Mycophenolate mofetil in animal models of autoimmune disease

Antimetabolite Drugs Exhibit Distinctive Immunomodulatory Mechanisms and Effects on the Intestinal Microbiota in Experimental Autoimmune Uveitis

Purpose

The purpose of this study was to investigate the effect of antimetabolite drugs on T-cell responses and intestinal microbial composition in autoimmune uveitis.

Methods

Experimental autoimmune uveitis (EAU) was induced in C57BL/6J mice treated with 0.00625 mg/mL methotrexate (MTX) or 0.625 mg/mL mycophenolate mofetil (MMF) in drinking water for 4 weeks prior to immunization and 2 weeks thereafter. The effector T cell (Teff) and regulatory T cell (Treg) populations were identified using flow cytometry. The 16S rRNA gene sequencing was applied for gut microbiome characterization. DESeq2 analysis was used to discriminate relative abundances of taxa and PLS-DA to integrate cytometric and microbiome data between groups.

Results

Both MTX and MMF abrogated uveitis in EAU without clinical signs of toxicity as compared to water-fed controls. MTX reduced Teff and Treg expansion in peripheral tissues and eyes. MTX decreased alpha diversity, increased Akkermansia, and reduced Lachnoclostridium abundances. Conversely, MMF enhanced Tregs in the mesenteric lymph node and the eyes. In parallel, MMF increased the gut alpha diversity, including an increased abundance of Lachnospiraceae NK4A136 group and a decreased abundance of Lachnospiraceae UCG-001. A significant congruent correlation among intestinal microbial changes, T-cell responses, and clinical scores was observed for both antimetabolites.

Conclusions

Although MTX and MMF both abrogated uveitis in EAU, they showed different effects on T-cell subsets and the intestinal bacterial composition. This work indicates unique immunomodulation by each drug and is the first to demonstrate potential microbiota-related mechanisms.

Objetivo

Investigar el efecto de los fármacos antimetabolitos sobre las respuestas de células T y la composición microbiana intestinal en la uveítis autoinmune.

Métodos

Se indujo uveítis autoinmune experimental (UAE) en ratones C57BL/6J tratados con 0.00625 mg/ml de metotrexato (MTX) o 0.625 mg/ml de micofenolato mofetilo (MFM) en agua de bebida durante 4 semanas antes de la inmunización y 2 semanas después. Las poblaciones de células T efectoras (Tef) y reguladoras (Treg) se identificaron por citometría de flujo. La caracterización del microbioma intestinal se realizó mediante secuenciación del gen 16S ARNr. El análisis discriminante de abundancias relativas en los taxones se llevó a cabo por DESeq2 y se usó un análisis PLS-DA para integrar los datos microbianos y citométricos entre grupos.

Resultados

MTX y MFM inhibieron la UAE sin signos clínicos de toxicidad comparado con los controles. MTX disminuyó la expansión de Tef y Treg en los tejidos periféricos y oculares. MTX redujo la alfa diversidad, incrementando la abundancia de Akkermansia, y reduciendo la de Lachnoclostridium. En cambio, MFM aumentó los Tregs en el ganglio mesentérico y en los ojos. Paralelamente, MFM aumentó la alfa diversidad, incluyendo un aumento de la abundancia del grupo Lachnospiraceae NK4A136 y un descenso de la de Lachnospiraceae UCG-001. Se observó una correlación congruente significativa, para ambos fármacos, entre los cambios en el microbioma, las respuestas de células T y los grados clínicos de uveítis.

Conclusiones

Aunque ambos, MTX y MFM, suprimieron la UAE, mostraron efectos diferentes sobre los subtipos de células T y sobre la composición del microbioma. Este estudio indica un efecto inmunomodulador único para cada fármaco y es el primero en demostrar potenciales mecanismos relacionados con el microbioma.

Suppression of cGMP-Dependent Photoreceptor Cytotoxicity With Mycophenolate Is Neuroprotective in Murine Models of Retinitis Pigmentosa

Purpose

To determine the effect of mycophenolate mofetil (MMF) on retinal degeneration on two mouse models of retinitis pigmentosa.

Methods

Intraperitoneal injections of MMF were administered daily in rd10 and c57 mice starting at postoperative day 12 (P12) and rd1 mice starting at P8. The effect of MMF was assessed with optical coherence tomography, immunohistochemistry, electroretinography, and OptoMotry. Whole retinal cyclic guanosine monophosphate (cGMP) and mycophenolic acid levels were quantified with mass spectrometry. Photoreceptor cGMP cytotoxicity was evaluated with cell counts of cGMP immunostaining.

Results

MMF treatment significantly delays the onset of retinal degeneration and cGMP-dependent photoreceptor cytotoxicity in rd10 and rd1 mice, albeit a more modest effect in the latter. In rd10 mice, treatment with MMF showed robust preservation of the photoreceptors up to P22 with associated suppression of cGMP immunostaining and microglial activation; The neuroprotective effect diminished after P22, but outer retinal thickness was still significantly thicker by P35 and OptoMotry response was significantly better up to P60. Whereas cGMP immunostaining of the photoreceptors were present in rd10 and rd1 mice, hyperphysiological whole retinal cGMP levels were observed only in rd1 mice.

Conclusions

Early treatment with MMF confers potent neuroprotection in two animal models of RP by suppressing the cGMP-dependent common pathway for photoreceptor cell death. The neuroprotective effect of MMF on cGMP-dependent cytotoxicity occurs independently of the presence of hyperphysiological whole retinal cGMP levels. Thus our data suggest that MMF may be an important new class of neuroprotective agent that could be useful in the treatment of patients with RP.

New strategies in the management of Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is an acute and usually monophasic, neurological, demyelinating disease. Although most patients have good outcomes without sequelae after conventional plasma exchange and intravenous immunoglobulin therapy, 20% of patients continue to have severe disease and 5% die of their disease. Therefore, there is an obvious need for more acceptable and efficacious therapies. Experimental autoimmune neuritis (EAN) is the classical animal model for GBS. As there is no specific drug for GBS, several drugs targeting the humoral and cellular components of the immune response have been used to treat EAN in the endeavour to find new treatment alternatives for GBS. This review focused on some new strategies for GBS, which have been reported but have not yet been widely used, and on the main drugs which have been investigated in EAN.

Evidence of an anti-inflammatory effect of mycophenolate mofetil in a murine model of pleurisy

A promising therapeutic approach to reducing inflammation is to inhibit the production of proinflammatory cytokines (e.g., tumor necrosis factor alpha [TNF-α], interleukin 1 beta [IL-1β], vascular endothelial growth factor alpha (VEGF-α), and, as shown more recently, interleukin-17 [IL-17]). In the present study, the authors have demonstrated the anti-inflammatory effects of mycophenolate mofetil (MMF) in in vivo experiments and have investigated the mechanism of action underlying those effects. Oral administration of MMF significantly inhibited leukocyte influx during the first (4 hours) and second (48 hours) phases of inflammation in a mouse model of pleurisy caused by carrageenan (P < .01). As expected, MMF suppressed protein levels of TNF-α, IL-1β, VEGF-α, and IL-17A (P < .01). This inhibitory effect was due to down-regulation of mRNA expression for these proinflammatory cytokines (P < .01). These results provide evidence of MMF-mediated inhibition of proinflammatory cytokines, and these anti-inflammatory effects are assumed to result mainly from the inhibition of the synthesis and release of TNF-α, IL-1β, VEGF-α, and IL-17A from activated leukocytes. These findings suggest that MMF might be an applicable therapeutic in the regulation of the inflammatory response-a response in which the humoral system plays a pivotal role.

Prevention of diabetes: effect of mycophenolate mofetil and anti-CD25 on onset of diabetes in the DRBB rat

BACKGROUND

Anti-CD25 and mycophenolate mofetil (MMF) treatment of patients with new-onset diabetes is currently being tested as one of the trials in TrialNet. We tested the effectiveness of MMF and anti-CD25 in preventing autoimmune diabetes in the diabetes-resistant biobreeding (DRBB) rat.

METHODS

Autoimmune diabetes in the DRBB rat was induced with a Treg cell depletion regimen starting at 24-26 d of age. Treatment was started on the first day of the depletion regimen in the following groups: (i) control (vehicle); (ii) MMF 25 mg/kg/d intramuscularly daily for 8 wk; (iii) anti-CD25 0.8 mg/kg/d intraperitoneally 5 d/wk for 3 wk; and (iv) combination of MMF and anti-CD25. In a second set of experiments, treatments were started on day 5 of the depletion regimen (delayed treatment) with groups 1, 3, and 4. Rats that had diabetes-free survival for at least 30 d after the treatment was stopped underwent a second Treg depletion (redepletion).

RESULTS

In each of the three treatment groups (n = 10/group), onset of diabetes was delayed or prevented in 20, 40 and 80% in groups 2, 3, and 4, respectively. After redepletion, diabetes-free survival was unchanged in group 2 and decreased to 10 and 30% in groups 3 and 4, respectively. With delayed treatment, groups 3 and 4 had 33 and 50% diabetes-free survival that decreased to 0 and 33% after redepletion.

SUMMARY

MMF and anti-CD25 alone or in combination are effective in delaying and preventing diabetes in the DRBB rat especially if treatment is started before stimulation and expansion of the autoreactive T cells.