Controlled release of an HDAC inhibitor for reduction of inflammation in dry eye disease.

Dry eye disease (DED), also known as keratoconjunctivitis sicca, is an ocular surface disease characterized by T-cell-mediated inflammation. Current therapeutics, such as immunosuppressive agents, act to suppress the clinical signs and inflammation. However, long-term usage of these treatments can cause severe side effects. In this study, we present an alternative therapeutic approach that utilizes a histone deacetylase inhibitor (HDACi) to regulate transcription of a variety of immunomodulatory genes. Specifically, HDACi have emerged as a potential anti-inflammatory agent, which can modulate the functions of a subset of suppressive T lymphocytes known as regulatory T cells (Tregs), enhancing FoxP3 acetylation and subsequently guarding the transcription factor from proteasomal degradation. Here, a specific HDACi known as SAHA (suberoylanilide hydroxamic acid) was formulated to controllably release in the lacrimal gland. Intralacrimal gland injection of PLGA-based SAHA microspheres prevented clinical signs of DED in mice with Concanavalin A-induced DED, reduced expression of pro-inflammatory cytokines, and increased expression of FoxP3 in the lacrimal glands. Murine T cell culture experiments also revealed that SAHA decreased effector T cell proliferation and enhanced suppressive function of Tregs in co-cultures of Tregs and effector T cells. STATEMENT OF SIGNIFICANCE: In this study, we demonstrate a therapeutic approach that utilizes a histone deactylase inhibitor (HDACi) to regulate transcription of a variety of immunomodulatory genes. HDACi have emerged as a potential anti-inflammatory agent, which can modulate the functions of a subset of suppressive T lymphocytes known as regulatory T cells (Tregs). Here, HDACi microspheres composed of a biocompatible and biodegradable polymer (poly(lactic-co-glycolic acid) (PLGA)), were able to locally release the HDACi and prevent clinical signs of DED. This work is timely given the recent shift in treatments of DED towards immunological based therapies to reduce ocular inflammation. However, notably, many of these treatments require large amounts of drug, and non-specifically suppress the immune system, leading to several systemic side effects. Instead of merely suppressing or blocking inflammation, the formulation described herein intends to balance the microenvironment promoting immunological homeostasis. This particular drug delivery system may also have broad implications in the field of inflammatory mediated ocular disorders such as uveitis, Sjögren's syndrome, allergic conjunctivitis.

Modern Therapeutic Approaches for Noninfectious Ocular Diseases Involving Inflammation.

Dry eye disease, age-related macular degeneration, and uveitis are ocular diseases that significantly affect the quality of life of millions of people each year. In these diseases, the action of chemokines, proinflammatory cytokines, and immune cells drives a local inflammatory response that results in ocular tissue damage. Multiple therapeutic strategies are developed to either address the symptoms or abate the underlying cause of these diseases. Herein, the challenges to deliver drugs to the relevant location in the eye for each of these diseases are reviewed along with current and innovative therapeutic approaches that attempt to restore homeostasis within the ocular microenvironment.

TRI Microspheres prevent key signs of dry eye disease in a murine, inflammatory model.

Dry eye disease (DED) is a highly prevalent, ocular disorder characterized by an abnormal tear film and ocular surface. Recent experimental data has suggested that the underlying pathology of DED involves inflammation of the lacrimal functional unit (LFU), comprising the cornea, conjunctiva, lacrimal gland and interconnecting innervation. This inflammation of the LFU ultimately results in tissue deterioration and the symptoms of DED. Moreover, an increase of pathogenic lymphocyte infiltration and the secretion of pro-inflammatory cytokines are involved in the propagation of DED-associated inflammation. Studies have demonstrated that the adoptive transfer of regulatory T cells (Tregs) can mediate the inflammation caused by pathogenic lymphocytes. Thus, as an approach to treating the inflammation associated with DED, we hypothesized that it was possible to enrich the body's own endogenous Tregs by locally delivering a specific combination of Treg inducing factors through degradable polymer microspheres (TRI microspheres; TGF-ß1, Rapamycin (Rapa), and IL-2). This local controlled release system is capable of shifting the balance of Treg/T effectors and, in turn, preventing key signs of dry eye disease such as aqueous tear secretion, conjunctival goblet cells, epithelial corneal integrity, and reduce the pro-inflammatory cytokine milieu in the tissue.

Treg-recruiting microspheres prevent inflammation in a murine model of dry eye disease.

Dry eye disease (DED) is a common ocular disorder affecting millions of individuals worldwide. The pathology of DED involves the infiltration of CD4+ lymphocytes, leading to tear film instability and destructive inflammation. In the healthy steady state, a population of immunosuppressive T-cells called regulatory T-cells (Treg) regulates proliferation of immune cells that would otherwise lead to a disruption of immunological homeostasis. For this reason, it has been suggested that Tregs could restore the immunological imbalance in DED. To this end, one possible approach would be to recruit the body's own, endogenous Tregs in order to enrich them at the site of inflammation and tissue destruction. Previously, we have demonstrated a reduction of inflammation and disease symptoms in models of periodontitis corresponding to recruitment of endogenous Tregs, which was accomplished by local placement of controlled release systems that sustain a gradient of the chemokine CCL22, referred to here as Treg-recruiting microspheres. Given that DED is characterized by a pro-inflammatory environment resulting in local tissue destruction, we hypothesized that the controlled release of CCL22 could also recruit Tregs to the ocular surface potentially mediating inflammation and symptoms of DED. Indeed, data suggest that Treg-recruiting microspheres are capable of overcoming the immunological imbalance of Tregs and CD4+ IFN-γ+ cells in the lacrimal gland. Administration of Treg-recruiting microspheres effectively mitigated the symptoms of DED as measured through a number of outcomes such as tear clearance, goblet cells density and corneal epithelial integrity, suggesting that recruitment of endogenous Treg can mitigate inflammation associated with DED.