Polyclonal Immunotactoid Glomerulopathy Associated with Monoclonal Gammopathy of IgM Type and Underlying Plasmacellular Disease: Successful Treatment with Rituximab Alone.

Immunotactoid glomerulopathy (ITG) occurs infrequently and is characterized by organized IgG containing deposits. It most usually manifests as a concomitant disease of a broad spectrum of oncologic entities. We here present an exceptional case of ITG without glomerular light chain restriction secondary to a IgM kappa type monoclonal gammopathy of undetermined significance. Due to nephrotic syndrome and deterioration of kidney function a rituximab monotherapy was initiated without targeting the plasmacellular augmentation, which was confirmed as the underlying process. The treatment led to a long-term improvement of proteinuria and stabilization of glomerular filtration rate. Its therapeutic effect has to be attributed to immunomodulatory capacities and targeting of podocytes rather than to be interpreted as directed against a bone marrow or glomerular clone. We conclude that rituximab therapy may be a valuable part of the therapeutic options in ITG irrespective of the underlying oncologic entity.

Involvement of reactive oxygen species in cardiotrophin-1-induced proliferation of cardiomyocytes differentiated from murine embryonic stem cells.

Cardiotrophin-1 (CT-1) is a cytokine that is involved in the growth and survival of cardiac cells. In the present study, we demonstrate that treatment of embryoid bodies grown from pluripotent murine embryonic stem (ES) cells with CT-1 significantly stimulated cardiomyogenesis and increased nuclear expression of the proliferation marker Ki-67. The increase in Ki-67 expression was inhibited upon pretreatment with the free radical scavenger vitamin E, indicating a role for reactive oxygen species (ROS) in the signaling cascade. CT-1 treatment of cardiac cells raised intracellular ROS in ES cell-derived cardiomyocytes. ROS were presumably generated by an NADPH-oxidase since ROS generation was down-regulated upon preincubation with the NADPH-oxidase inhibitor diphenylen iodonium chloride (DPI) and LY294002, which inhibits phosphatidylinositol 3 kinase (PI3-kinase). CT-1 activated nuclear factor-kappaB (NF-kappaB) and induced phosphorylation of the Janus kinase signal transducer-2 (Jak-2), the signal transducer and activator of transcription-3 (STAT-3) as well as the extracellular signal-regulated kinase 1,2 (ERK1/2). STAT-3 and ERK1/2 phosphorylation as well as NF-kappaB activation were inhibited by pretreatment with the Jak-2 antagonist AG490, the ERK1/2 inhibitor PD98059, the free radical scavenger vitamin E, the NADPH-oxidase inhibitor DPI, as well as by LY294002. PD98059 failed to inhibit Jak-2 phosphorylation, indicating that the ERK and the Jak/STAT signaling cascade interact on a level downstream of Jak-2. It is concluded that CT-1 stimulates the proliferation of ES cell-derived cardiomyocytes by signaling pathways that involve ROS as signaling molecules in the signal transduction cascade.