Mitochondrial-targeted curcumin inhibits T-cell activation via Nrf2 and inhibits graft-versus-host-disease in a mouse model.

Anti-inflammatory and immune suppressive agents are required to moderate hyper-activation of lymphocytes under disease conditions or organ transplantation. However, selective disruption of mitochondrial redox has not been evaluated as a therapeutic strategy for suppression of T-cell-mediated pathologies. Using mitochondrial targeted curcumin (MitoC), we studied the effect of mitochondrial redox modulation on T-cell responses by flow cytometry, transmission electron microscopy, transcriptomics, and proteomics, and the role of Nrf2 was studied using Nrf2- /- mice. MitoC decreased mitochondrial TrxR activity, enhanced mitochondrial ROS (mROS) production, depleted mitochondrial glutathione, and suppressed activation-induced increase in mitochondrial biomass. This led to suppression of T-cell responses and metabolic reprogramming towards Treg differentiation. MitoC induced nuclear translocation and DNA binding of Nrf2, leading to upregulation of Nrf2-dependent genes and proteins. MitoC-mediated changes in mitochondrial redox and modulation of T-cell responses are abolished in Nrf2- /- mice. Restoration of mitochondrial thiols abrogated inhibition of T-cell responses. MitoC suppressed alloantigen-induced lymphoblast formation, inflammatory cytokines, morbidity, and mortality in acute graft-versus-host disease mice. Disruption of mitochondrial thiols but not mROS increase inculcates an Nrf2-dependent immune-suppressive disposition in T cells for the propitious treatment of graft-versus-host disease.

Pre-clinical evaluation of an innovative oral nano-formulation of baicalein for modulation of radiation responses.

There is an unmet medical need for non-toxic and effective radiation countermeasures for prevention of radiation toxicity during planned exposures. We have earlier shown that intraperitoneal administration of baicalein (BCL) offers significant survival benefit in animal model. Safety, tolerability, pharmacokinetics (PK) and pharmacodynamics of baicalein has been reported in pre-clinical model systems and also in healthy human volunteers. However, clinical translation of baicalein is hindered owing to poor bioavailability due to lipophilicity. In view of this, we fabricated and characterized in-situ solid lipid nanoparticles of baicalein (SLNB) with effective drug entrapment and release kinetics. SLNB offered significant protection to murine splenic lymphocytes against 4 Gy ionizing radiation (IR) induced apoptosis. Oral administration of SLNB exhibited ~70% protection to mice against whole body irradiation (WBI 7.5 Gy) induced mortality. Oral relative bioavailability of BCL was enhanced by over ~300% after entrapment in the SLNB as compared to BCL. Oral dosing of SLNB resulted in transient increase in neutrophil abundance in peripheral blood. Interestingly, we observed that treatment of human lung cancer cells (A549) with radioprotective dose of SLNB exhibited radio-sensitization as evinced by decrease in survival and clonogenic potential. Contrary to antioxidant nature of baicalein in normal cells, SLNB treatment induced significant increase in cellular ROS levels in A549 cells probably due to higher uptake and inhibition of TrxR. Thus, a pharmaceutically acceptable SLNB exhibited improved bioavailability, better radioprotection to normal cells and sensitized cancer cells to radiation induced killing as compared to BCL suggesting its possible utility as an adjuvant during cancer radiotherapy.

Schisandrin B exhibits anti-inflammatory activity through modulation of the redox-sensitive transcription factors Nrf2 and NF-κB.

Schisandrin B (SB), a dibenzocyclooctadiene derivative isolated from Schisandra chinensis and used commonly in traditional Chinese medicine for the treatment of hepatitis and myocardial disorders, has been recently shown to modulate cellular redox balance. Since we have shown that cellular redox plays an important role in the modulation of immune responses, the present studies were undertaken to study the effects of SB on activation and effector functions of lymphocytes. SB altered the redox status of lymphocytes by enhancing the basal reactive oxygen species levels and altering the GSH/GSSG ratio in lymphocytes. It also induced nuclear translocation of redox sensitive transcription factor Nrf2 and increased the transcription of its dependent genes. SB inhibited mitogen-induced proliferation and cytokine secretion by lymphocytes. SB also significantly inhibited mitogen-induced upregulation of T cell costimulatory molecules and activation markers. It was observed that SB inhibited mitogen-induced phosphorylation of c-Raf, MEK, ERK, JNK, and p38. It suppressed IκBα degradation and nuclear translocation of NF-κB in activated lymphocytes. Anti-inflammatory effects of SB were significantly abrogated by the inhibitors of Nrf2 and HO-1, suggesting the involvement of this pathway. Similar anti-inflammatory effects of SB on lymphocyte proliferation and cytokine secretion were also observed in vivo. To our knowledge, this is the first report showing that the anti-inflammatory effects of SB are mediated via modulation of Nrf2 and NF-κB in lymphocytes.

Vitamin K3 suppressed inflammatory and immune responses in a redox-dependent manner.

Recent investigations suggest that cellular redox status may play a key role in the regulation of several immune functions. Treatment of lymphocytes with vitamin K3 (menadione) resulted in a significant decrease in cellular GSH/GSSG ratio and concomitant increase in the ROS levels. It also suppressed Concanavalin A (Con A)-induced proliferation and cytokine production in lymphocytes and CD4 + T cells in vitro. Immunosuppressive effects of menadione were abrogated only by thiol containing antioxidants. Mass spectrometric analysis showed that menadione directly interacted with thiol antioxidant GSH. Menadione completely suppressed Con A-induced activation of ERK, JNK and NF-κB in lymphocytes. It also significantly decreased the homeostasis driven proliferation of syngeneic CD4 + T cells. Further, menadione significantly delayed graft-vs-host disease morbidity and mortality in mice. Menadione suppressed phytohemagglutinin-induced cytokine production in human peripheral blood mononuclear cells. These results reveal that cellular redox perturbation by menadione is responsible for significant suppression of lymphocyte responses.