In vitro modulation of preservative toxicity: high molecular weight hyaluronan decreases apoptosis and oxidative stress induced by benzalkonium chloride. Eur J Pharm Sci. 2008;34:263-273. [PMID: 18534829 DOI: 10.1016/j.ejps.2008.04.006]

Glycosaminoglycans and neuroprotection

Glycosaminoglycans (GAGs) are basic building blocks of the ground substance of the extracellular matrix and present at the cellular level as an important component of the glycocalyx covering the cell membrane. In addition to the general role of GAGs in maintaining the integrity of the cell and extracellular matrix by retaining water, certain GAGs exhibit anticoagulant and neuroprotective properties and serve as cell-surface receptors for various molecules. Although heparin, a highly sulfated GAG, has been used as a drug for more than 70 years due to its anticoagulant attributes, the neuroprotective properties of GAGs came into focus only in recent years. The discovery of some of the roles GAGs play in the pathomechanism of numerous neurodegenerative disorders as well as shedding light on the neuroprotective properties of these compounds in animal studies raised the possibility that GAGs may provide an entirely new avenue in the treatment of neurodegenerative diseases. Indeed, some GAGs were successfully used to improve the cognitive function of patients with various neurodegenerative conditions (Ban et al. (1991, 1992); Conti et al. (1989a, b); Passeri and Cucinotta, (1989); Santini (1989). Although the mechanism by which the GAGs exhibit neuroprotective properties is not entirely clear, there is a general consensus that the major factors of the neuroprotective attributes of GAGs include the impact of GAGs on amyloidogenesis and the regulatory action of GAGs in the apoptotic pathway.

Accidental benzalkonium chloride (zephiran) injection

We report a case of an accidental injection of benzalkonium chloride (zephiran) instead of a local anesthetic agent during a tooth extraction. The sudden development of chin and neck swelling led to dyspnea and the patient lost consciousness. She was sent to an emergency clinic by her dentist immediately. After medical treatment for 20 days, the necrotic tissue was debrided and a gingival sulcoplasty was performed. Healing was uneventful.

The effect of hyaluronan on airway mucus transport and airway epithelial barrier integrity: potential application to the cytoprotection of airway tissue

The lubricating abilities and the protective functions of hyaluronan, a structural component of interstitial and connective tissues, were assessed in in vitro models of airway mucus transport and epithelial barrier. We found that hyaluronan enhanced the transport of airway mucus by cilia and by cough: the lower the hyaluronan molecular weight, the higher the increase. By immunofluorescence and western blot, we observed a significant dose-dependent (0.1, 1, 5 and 10 mg/ml) increase by low molecular weight hyaluronan (40 kDa) in the expression of tight junction proteins such as ZO-1, as well as an increase in the trans-epithelial resistance. Incubation of airway epithelial cells with hyaluronan 40 kDa also significantly increased the gap junction functionality. Finally, we demonstrated that hyaluronan 40 kDa protects the airway epithelium against injury induced by bacterial products during infection. These results demonstrate that the expression and functionality of intercellular adhesion molecules are increased by hyaluronan which can also act as a lubricant at the airway epithelium surface and suggest that hyaluronan may play a therapeutic role in a variety of respiratory diseases.

[Hyaluronan in inflammation, auto-immunity and cardio-vascular diseases]

Hyaluronan (H) is an ubiquitous high-molecular size glycosaminoglycan involved in many physiological functions. Evidences are numerous implying H in various pathological pathways, such as inflammation, cancer cardio-vascular diseases. CD44 is the principal membrane cell receptor of H. In inflammation, H has size-specific different biological activities. The high molecular weight H are anti-angiogenic, anti-inflammatory and immunosuppressive. Smaller H oligomers are angiogenic, inflammatory and immuno-stimulatory. H is strongly involved in the recruitment of leucocytes at the site of inflammation (role of CD44). Data giving evidence for a role of H in allergic pathways and auto-immunity are scarce. H is implicated in pathogenetic process leading to atherosclerosis.

Zinc polycarboxylate dental cement for the controlled release of an active organic substance: proof of concept

The potential of employing zinc polycarboxylate dental cement as a controlled release material has been studied. Benzalkonium chloride was used as the active ingredient, and incorporated at concentrations of 1, 2 and 3% by mass within the cement. At these levels, there was no observable effect on the speed of setting. Release was followed using an ion-selective electrode to determine changes in chloride ion concentration with time. This technique showed that the additive was released when the cured cement was placed in water, with release occurring by a diffusion mechanism for the first 3 h, but continuing beyond that for up to 1 week. Diffusion coefficients were in the range 5.62 x 10(-6) cm(2) s(-1) (for 1% concentration) to 10.90 x 10(-6) cm(2) s(-1) (for 3% concentration). Up to 3% of the total loading of benzalkonium chloride was released from the zinc polycarboxylate after a week, which is similar to that found in previous studies with glass-ionomer cement. It is concluded that zinc polycarboxylate cement is capable of acting as a useful material for the controlled release of active organic compounds.

Preservatives in eyedrops: the good, the bad and the ugly

There is a large body of evidence from experimental and clinical studies showing that the long-term use of topical drugs may induce ocular surface changes, causing ocular discomfort, tear film instability, conjunctival inflammation, subconjunctival fibrosis, epithelial apoptosis, corneal surface impairment, and the potential risk of failure for further glaucoma surgery. Subclinical inflammation has also been described in patients receiving antiglaucoma treatments for long periods of time. However, the mechanisms involved, i.e., allergic, toxic, or inflammatory, as well as the respective roles of the active compound and the preservative in inducing the toxic and/or proinflammatory effects of ophthalmic solutions, is still being debated. The most frequently used preservative, benzalkonium chloride (BAK), has consistently demonstrated its toxic effects in laboratory, experimental, and clinical studies. As a quaternary ammonium, this compound has been shown to cause tear film instability, loss of goblet cells, conjunctival squamous metaplasia and apoptosis, disruption of the corneal epithelium barrier, and damage to deeper ocular tissues. The mechanisms causing these effects have not been fully elucidated, although the involvement of immunoinflammatory reactions with the release of proinflammatory cytokines, apoptosis, oxidative stress, as well as direct interactions with the lipid components of the tear film and cell membranes have been well established. Preservative-induced adverse effects are therefore far from being restricted to only allergic reactions, and side effects are often very difficult to identify because they mostly occur in a delayed or poorly specific manner. Care should therefore be taken to avoid the long-term use of preservatives, otherwise a less toxic alternative to BAK should be developed, as this weakly allergenic but highly toxic compound exerts dose- and time-dependent effects. On the basis of all these experimental and clinical reports, it would be advisable to use benzalkonium-free solutions whenever possible, especially in patients with the greatest exposure to high doses or prolonged treatments, in those suffering from preexisting or concomitant ocular surface diseases, and those experiencing side effects related to the ocular surface. Indeed, mild symptoms should not be underestimated, neglected, or denied, because they may very well be the apparent manifestations of more severe, potentially threatening subclinical reactions that may later cause major concerns.

Corneal protection with high-molecular-weight hyaluronan against in vitro and in vivo sodium lauryl sulfate-induced toxic effects

PURPOSE

The aim of this study was to investigate high-molecular-weight hyaluronan (HA-HMW) corneal protection against sodium lauryl sulfate (SLS)-induced toxic effects with in vitro and in vivo experimental approaches.

METHODS

In vitro experiments consisted of a human corneal epithelial cell line incubated with HA-HMW, rinsed, and incubated with SLS. Cell viability, oxidative stress, chromatin condensation, caspase-3, -8, -9, and P2X7 cell death receptor activation, interleukin-6, and interleukin-8 production were investigated. In vivo experiments consisted of 36 New Zealand white rabbits treated for 3 days, 3 times per day, with HA-HMW or phosphate-buffered salt solution. At day 4, eyes were treated with SLS. Clinical observation and in vivo confocal microscopy using the Rostock Cornea Module of the Heidelberg Retina Tomograph-II were performed to evaluate and to compare SLS-induced toxicity between eyes treated with HA-HMW and eyes treated with phosphate-buffered salt solution.

RESULTS

In vitro data indicate that exposure of human corneal epithelial cells to HA-HMW significantly decreased SLS-induced oxidative stress, apoptosis, and inflammation cytokine production. In vivo data indicate that SLS cornea injuries, characterized by damaged corneal epithelium, damaged anterior stroma, and inflammatory infiltrations, were attenuated with HA-HMW treatment.

CONCLUSIONS

A good correlation was seen between in vitro and in vivo findings showing that HA-HMW decreases SLS-induced toxic effects and protects cornea.

In vitro cytotoxic effects of benzalkonium chloride in corticosteroid injection suspension

BACKGROUND

Some deleterious effects on cartilage and even severe arthropathy have been reported after intra-articular corticosteroid injections. The objective of the present in vitro study was to determine if an injectable corticosteroid suspension is toxic to articular chondrocytes and synovial cells.

METHODS

Human and bovine articular chondrocytes, bovine synovial cells, mouse C3H10T1/2 cells, and human osteosarcoma MG-63 cells were treated for thirty minutes in monolayer or suspension culture with an injectable corticosteroid suspension or its chemical components, including betamethasone sodium phosphate, betamethasone acetate, and benzalkonium chloride (as preservative). Cell viability was determined by means of microscopy or flow cytometry analysis.

RESULTS

In monolayer culture, the betamethasone corticosteroids per se did not cause cell death, whereas benzalkonium chloride caused death of articular chondrocytes. In suspension culture, betamethasone sodium phosphate at dosages of as high as 6 mg/mL did not cause significant death of human or bovine articular chondrocytes (p > 0.05). In contrast, benzalkonium chloride caused a death rate of 10.6% in human articular chondrocytes at a dosage of 10 microg/mL (p < 0.01), 21.0% at a dosage of 13.3 microg/mL (p < 0.01), and 99.3% and 99.4% at dosages of 20 and 200 microg/mL, respectively (p < 0.001 for both). Similarly, benzalkonium chloride caused death of bovine articular chondrocytes, bovine synovial cells, C3H10T1/2 cells, and MG-63 cells in a dose-dependent manner. When treated with a combination of betamethasone sodium phosphate and 200 microg/mL benzalkonium chloride, >99% of human or bovine articular chondrocytes were dead (p < 0.001).

CONCLUSIONS

The injectable corticosteroid suspension caused death in in vitro culture of human and bovine articular chondrocytes as well as bovine synovial cells because of its preservative benzalkonium chloride. The betamethasone corticosteroids per se did not cause significant chondrocyte death under the conditions tested.