Pathogenic T cells in murine lupus exhibit spontaneous signaling activity through phosphatidylinositol 3‐kinase and mitogen‐activated protein kinase pathways

Abstract

Objective. To determine the activation status of two cytoplasmic signaling pathways, phosphatidylinositol 3-kinase (PI 3-kinase) and the mitogen-activated protein kinase (MAPK) family.Methods. We studied the pathogenic CD4؉ T cells that drive disease in the parent-into-F 1 mouse model of lupus-like chronic graft-versus-host disease (GVHD). We determined immunoprecipitated kinase activity for PI 3-kinase and MAPK members ( Results. Compared with negative controls, unfractionated splenocyte kinase activity from chronic GVHD mice was significantly increased for PI 3-kinase and JNK-1, but not for Raf-1, p38 MAPK, or ERK-1. Increased PI 3-kinase and JNK-1 activity was also seen in acute GVHD splenocytes, as was increased Raf-1 and p38 MAPK activity. The pattern of increased PI 3-kinase and JNK-1 activity seen in unfractionated chronic GVHD splenocytes was also seen in isolated donor, but not host, CD4؉ T cells from chronic GVHD mice, indicating that donor CD4؉ T cell signaling activity accounted for at least a portion of the activity observed in unfractionated splenocytes. Increased ERK-1 activity was not seen in either donor or host CD4؉ T cells. This pattern of cytoplasmic signaling pathway in donor CD4؉ T cells was associated with increased T cell receptor membrane signaling activation (Lck and Fyn phosphorylation) and increased transcription activation (phosphorylation of inhibitor of nuclear factor B), confirming the biologic significance of these observations. Conclusion. The pathogenic T cells driving disease in this murine model exhibit activation in the form of spontaneous cytoplasmic signaling pathway activity that can be detected without in vitro restimulation and involves a T cell-specific (PI 3-kinase) and a nonspecific stress/cytokine pathway (JNK-1). These results raise the possibility that a full characterization of the signaling pathways active in pathogenic lupus T cells might lead to new therapeutic targets.

Class IB-Phosphatidylinositol 3-Kinase (PI3K) Deficiency Ameliorates IA-PI3K-Induced Systemic Lupus but Not T Cell Invasion

“…Enhanced I A -PI3K activation causes lupus (3)(4)(5). Moreover, endogenous PI3K activation was observed in a graft-vs-host-induced murine systemic lupus model (20) and in lupus-prone MRL/lpr mice (21). Our preliminary data suggest that PI3K activity is also increased in human SLE T cells (Ͼ75% of patients, n ϭ 17, in progress).…”

Anti‐DNA Ig peptides promote Treg cell activity in systemic lupus erythematosus patients

“…To study T cells, short-term cultures were chosen over freshly isolated peripheral blood cells because T cells in SLE patients may be desensitized from repeated autoantigenic stimulation in vivo and from steroid therapy (32), whereas the activity of lupus T cells can reemerge after resting (33,34). Ficoll gradient-separated peripheral blood mononuclear cells (PBMCs) from patients with SLE and from healthy subjects were cultured under identical conditions at a concentration of 1 ϫ 10 6 /ml in 48-well plates in AIM-V (Invitrogen, Carlsbad, CA) with 20 units/ml IL-2, 10 ng/ml IL-7, and 10 ng/ml IL-15 (to prevent the death of memory T cells) (32).…”

Shared signaling networks active in B cells isolated from genetically distinct mouse models of lupus

“…These predictions warrant further experimental verification. Using the graft-versus-host disease model in which a disease resembling lupus is engineered in F1 recipients following injection of allomismatched parental T cells, Niculescu et al demonstrated strong upregulation of PI3K, p38 MAPK , and JNK-1 activity in donor CD4 + T cells (35). Increased spontaneous PI3K and JNK activity has also been documented in T cells from human SLE patients (35).…”

“…Using the graft-versus-host disease model in which a disease resembling lupus is engineered in F1 recipients following injection of allomismatched parental T cells, Niculescu et al demonstrated strong upregulation of PI3K, p38 MAPK , and JNK-1 activity in donor CD4 + T cells (35). Increased spontaneous PI3K and JNK activity has also been documented in T cells from human SLE patients (35). Rapoport et al demonstrated constitutive upregulation of the MAPKs in lymphocytes from SLE patients, associated with downregulation of early p21 Ras signaling (36).…”