Retinitis pigmentosa comprises a group of inherited retinal photoreceptor degenerations that lead to progressive loss of vision. Although in most cases rods, but not cones, harbor the deleterious gene mutations, cones do die in this disease, usually after the main phase of rod cell loss. Rod photoreceptor death is characterized by apoptotic features. In contrast, the mechanisms and features of subsequent nonautonomous cone cell death remain largely unknown. In this study, we show that receptor-interacting protein (RIP) kinase mediates necrotic cone cell death in rd10 mice, a mouse model of retinitis pigmentosa caused by a mutation in a rod-specific gene. The expression of RIP3, a key regulator of programmed necrosis, was elevated in rd10 mouse retinas in the phase of cone but not rod degeneration. Although rd10 mice lacking Rip3 developed comparable rod degeneration to control rd10 mice, they displayed a significant preservation of cone cells. Ultrastructural analysis of rd10 mouse retinas revealed that a substantial fraction of dying cones exhibited necrotic morphology, which was rescued by Rip3 deficiency. Additionally, pharmacologic treatment with a RIP kinase inhibitor attenuated histological and functional deficits of cones in rd10 mice. Thus, necrotic mechanisms involving RIP kinase are crucial in cone cell death in inherited retinal degeneration, suggesting the RIP kinase pathway as a potential target to protect cone-mediated central and peripheral vision loss in patients with retinitis pigementosa.R etinitis pigmentosa (RP) refers to a group of inherited retinal degenerations that affect over one million individuals globally (1). Although vitamin A supplementation and an ω-3 rich diet has been shown to slow down the visual decline in some patients (2), they do not stop the disease progression and irreversible vision loss still ensues for many patients. Vision loss in RP results from photoreceptor cell death and typically begins with loss of night vision (because of rod dysfunction and death), followed by loss of peripheral and central vision because of loss of cones. This cone-mediated dysfunction is the most debilitating aspect of the disease for patients. Molecular genetic studies have identified mutations in more than 50 genes, most expressed exclusively in rod photoreceptors, which are associated with RP. Although rods that harbor the deleterious gene mutations are expected to die, it is still a puzzle why and how cones-that do not harbor deleterious gene mutations-do die subsequent to the rod degeneration phase.Apoptosis and necrosis are two distinct modes of cell death defined by morphological appearance (3). Apoptosis is the bestcharacterized type of programmed cell death, and the caspase family proteases play a central role in the induction of this process (4). Necrosis, which was traditionally thought to be an uncontrolled process of cell death, is now known to also have a regulated component in some instances (5, 6). Two members of the receptor-interacting protein (RIP) kinase family proteins, ...

Abstract. Interactions between inflammatory infiltrates and resident tubular epithelial cells may play important roles in the development of tubulointerstitial fibrosis, by promoting epithelial cell-myofibroblast transdifferentiation (EMT). Human proximal tubular epithelial cells transdifferentiated to myofibroblasts after treatment with activated PBMC conditioned medium. mRNA and protein levels for ␣-smooth muscle actin, collagen I, and fibronectin EDA ϩ (markers for the myofibroblastic phenotype) were increased, whereas those for E-cadherin and cytokeratin 19 (markers for the epithelial phenotype) were decreased. cDNA microarray analysis was used to identify other changes in gene expression that might point to novel molecular mechanisms driving EMT. Of 1176 array genes, 61 demonstrated at least a twofold change at at least two consecutive time points, of the five time points examined (0.5, 4, 8, 16, and 48 h). Of these genes, 59% were upregulated and 41% were downregulated. The array indicated upregulation of expression of the oncostatin M (OSM)-specific receptor ␤ subunit from 4 to 48 h after exposure of kidney epithelial cells to activated PBMC conditioned medium, which contained high levels of OSM. In additional experiments, it was demonstrated that OSM induced EMT. OSM activated the Jak/Stat signaling pathway in epithelial cells, and a specific inhibitor of Jak2 blocked both its phosphorylation after exposure to OSM and the induction of ␣-actin and loss of cytokeratin 19 expression. Therefore, OSM is a novel inducer of EMT and is likely to be one of several cytokines produced by inflammatory infiltrates that contribute to this and subsequent tubulointerstitial fibrosis.

Intravital visualization of autoimmune-induced tissue damage and Treg cell protection shows contact-based immune cell interactions and growth of bystander tissue cells in pancreatic islet grafts.

IntroductionThe engagement of T-cell receptors (TCRs) by antigen (Ag) peptide in conjugation with major histocompatibility complex (MHC) triggers signaling and results in T-cell activation. 1 However, triggering naive T cells requires both TCR-mediated signals and additional costimulatory signals delivered through the interaction of costimulatory receptors on the T cells with their ligands on Ag-presenting cells (APCs). The most important costimulatory receptors are CD28 and lymphocyte function-associated antigen-1 (LFA-1) on T cells, the ligands of which are CD80/86 2 and intercellular adhesion molecule-1 (ICAM-1) 3 on APCs, respectively.During Ag recognition, T cells interact with APCs in a specific configuration where the TCR is accumulated in the center of the interface as c-SMAC (central supramolecular activation cluster), 4 whereas LFA-1 is accumulated in the periphery as peripheral (p)-SMAC. 4 This structure has been designated the immunologic synapse (IS). 5,6 The peripheral localization of the TCR at an early time point is indicative of an immature IS, whereas the central localization of the TCR at a later time is the hallmark of a mature IS. 6 The dynamic rearrangement and accumulation of these molecules to form IS require the engagement of the costimulatory receptor LFA-1 and cytoskeletal rearrangement. 7 LFA-1, 8 a member of the integrin family, is composed of ␣ and ␤ chains and expressed on T cells, binds to the ligand ICAM-1 on APCs, and is important for T-cell activation and proliferation. 9 Blockade of the interaction between LFA-1 and ICAM-1 results in the inhibition of T-cell activation 10 and induces tolerance. 11 LFA-1 is expressed in the inactive and closed form on naive T cells and mediates only weak interactions with ICAMs. 8,12 The stimulation of T cells through TCRs and chemokine receptors generates an "inside-out" signal that leads to the activation of LFA-1 with an open configuration, increasing its affinity for ICAMs. 3 The insideout signals have been shown to involve several molecules, including ADAP (adhesion-and degranulation-promoting adaptor protein), 13, Vav,16 and Rap-1. 17 In T cells from mice deficient in ADAP (ADAP-KO), TCR-induced LFA-1 activation and clustering were impaired. 13,14 In addition to its role in inside-out signaling, ADAP may also play a role in outside-in signaling from integrins, as very late antigen-4 (VLA-4) stimulation resulted in the phosphorylation of ADAP. 18 LFA-1 also induces activation signals that have costimulatory function. LFA-1 engagement induces the activation of mitogen-activated protein kinases (MAPKs), including extracellular signalregulated kinase 1 (Erk1)/Erk2 through the activation of LFA-1-associated cytohesin-1 and Jun, which is mediated by JAB-1 and c-Jun N-terminal kinase (JNK). [19][20][21] The dynamic rearrangement of the actin cytoskeleton plays an important role in T-cell signaling. 22,23 Inhibitors of actin polymerization completely terminate ongoing TCR-stimulated signaling. TCR-mediated changes in the actin cytoskeleton have b...