Intravenous dexamethasone vs methylprednisolone pulse therapy in the treatment of acute endothelial graft rejection

Management and prevention of corneal graft rejection

The management of an episode of corneal graft rejection (CGR) is primarily by corticosteroids. Immunomodulators are useful for long-term immunosuppression and in dealing with cases of high-risk (HR) corneal grafts. The classical signs of CGR following penetrating keratoplasty (PKP) include rejection line, anterior chamber (AC) reaction, and graft edema. However, these signs may be absent or subtle in cases of endothelial keratoplasty (EK). Prevention of an episode of graft rejection is of utmost importance as it can reduce the need for donor cornea significantly. In our previous article (IJO_2866_22), we had discussed about the immunopathogenesis of CGR. In this review article, we aim to discuss the various clinical aspects and management of CGR.

Antibody-mediated rejection in xenotransplantation: Can it be prevented or reversed?

Antibody-mediated rejection (AMR) is the commonest cause of failure of a pig graft after transplantation into an immunosuppressed nonhuman primate (NHP). The incidence of AMR compared to acute cellular rejection is much higher in xenotransplantation (46% vs. 7%) than in allotransplantation (3% vs. 63%) in NHPs. Although AMR in an allograft can often be reversed, to our knowledge there is no report of its successful reversal in a pig xenograft. As there is less experience in preventing or reversing AMR in models of xenotransplantation, the results of studies in patients with allografts provide more information. These include (i) depletion or neutralization of serum anti-donor antibodies, (ii) inhibition of complement activation, (iii) therapies targeting B or plasma cells, and (iv) anti-inflammatory therapy. Depletion or neutralization of anti-pig antibody, for example, by plasmapheresis, is effective in depleting antibodies, but they recover within days. IgG-degrading enzymes do not deplete IgM. Despite the expression of human complement-regulatory proteins on the pig graft, inhibition of systemic complement activation may be necessary, particularly if AMR is to be reversed. Potential therapies include (i) inhibition of complement activation (e.g., by IVIg, C1 INH, or an anti-C5 antibody), but some complement inhibitors are not effective in NHPs, for example, eculizumab. Possible B cell-targeted therapies include (i) B cell depletion, (ii) plasma cell depletion, (iii) modulation of B cell activation, and (iv) enhancing the generation of regulatory B and/or T cells. Among anti-inflammatory agents, anti-IL6R mAb and TNF blockers are increasingly being tested in xenotransplantation models, but with no definitive evidence that they reverse AMR. Increasing attention should be directed toward testing combinations of the above therapies. We suggest that treatment with a systemic complement inhibitor is likely to be most effective, possibly combined with anti-inflammatory agents (if these are not already being administered). Ultimately, it may require further genetic engineering of the organ-source pig to resolve the problem entirely, for example, knockout or knockdown of SLA, and/or expression of PD-L1, HLA E, and/or HLA-G.

Corticosteroids in the Management of Infectious Keratitis: A Concise Review

Microbial keratitis is devastating corneal morbidity with a variable spectrum of clinical manifestations depending on the infective etiology. Irrespective of the varied presentation delayed treatment can lead to severe visual impairment resulting from corneal ulceration, possible perforation, and subsequent scarring. Corticosteroids with a potent anti-inflammatory activity reduce host inflammation, thus minimizing resultant scarring while improving ocular symptoms. These potential effects of corticosteroids have been applied widely to treat various corneal diseases ranging from vernal keratoconjunctivitis to dry eye disease. However, antimicrobial therapy remains the mainstay of treatment in microbial keratitis, whereas the use of adjunctive topical corticosteroid therapy remains a matter of debate. Understandably, the use of topical corticosteroids is a double-edged sword with pros and cons in the treatment of microbial keratitis. Herein we review the rationale for and against the use and safety of topical corticosteroids in the treatment of infective keratitis. Important considerations, including type, dose, efficacy, the timing of initiation of corticosteroids, use of concomitant antimicrobial agents, and duration of corticosteroid therapy while prescribing corticosteroids for microbial keratitis, have been discussed. This review intends to provide new insights into the therapeutic utility of steroids as adjunctive treatment of corneal ulcer.

Combined intravenous pulse and topical corticosteroid therapy for severe alopecia areata in children: Comparison of two regimens

There is no universally accepted treatment for severe pediatric alopecia areata (AA). This prospective study comprised 73 patients (aged 1-18 years) with severe AA (>30% of scalp surface area): 37 received 1-day intravenous dexamethasone pulses (1-DP) and 36 received 3-day pulses (3-DP), monthly, for 6-12 months. Also, all patients applied topical clobetasol propionate under plastic wrap occlusion. Patients achieving >50% regrowth were considered good responders (GR). All patients reached short term, while 65/73 were available for the long-term follow-up (mean 33.3 ± 15.3 vs. 27.7 ± 14.3 months, 1-DP and 3-DP, respectively). Relapses during therapy were more frequent in 1-DP group. 3-DP patients were more frequently GR in comparison with 1-DP. 3-DP patients with disease duration <6 months had better outcomes. Patients without Hashimoto thyroiditis (HT) had 9.8-fold higher chance of being GR in comparison with HT patients. The best results were achieved in AA plurifocalis (AAP). No patient had severe short-term side-effects. At the long-term follow-up, 67% of 3-DP patients had stable results. Only 14.2% AAP patients experienced relapses. Patients had no long-term side-effects. 3-DP were more efficacious than 1-DP. Short disease duration and no HT were good prognostic factors. 3-DP protocol is well-tolerated, with beneficial effects and long-lasting results in severe pediatric AA.

Corticosteroids in the management of acute multiple sclerosis exacerbations

Multiple sclerosis (MS) is an autoimmune, inflammatory demyelinating disease of the central nervous system characterized in the majority of the patients by a relapsing-remitting disease course. For decades high-dosage corticosteroids (CS) are considered the cornerstone in the management of acute MS relapses. However, many unanswered questions remain when it comes to the exact modalities of CS administration. In this review on behalf of the Belgian Study Group for MS we define the efficacy of CS in reducing MS-related morbidity and examine whether the effect is different according to type of CS, route of administration, cumulative dosage, timing of initiation and disease course. We also review the use of CS in combination with other MS treatments and during pregnancy and lactation. Furthermore, we delineate the relevant adverse events due to a pulse CS regimen and present a decision tree that can be used when treating MS relapses in clinical practice.

[Risk factors, clinical presentations, prevention, and treatment of corneal graft rejection]

Corneal transplantation is the most common and successful type of allotransplantation surgery. Post-transplant immune response in keratoplasty is less pronounced than that in other transplantation procedures, which is accounted for by anatomical features of the cornea and, also, its low antigenic potential and active immunosuppression. However, the immune privilege of the cornea can be violated by neovascularization, inflammation, or trauma. Patients who require keratoplasty to restore their sight and whose immune privilege is disturbed, fall into a high-risk group and are likely to demonstrate tissue incompatibility and non-transparent engraftment. Two approaches exist as to how graft rejection can be prevented. One of them involves induction of donor-specific tolerance, the other - non-specific suppression of the recipient's immune response. To avoid tissue incompatibility, measures can be taken to restore the immune privilege of the cornea as well as to induce antigen-specific tolerance, which is considered a promising, thought yet experimental, area of modern transplantology. In clinical practice, one pays most attention to improvement of non-specific immune suppression methods based on interfering in the metabolism of immunocompetent cells. Thus, timely prescriptions and proper immunosuppressive tactics with account to possible risk factors determine the outcome in high-risk patients undergoing corneal transplantation surgery.

Corneal Allograft Rejection: Immunopathogenesis to Therapeutics

Corneal transplantation is among the most successful solid organ transplants. However, despite low rejection rates of grafts in the ‘low-risk’ setting, rejection can be as high as 70% when grafted into ‘high-risk’ recipient beds. Under normal homeostatic conditions, the avascular cornea provides a unique environment that facilitates immune and angiogenic privilege. An imbalance in pro-inflammatory, angiogenic and lymphangiogenic mediators leads to a breakdown in corneal immune privilege with a consequent host response against the donor graft. Recent developments in lamellar and endothelial keratoplasties have reduced the rates of graft rejection even more, while providing improved visual outcomes. The corneal layer against which an immune response is initiated, largely determines reversibility of the acute episode. While epithelial and stromal graft rejection may be treated with topical corticosteroids with higher success, acute endothelial rejection mandates a more aggressive approach to therapy due to the lack of regenerative capacity of this layer. However, current immunosuppressive regimens come with the caveat of ocular and systemic side effects, making prolonged aggressive treatment undesirable. With the advent of biologics, efficacious therapies with a superior side effect profile are on the horizon. In our review we discuss the mediators of ocular immune privilege, the roles of cellular and molecular immune players in graft rejection, with a focus on human leukocyte antigen and antigen presenting cells. Furthermore, we discuss the clinical risk factors for graft rejection and compare rates of rejection in lamellar and endothelial keratoplasties to traditional penetrating keratoplasty. Lastly, we present the current and upcoming measures of therapeutic strategies to manage and treat graft rejection, including an overview of biologics and small molecule therapy.

Corticosteroids shift the Toll-like receptor response pattern of primary-isolated murine liver cells from an inflammatory to an anti-inflammatory state

OBJECTIVE

Only little is known about the mechanisms of action of corticosteroids in the treatment of inflammatory liver diseases. As there is increasing evidence that stimulation of the innate immune system plays an important pathogenetic role in these conditions, we hypothesized that steroids may interfere with the activation of the Toll-like receptor (TLR) system of the liver.

METHODS

To test this hypothesis, murine non-parenchymal liver cells (Kupffer cells, liver sinusoidal endothelial cells) and primary hepatocytes were stimulated with TLR 1-9 ligands in the presence or absence of dexamethasone. Expression of pro- and anti-inflammatory cytokines was determined by quantitative reverse transcription-PCR or ELISA, respectively. Nuclear factor 'kappa-light-chain-enhancer' of activated B-cells (NF-κB) activation was assessed by western blot analysis.

RESULTS

TLR agonists induced the expression of pro- [tumor necrosis factor-α (TNF-α), IL-6, IL-1β, IFN-β] and anti-inflammatory cytokines [IL-10, transforming growth factor-β (TGF-β)], which was differentially modulated by steroid treatment. TNF-α and IL-6 expression was suppressed by dexamethasone, while IL-10 but not TGF-β was enhanced after TLR stimulation. IFN-β production induced by TLR 4 agonists but not TLR 3 agonists was inhibited by dexamethasone. TLR expression itself was down-regulated by steroid treatment in a cell type-specific manner. These effects were associated with suppression of the TLR-mediated activation of NF-κB.

CONCLUSIONS

TLR signaling is modulated by corticosteroids in a cell type-specific fashion resulting in down-regulation of TLR expression, suppression of pro-inflammatory and up-regulation of anti-inflammatory cytokines. This represents an as yet unknown mechanism of action for corticosteroids that may at least in part explain their therapeutic effects in inflammatory liver diseases.