Inhibition of cellular transfer of experimental autoimmune uveoretinitis by Rapamycin

Rapamycin ameliorates experimental autoimmune uveoretinitis by inhibiting Th1/Th2/Th17 cells and upregulating CD4+CD25+ Foxp3 regulatory T cells

AIM

To determine the effects of rapamycin on experimental autoimmune uveoretinitis (EAU) and investigate of role of rapamycin on T cell subsets in the disease.

METHODS

EAU was induced in rats using peptides 1169 to 1191 of the interphotoreceptor binding protein (IRBP). Rapamycin (0.2 mg/kg/d) was administrated by intraperitoneal injection for a consecutive 7d after immunization. Th1/Th2/Th17 cytokines, TGF-β1, and IL-6 produced by lymphocyteswere measured by ELISA, while Th17 cells and CD4+CD25+ regulatory T cells (Tregs) from rat spleen were detected by flow cytometry.

RESULTS

Intraperitoneal treatment immediately after immunization dramatically ameliorated the clinical course of EAU. Clinical responses were associated with reduced retinal inflammatory cell infiltration and tissue destruction. Rapamycin induced suppression of Th1/Th2/Th17 cytokines, including IFN-γ, IL-2, IL-17, IL-4, and IL-10 release from T lymphocytes of EAU rats, in vitro. Rapamycin also significantly increased TGF-β1 production but had no effect on IL-6 productionof T lymphocytes from EAU rats in vitro. Furthermore, rapamycin decreased the ratio of Th17 cells/CD4+T cells and upregulated Tregs in EAU, as detected by flow cytometry.

CONCLUSION

Rapamycin effectively interferes with T cell mediated autoimmune uveitis by inhibiting antigen-specific T cell functions and enhancing Tregs in EAU. Rapamycin is a promising new alternative as an adjunct corticosteroid-sparing agent for treating uveitis.

A comprehensive review and update on the non-biologic treatment of adult noninfectious uveitis: part I

INTRODUCTION

Treatment of adult, noninfectious uveitis remains a challenge for ophthalmologists around the world. The disease accounts for almost 10% of preventable blindness in the US and can be idiopathic or associated with infectious and systemic disorders. Strong evidence is still emerging to indicate that pharmacologic strategies presently used in rheumatologic or autoimmune disease may be translated to the treatment of intraocular inflammation. Corticosteroid monotherapy is widely regarded as wholly inappropriate, due to the unfavorable risk/benefit profile and poor long-term outcomes. Treatment plans have shifted away from low-dose, chronic corticosteroid therapy for maintenance, towards medium- to high-dose therapy for acute inflammation, followed immediately by initiation of immunomodulatory therapy. These therapies follow the 'stepladder approach', whereby least to more aggressive therapies are trialed to induce remission of inflammation, eventually without corticosteroids of any form (topical, local and systemic).

AREAS COVERED

This two-part review gives a comprehensive overview of the existing medical treatment options for patients with adult, noninfectious uveitis, as well as important advances for the treatment of ocular inflammation. Part I covers classic immunomodulation and latest information on corticosteroid therapy.

EXPERT OPINION

The hazard of chronic corticosteroid use for the treatment of adult, noninfectious uveitis is well-documented. Corticosteroid-sparing therapies, which offer a very favorable risk-benefit profile when administered properly, should be substituted.

Synergism between corticosteroids and Rapamycin for the treatment of intraocular inflammation

The authors studied the combination effect of corticosteroids with the new immunosuppressant Rapamycin for the treatment of intraocular inflammation. A median-effect analysis, of the combined effect of Rapamycin and dexamethasone, was performed on the inhibition of lymphocyte proliferation in culture. The mathematical formulas allowed for the calculation of combination indices and dose-reduction factors. On the basis of these in-vitro results, treatment with reduced doses of drugs in combination was evaluated in the rat model of experimental autoimmune uveoretinitis. The results showed that Rapamycin and dexamethasone were synergistic over a wide concentration range. The calculated dose reduction factors indicated that an equivalent inhibition of lymphocyte proliferation was achieved with a combination of Rapamycin and dexamethasone reduced by 5-7 and 3-6 fold respectively, compared to the concentration required when each drug was used alone. In animals, there was a significant reduction of the incidence and severity of ocular inflammation with low doses of the drugs in combination. The authors conclude that the observed synergistic effect between Rapamycin and dexamethasone suggests that the use of this drug combination might be advantageous in the treatment of patients with severe uveitis.

The pathogenesis and clinical presentation of macular edema in inflammatory diseases

Cystoid macular edema (CME) is a classical complication of ocular inflammation. This syndrome was already described by Irvine in 1953 but the pathogenesis of this condition remains unclear. Cystoid macular edema can result either from a rupture of the inner or from the outer blood ocular barrier. Clinical CME that is responsible for a low visual acuity must be differentiated from angiographic CME that can be present even without any decrease in visual acuity. Fluid progressively accumulates into the outer plexiform layer of the retina and pools into cystic spaces. Fluid accumulation can now be better seen with optical coherence tomography (OCT). In chronic CME fluid accumulation is associated with thinning of the retina and fibrosis. At this stage irreversible lesions are present and CME does not respond to medical therapies. Inflammatory CME must be differentiated from CME resulting from irreversible vascular damage such as in diabetic CME or due to vein occlusions. Experimental research on cystoid macular edema has been hampered by the lack of animal model: most of laboratory animals have no macula, monkeys appear to be highly resistant to macular edema. Five major causes have been suspected to be at the origin of CME: (1) photic retinopathy, (2) trauma of ocular tissue, (3) secondary irritation of the ciliary body, (4) vitreous traction and (5) pharmaceutically induced CME. Clinical experience has shown that pseudophakic CME usually responds well to local therapy of steroids and non-steroidal antiinflammatory drugs (NSAIDs) and/or in association with systemic acetazolamide. Acetazolamide is increasing fluid resorption through the retinal pigment epithelium. Postoperative CME rarely needs additional posterior subtenon's injections to resolve. But in CME occurring secondary to uveitis additional posterior sub-Tenon's steroid injections or systemic steroids may be necessary to decrease the constant release of inflammatory mediators.

The pathogenesis and clinical presentation of macular edema in inflammatory diseases

Cystoid macular edema (CME) is a classical complication of ocular inflammation. This syndrome was already described by Irvine in 1953 but the pathogenesis of this condition remains unclear. Cystoid macular edema can result either from a rupture of the inner or from the outer blood ocular barrier. Clinical CME that is responsible for a low visual acuity must be differentiated from angiographic CME that can be present even without any decrease in visual acuity. Fluid progressively accumulates into the outer plexiform layer of the retina and pools into cystic spaces. Fluid accumulation can now be better seen with optical coherence tomography (OCT). In chronic CME fluid accumulation is associated with thinning of the retina and fibrosis. At this stage irreversible lesions are present and CME does not respond to medical therapies. Inflammatory CME must be differentiated from CME resulting from irreversible vascular damage such as in diabetic CME or due to vein occlusions. Experimental research on cystoid macular edema has been hampered by the lack of animal model: most of laboratory animals have no macula, monkeys appear to be highly resistant to macular edema. Five major causes have been suspected to be at the origin of CME: (1) photic retinopathy, (2) trauma of ocular tissue, (3) secondary irritation of the ciliary body, (4) vitreous traction and (5) pharmaceutically induced CME. Clinical experience has shown that pseudophakic CME usually responds well to local therapy of steroids and non-steroidal antiinflammatory drugs (NSAIDs) and/or in association with systemic acetazolamide. Acetazolamide is increasing fluid resorption through the retinal pigment epithelium. Postoperative CME rarely needs additional posterior subtenon's injections to resolve. But in CME occurring secondary to uveitis additional posterior sub-Tenon's steroid injections or systemic steroids may be necessary to decrease the constant release of inflammatory mediators.

Side effects of rapamycin in the rat

The side effects of Rapamycin was evaluated by histopathological examination of the heart, kidneys, and eyes of treated Lewis rats. Rapamycin was administered during 14 days by continuous intravenous infusions at doses of 0.5, 1.0, and 1.5 mg/kg/day. Focal myocardial infarction was observed in three of five rats with Rapamycin given at 1.5 mg/kg/day and two of 22 rats with 1.0 mg/kg/day. There were no sign of myocardial toxicity at a Rapamycin dose of 0.5 mg/kg/day. The retina of one eye of a rat treated at a dose of 1.5 mg/kg/day had a small area of focal ischemic necrosis. The kidneys were normal at all doses.