A nanoparticle-based approach targeting ion channels for the treatment of Lupus nephritis

Lupus nephritis (LN) occurs in up to 60% of patients with systemic lupus erythematosus (SLE) and it remains the predominant cause of morbidity and mortality. Current available therapies for SLE have serious side effects and limited efficacy. Our research aims to develop a novel therapy for SLE with improved efficacy and minimal side effects. SLE is in large part driven by hyperactive T cells, which present with multiple defects including increased INFγ, chemokine receptors and CD40L that exacerbate tissue infiltration, inflammation and B cell stimulation. Kv1.3 channels regulate the Ca2+ signaling necessary for these effector functions. We have developed lipid nanoparticles that selectively target memory T (TM) cells and reduce their hyper-functionality by downregulating Kv1.3 via siRNAs (Kv1.3-NPs). Our in-vitro data showed that Kv1.3-NPs suppressed Ca2+ signaling, CD40L expression and IFNγ release selectively in TM cells. To demonstrate therapeutic efficacy of the Kv1.3-NPs we have developed a humanized mouse model of LN by engrafting peripheral blood mononuclear cells (PBMCs) from LN patients into immune-deficient NSG mice. Kidneys of these mice were highly infiltrated with human CD3+ T cells and these cells produced elevated IFNγ. Furthermore, these mice demonstrated a lower survival compared to control mice engrafted with PBMCs from healthy donors. Lastly, we tested the efficacy of the Kv1.3-NPs. We found that LN mice engrafted with PBMCs pretreated in-vitro with Kv1.3-NPs survived longer than mice engrafted with PBMCs pretreated with scramble RNA-NPs. We also found that Kv1.3-NPs were selectively delivered in-vivo into TM cells of humanized mice. Overall, these data support the potential therapeutic value of Kv1.3-NPs.

Differential calcium signaling and Kv1.3 trafficking to the immunological synapse in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) T cells exhibit several activation signaling anomalies including defective Ca(2+) response and increased NF-AT nuclear translocation. The duration of the Ca(2+) signal is critical in the activation of specific transcription factors and a sustained Ca(2+) response activates NF-AT. Yet, the distribution of Ca(2+) responses in SLE T cells is not known. Furthermore, the mechanisms responsible for Ca(2+) alterations are not fully understood. Kv1.3 channels control Ca(2+) homeostasis in T cells. We reported a defect in Kv1.3 trafficking to the immunological synapse (IS) of SLE T cells that might contribute to the Ca(2+) defect. The present study compares single T cell quantitative Ca(2+) responses upon formation of the IS in SLE, normal, and rheumatoid arthritis (RA) donors. Also, we correlated cytosolic Ca(2+) concentrations and Kv1.3 trafficking in the IS by two-photon microscopy. We found that sustained [Ca(2+)](i) elevations constitute the predominant response to antigen stimulation of SLE T cells. This defect is selective to SLE as it was not observed in RA T cells. Further, we observed that in normal T cells termination of Ca(2+) influx is accompanied by Kv1.3 permanence in the IS, while Kv1.3 premature exit from the IS correlates with sustained Ca(2+) responses in SLE T cells. Thus, we propose that Kv1.3 trafficking abnormalities contribute to the altered distribution in Ca(2+) signaling in SLE T cells. Overall these defects may explain in part the T cell hyperactivity and dysfunction documented in SLE patients.

Altered dynamics of Kv1.3 channel compartmentalization in the immunological synapse in systemic lupus erythematosus

Aberrant T cell responses during T cell activation and immunological synapse (IS) formation have been described in systemic lupus erythematosus (SLE). Kv1.3 potassium channels are expressed in T cells where they compartmentalize at the IS and play a key role in T cell activation by modulating Ca(2+) influx. Although Kv1.3 channels have such an important role in T cell function, their potential involvement in the etiology and progression of SLE remains unknown. This study compares the K channel phenotype and the dynamics of Kv1.3 compartmentalization in the IS of normal and SLE human T cells. IS formation was induced by 1-30 min exposure to either anti-CD3/CD28 Ab-coated beads or EBV-infected B cells. We found that although the level of Kv1.3 channel expression and their activity in SLE T cells is similar to normal resting T cells, the kinetics of Kv1.3 compartmentalization in the IS are markedly different. In healthy resting T cells, Kv1.3 channels are progressively recruited and maintained in the IS for at least 30 min from synapse formation. In contrast, SLE, but not rheumatoid arthritis, T cells show faster kinetics with maximum Kv1.3 recruitment at 1 min and movement out of the IS by 15 min after activation. These kinetics resemble preactivated healthy T cells, but the K channel phenotype of SLE T cells is identical to resting T cells, where Kv1.3 constitutes the dominant K conductance. The defective temporal and spatial Kv1.3 distribution that we observed may contribute to the abnormal functions of SLE T cells.