratio (OR) 0.27 (95% CI = 0.076, 0.942). Overall survival was similar, NAC (79%) vs. placebo (65%);, OR 0.50 (95% CI = 0.13, 1.98).

CONCLUSION

Current available evidence is limited and does not allow for any firm conclusions to be made regarding the role of NAC in non-paracetamol DILI. We therefore highlight the need for further research in this area.

N-acetylcysteine for non-paracetamol drug-induced liver injury: a systematic review protocol

BACKGROUND

Drug-induced liver injury (DILI) refers to acute or chronic liver injury that may occur as a consequence of using drugs and herbal or dietary supplements. Specific therapies for DILI are limited. There is considerable evidence for efficacy and safety of N-acetylcysteine (NAC) in management of paracetamol-induced liver injury. More recently, research has explored the use of NAC in non-paracetamol drug-induced liver injury. It is important to summarise the evidence of NAC for non-paracetamol DILI to determine if NAC may be considered a therapeutic option in this condition.

METHODS/DESIGN

We will conduct a systematic review of the benefit and harm of NAC in non-paracetamol drug-induced liver injury. Primary and secondary outcomes of interest are pre-specified. Primary outcomes include all-cause mortality, mortality due to DILI, time to normalisation of liver biochemistry (e.g. return of alanine transaminase to <100 U/l and/or international normalized ratio (INR) <1.5) and adverse events. Secondary outcomes include transplantation rate, time to transplantation, transplant-free survival and duration of hospitalisation. We will include randomized controlled trials (RCTs) and prospective cohort studies. RCTs will contribute to the evaluation of safety and efficacy of NAC, whereas, the cohort studies will contribute exclusively to the evaluation of safety. We will search several bibliographic databases (including PubMed, Scopus, CINAHL, CENTRAL), grey literature sources, conference proceedings and ongoing trials. Following data extraction and assessment of the risk of bias, we will conduct a meta-analysis if feasible, as well as subgroup analyses. We will assess and explore clinical and statistical heterogeneity.

DISCUSSION

The aim of this review is to provide evidence on the effectiveness and safety of NAC in non-paracetamol DILI. We anticipate that the results could aid health care practitioners, researchers and policymakers in the decision-making regarding the use of NAC in patients with non-paracetamol DILI.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42014008771.

Evaluation of dry eye and meibomian gland dysfunction after cataract surgery

PURPOSE

To evaluate dry eye and meibomian gland dysfunction after cataract surgery.

DESIGN

Prospective observational case series.

METHODS

We studied 58 eyes of 48 patients who underwent phacoemulsification and evaluated them preoperatively and at 1 month and 3 months postoperatively. Ocular symptom scores, lid margin abnormalities, superficial punctate keratopathies (SPKs), tear film break-up time (TBUT), Schirmer test, lower tear meniscus height, depth, and area using Fourier domain optical coherence tomography, meibum expressibility and images of the meibomian glands using meibography were measured.

RESULTS

The ocular symptom scores were worse at 1 month and 3 months postoperatively (P < 0.001 and P < 0.001, respectively). Lid margin abnormalities were significantly increased (P < 0.001 and P < 0.001, respectively) and TBUT decreased postoperatively (P < 0.001 and P < 0.001, respectively). Meibum expressibility decreased at 3 months postoperatively (P = 0.016); however, meibography score, SPK, lower tear meniscus height, depth and area and the Schirmer test did not change significantly postoperatively (all P values >0.05).

CONCLUSION

Meibomian gland function may be altered without accompanying structural changes after cataract surgery.

Comparação entre dois protocolos de tratamento de ceratoconjuntivite seca experimentalmente induzida em coelhos

O objetivo deste estudo foi avaliar e comparar a eficácia de dois protocolos de tratamento de ceratoconjuntivite seca (CCS) experimentalmente induzida em coelhos: uma formulação oftálmica tópica composta por álcool polivinílico 1,4%, adicionado com acetilcisteína 10% e pilocarpina 1% (AAP), e outro protocolo com o uso do óleo de semente de linhaça (OL) tópico em forma de colírio, durante 12 semanas. Foram utilizados 15 coelhos machos, adultos, da raça Nova Zelândia, alocados aleatoriamente em três grupos: grupo C (controle), grupo AAP (formulação oftálmica) e grupo L (OL tópica). Os animais foram avaliados semanalmente pelo teste lacrimal de Schirmer, teste de fluoresceína e teste de Rosa Bengala; uma vez por mês, pelo exame de citologia esfoliativa ocular; ao final do experimento, pela análise histopatológica da córnea e conjuntiva. Os resultados demonstraram que houve um aumento maior na produção lacrimal quando utilizada a formulação oftálmica, e uma resolução mais rápida das úlceras de córnea, bem como diminuição no número de células desvitalizadas quando utilizado o óleo de semente de linhaça, além de aumento no número de células caliciformes em ambos os grupos de tratamento. A associação desses dois protocolos pode ser no futuro uma alternativa no tratamento da CCS.

Interventions for chronic blepharitis

BACKGROUND

Blepharitis, an inflammatory condition associated with itchiness, redness, flaking, and crusting of the eyelids, is a common eye condition that affects both children and adults. It is common in all ethnic groups and across all ages. Although infrequent, blepharitis can lead to permanent alterations to the eyelid margin or vision loss from superficial keratopathy (abnormality of the cornea), corneal neovascularization, and ulceration. Most importantly, blepharitis frequently causes significant ocular symptoms such as burning sensation, irritation, tearing, and red eyes as well as visual problems such as photophobia and blurred vision. The exact etiopathogenesis is unknown, but suspected to be multifactorial, including chronic low-grade infections of the ocular surface with bacteria, infestations with certain parasites such as demodex, and inflammatory skin conditions such as atopy and seborrhea. Blepharitis can be categorized in several different ways. First, categorization is based on the length of disease process: acute or chronic blepharitis. Second, categorization is based on the anatomical location of disease: anterior, or front of the eye (e.g. staphylococcal and seborrheic blepharitis), and posterior, or back of the eye (e.g. meibomian gland dysfunction (MGD)). This review focuses on chronic blepharitis and stratifies anterior and posterior blepharitis.

OBJECTIVES

To examine the effectiveness of interventions in the treatment of chronic blepharitis.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 1), MEDLINE (January 1950 to February 2012), EMBASE (January 1980 to February 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We searched the reference lists of included studies for any additional studies not identified by the electronic searches. There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 9 February 2012.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and quasi-randomized controlled trials (CCTs) in which participants were adults aged 16 years or older and clinically diagnosed with chronic blepharitis. We also included trials where participants with chronic blepharitis were a subset of the participants included in the study and data were reported separately for these participants. Interventions within the scope of this review included medical treatment and lid hygiene measures.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed search results, reviewed full-text copies for eligibility, examined risk of bias, and extracted data. Data were meta-analyzed for studies comparing similar interventions and reporting comparable outcomes with the same timing. Otherwise, results for included studies were summarized in the text.

MAIN RESULTS

There were 34 studies (2169 participants with blepharitis) included in this review: 20 studies (14 RCTs and 6 CCTs) included 1661 participants with anterior or mixed blepharitis and 14 studies (12 RCTs and 2 CCTs) included 508 participants with posterior blepharitis (MGD). Due to the heterogeneity of study characteristics among the included studies, with respect to follow-up periods and types of interventions, comparisons, and condition of participants, our ability to perform meta-analyses was limited. Topical antibiotics were shown to provide some symptomatic relief and were effective in eradicating bacteria from the eyelid margin for anterior blepharitis. Lid hygiene may provide symptomatic relief for anterior and posterior blepharitis. The effectiveness of other treatments for blepharitis, such as topical steroids and oral antibiotics, were inconclusive.

AUTHORS' CONCLUSIONS

Despite identifying 34 trials related to treatments for blepharitis, there is no strong evidence for any of the treatments in terms of curing chronic blepharitis. Commercial products are marketed to consumers and prescribed to patients without substantial evidence of effectiveness. Further research is needed to evaluate the effectiveness of such treatments. Any RCT designed for this purpose should separate participants by type of condition (e.g. staphylococcal blepharitis or MGD) in order to minimize imbalances between groups (type I errors) and to achieve statistical power for analyses (prevent type II errors). Medical interventions and commercial products should be compared with conventional lid hygiene measures, such as warm compresses and eyelid margin washing, to determine effectiveness, as well as head-to-head to show comparative effectiveness between treatments. Outcomes of interest should be patient-centered and measured using validated questionnaires or scales. It is important that participants be followed long-term, at least one year, to assess chronic outcomes properly.

Efficacy of topical N-acetylcysteine in the treatment of meibomian gland dysfunction

PURPOSE

To evaluate the efficacy of topical N-acetyl-cysteine (NAC) therapy in patients with meibomian gland dysfunction (MGD).

METHODS

Twenty patients with MGD were prospectively randomized and assigned into 2 groups. The patients were instructed to use either NAC 5% or preservative-free artificial tear topically 4 times a day for a month. All patients were instructed to apply lid hygiene once daily. Preservative-free artificial tears treated group served as control. Paired sample Student's t-tests were used to detect differences between the baseline and 1 month after treatment initiation in mean ocular symptoms, fluorescein break-up time (FBUT) values, and Schirmer scores in each group. Difference in mean ocular symptoms, Schirmer's test scores, and FBUT values between the baseline and 1 month after treatment initiation were compared between the groups using Mann-Whitney U test.

RESULTS

One month of topical NAC therapy provided statistically significant improvements in FBUT and Schirmer scores as compared with the initial study visit. The average Schirmer increase rate was significantly better in the NAC group than in the control group. Significant improvements for the symptoms of ocular burning, foreign body sensation, and intermittent filmy or blurred vision were noted in both groups; and only NAC-treated group showed improvement for the symptom of itching, at 1 month as compared with 1 day. NAC provided significantly better improvement in itching symptom when compared with controls.

CONCLUSIONS

Topical administration of NAC is thought to be effective and well tolerated in patients with MGD.

N-acetylcysteine -- passe-partout or much ado about nothing?

In experimental studies, the old mucolytic agent N-acetylcysteine (NAC) has had beneficial effects in disorders supposedly linked to oxidative stress. Numerous, mainly small clinical trials with variable doses have yielded inconsistent results in a wide variety of diseases. NAC added to the conventional therapy of human immunodeficiency virus infection might be of benefit; in respect of chronic obstructive pulmonary disease, systematic reviews and meta-analyses suggested that prolonged treatment with NAC is efficacious, but a recent multicentre study has questioned this. In a large intervention trial on cancer recurrence, NAC was ineffective. NAC infusions have been widely used in acute hepatic failure but convincing evidence of its benefits is lacking. A preliminary study reported that NAC is effective in preventing radiocontrast-induced nephropathy but thereafter highly mixed results have been published, and even meta-analyses disagree on its efficacy. In intensive care NAC has mostly been a disappointment but recently it has 'given promises' in surgery with cardiopulmonary bypass. NAC therapy is routine only in paracetamol intoxication.