The Influence of Immunosuppressive Drugs on T- and B-cell Apoptosis via p53-Mediated Pathway In Vitro and In Vivo

Suppressive Effect of 1α,25-Dihydroxyvitamin D3 on Th17-Immune Responses in Kidney Transplant Recipients With Tacrolimus-Based Immunosuppression

BACKGROUND

The aim of this study was to investigate whether 1α,25-dihydroxyvitamin D3 can regulate Th17-related immune responses in kidney transplant recipients (KTRs) being treated with tacrolimus (Tac)-based immunosuppression.

METHODS

First, we evaluated the effect of 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) on Th17-immune responses in an in vitro study using peripheral blood mononuclear cells (PBMCs) from healthy volunteers or KTRs. Next, we investigated mammalian target of rapamycin/STAT3 signaling as a mechanism by which 1,25(OH)2D3 exerted its effect on T cells using the Jurkat cell line. Third, we investigated Th17-cytokine levels or Th17 cell percentage in PBMCs according to the serum 25-hydroxyvitamin D (25(OH)D) level in 81 KTRs, and we performed a prospective study to assess whether 1,25(OH)2D3 (calcitriol) treatment decreased Th17 cytokine levels (IL-17, IL-22) in 42 KTRs.

RESULTS

In the in vitro study, we observed that the addition of 1,25(OH)2D3 to Tac significantly inhibited the appearance of IL-17-positive cells in culture. The expression of IL-17 and IL-22 messenger RNA in PBMCs was also decreased by the addition of 1,25(OH)2D3. In the Jurkat cell line, the mTOR/STAT3 pathway was further downregulated with the addition of 1,25(OH)2D3 to Tac. In the 81 KTRs, the 25(OH)D level was inversely correlated with the Th17 cytokine levels or the proportion of Th17 cell out of CD4 T cells. Treatment with calcitriol for 6 months significantly decreased Th17 cytokine levels compared with the baseline values in another 42 KTRs.

CONCLUSIONS

Treatment with 1,25(OH)2D3 may have immunologic benefits by effectively suppressing the Th17-related immune responses in KTRs on Tac-based immunosuppression.

Immunomodulatory Effects of Different Cellular Therapies of Bone Marrow Origin on Chimerism Induction and Maintenance Across MHC Barriers in a Face Allotransplantation Model

Many more patients would benefit from vascularized composite allotransplantation if less toxic and safer immunosuppressive protocols will become available. Tolerance induction protocols with donor cells co-transplantation are one of the promising pathways to reduce maintenance immunosupressive regimens. We investigated the role of donor bone marrow cells (BMC), mesenchymal stromal cells (MSC) and in vivo created chimeric cells (CC) used as supportive therapies in a fully MHC-mismatched rat face transplantation model. Twenty-four fully MHC-mismatched hemiface transplantations were performed between ACI (RT1(a)) donors and Lewis (RT1(l)) recipients under combined seven-day immunosuppressive regimen of anti-αβ-T-cell receptor (TCR) monoclonal antibody and cyclosporin A. We studied four experimental groups-group 1: no cellular therapy; group 2: supportive therapy with BMC; group 3: supportive therapy with MSC; group 4: supportive therapy with CC generated in a primary chimera. We evaluated clinical and histological rejection grades, transplanted cells migration, donor-specific chimerism in the peripheral blood and bone marrow compartments, and CD4(+)/CD25(+) T-cell levels. Face allograft rejection was observed at 26.8 ± 0.6 days post-transplant (PT) in the absence of cellular therapy, at 34.5 ± 1.1 days for group 2, 29.3 ± 0.8 days for group 3, and 30.3 ± 1.38 PT for group 4. The longest survival was observed in allografts supported by co-transplantation of BMC. All support in cellular therapies delayed face allograft rejection by chimerism induction and/or immunomodulatory properties of co-transplanted cells. Survival time was comparable between groups, however, further studies, with different cell dosages, delivery routes and delivery times are required.

Myocyte growth, repair, and oxidative stress following pediatric heart transplantation

Cardiac remodeling is associated with plasma biomarkers of fibrinogenesis, inflammation, and oxidative stress, and upregulation of mitogenic, pro-fibrotic, and apoptotic signaling pathways. Our primary objective was to evaluate biomarker and subcellular myocardial changes in pediatric heart transplant recipients. Fifty-two-week prospective, randomized (tacrolimus, Tac, vs. cyclosporine, CsA), open-label, parallel group study. Serial myocardial biopsies were probed for mitogenic and pro-inflammatory proteins. Plasma biomarkers of oxidative stress (F2α isoprostanes, nitrotyrosine), and inflammation and oxidation (hsCRP and cystatin-C) were measured. Nine of 11 randomized patients completed the study (four Tac, five CsA). Mean levels of F2α isoprostanes, hsCRP, and cystatin-C were maximal at Week 2. Peak activation of all MAP kinases in myocardial tissue was maximal at Week 10; no association was seen with rejection. Cardiac Bax/Bcl-2 levels (index of apoptosis) correlated negatively with F2α isoprostanes at Week 2 (r = -0.88) and with hsCRP at Week 52 (r = -0.67). At Week 52, hsCRP levels correlated positively with molecular indices of cardiac cell growth. We found evidence of systemic and myocardial oxidative damage and inflammation early posttransplant, which may be related to the remodeling process. Further study is needed to better understand the cardiac and systemic repair processes following pediatric heart transplantation.

Mycophenolic acid differentially impacts B cell function depending on the stage of differentiation

Production of pathogenic Abs contributes to disease progression in many autoimmune disorders. The immunosuppressant agent mycophenolic acid (MPA) has shown clinical efficacy for patients with autoimmunity. The goal of these studies was to elucidate the mechanisms of action of MPA on B cells isolated from healthy individuals and autoimmune patients. In this study, we show that MPA significantly inhibited both proliferation and differentiation of primary human B cells stimulated under various conditions. Importantly, MPA did not globally suppress B cell responsiveness or simply induce cell death, but rather selectively inhibited early activation events and arrested cells in the G0/G1 phase of the cell cycle. Furthermore, MPA blocked expansion of both naive and memory B cells and prevented plasma cell (PC) differentiation and Ab production from healthy controls and individuals with rheumatoid arthritis. Finally, whereas MPA potently suppressed Ig secretion from activated primary B cells, terminally differentiated PCs were not susceptible to inhibition by MPA. The target of MPA, IMPDH2, was found to be downregulated in PCs, likely explaining the resistance of these cells to MPA. These results suggest that MPA provides benefit in settings of autoimmunity by directly preventing activation and PC differentiation of B cells; however, MPA is unlikely to impact autoantibody production by preexisting, long-lived PCs.

In rat renal fibroblasts, mycophenolic acid inhibits proliferation and production of the chemokine CCL2, stimulated by tumour necrosis factor-alpha

BACKGROUND AND PURPOSE

Renal fibroblasts play a pivotal role in the development of tubulointerstitial fibrosis, a condition highly predictive of progression towards end-stage renal disease. The present study investigated the anti-mitogenic and anti-inflammatory effects of an inhibitor of inosine monophosphate dehydrogenase, mycophenolic acid (MPA) and the mechanisms underlying its action in normal rat kidney fibroblasts (49F cells).

EXPERIMENTAL APPROACH

Proliferation of 49F cells was studied by tetrazole 3-(4, 5-dimethylthiazol-2-yl-)-2,5-diphenyltetrazolium bromide (MTT) test, bromodeoxyuridine incorporation and flow cytometry. The cyclins, tumour suppressor genes and phospho-mitogen-activated protein kinases (MAPKs) were semiquantified by immunoblotting. Apoptosis was measured by quantifying the fragmented DNA and the activity of caspase 3. The monocyte chemokine CCL2 was measured by ELISA. The mRNA expression of CCL2 was measured by real-time PCR.

KEY RESULTS

Mycophenolic acid dose-dependently inhibited steady-state proliferation of 49F cells by up-regulation of p21, p27 and p53, in association with a decrease in cyclins D2 and E. Treatment with MPA also triggered apoptosis of 49F cells by activating the caspase 3 cascade. Furthermore, MPA attenuated tumour necrosis factor-alpha-induced CCL2 expression through down-regulation of p38 MAPK, but not that of ERK1/2 or JNK.

CONCLUSIONS AND IMPLICATIONS

The anti-mitogenic and anti-inflammatory effects of MPA were mediated by up-regulation of cell cycle inhibitors and pro-apoptotic signals, and by suppression of p38 MAPK pathway respectively. This dual effect of MPA may form the rationale for animal or clinical trials for the treatment of fibrotic renal diseases.

Tacrolimus-induced apoptotic signal transduction pathway

Tacrolimus (FK506) has been widely used as an immunosuppressant. We examined the effects of FK506 on expression of apoptotic signal transduction pathway proteins of Jurkat human T lymphocytes. We investigated the effects of FK506 on apoptosis, cell viability, caspase family protein activity, Western blotts of Bcl-2, Bak, Fas, Fas-L, CDK4, and cyclin D1, as well as reactive oxygen species (ROS) generation and mitochondrial membrane potential transition. Cells were cultured in the presence or absence of FK506. Flow cytometric analysis was performed after staining with propidium iodide. Viability of Jurkat cells was decreased by the addition of FK506 in dose- and time- dependent manner. FK506-induced cytotoxicity was characterized by G0/G1 phase cell cycle arrest. FK506-induced cell death was confirmed by apoptosis characterized by nuclear fragmentation and caspase-3 protease activation. FK506 induced no change in catalytic activity of caspase-6, -8, and -9 proteases. No change in expression of Bcl-2 protein was noted but we confirmed increased expression of Bak protein. No changes of expressions of Fas and Fas-L were seen. Increased expressions of CDK4 and cyclin D1 were identified. In addition, pharmacological scavenging study of ROS, including H2O2, revealed that cytotoxicity was achieved by generation of ROS, which might modulate Bak protein expression and mitochondrial dysfunction. In conclusion, FK506-induced cell death was apoptotic, characterized by nuclear fragmentation and caspase-3 activation. FK506 induced G0/G1 phase cell cycle arrest via expression of CDK4 and cyclin D1. Apoptosis was also achieved by generation of H2O2, which modulated Bak protein expression and mitochondrial dysfunction.

Cytomics and nanobioengineering

The finding that an individual's genome differs as much as by many million variants from that of the human reference assembly diminished the great enthusiasm that every disease could be predicted based on nucleotide polymorphisms. Even individual cells of an organ may be specifically equipped to perform specific tasks and that the information of individual cells in a cell system is key information to understand function or dysfunction. Therefore, cytomics received great attention during the last years as it allows to quantitatively and qualitatively analyzing great number of individual cells, cell constituents, and of their intracellular and functional interactions in a cellular system and also giving the concept of analysis of these data.Exhaustive data extraction from multiparametric assays and multiple tests are the prerequisite for prediction of drug toxicity. Cytomics, as novel approach for unsupervised data analysis give a chance to find the most predictive parameters, which describe best the toxicity of a chemical. Cytomics is intrinsically connected to drug development and drug discovery.Focused on small structures, nanobioengineering is the ideal partner of cytomics, the systems biological discipline for cell population analysis. Realizing the idea "from the molecule to the patient" develops and offers chemical compounds, proteins, and other biomolecules, cells as well as tissues as instruments and products for a wide variety of biotechnological and biomedical applications.The integrative nanobioengineering combining different disciplines of nanotechnology will promote the development of innovative therapies and diagnostic methods. It can improve the precision of the measurements with focus on single cell analysis. By nanobioengineering and whole body imaging techniques, cytomics covers the field from molecules through bacterial cells, eukaryotic tissues, and organs to small animal live analysis. Toxicological testing and medical drug development are currently strongly broadening. It harbors the promise to substantially impact on various fields of biomedicine, drug discovery, and predictive medicine.As the number of scientific data is rising exponentially, new data analysis tools and strategies like cytomics and nanobioengineering take a lead and get closer to application. Bionanoengineering may strongly support the quantitative data supply, thus strengthening the rational for cytomics approach.