An ancestral molecular response to nanomaterial particulates.

The varied transcriptomic response to nanoparticles has hampered the understanding of the mechanism of action. Here, by performing a meta-analysis of a large collection of transcriptomics data from various engineered nanoparticle exposure studies, we identify common patterns of gene regulation that impact the transcriptomic response. Analysis identifies deregulation of immune functions as a prominent response across different exposure studies. Looking at the promoter regions of these genes, a set of binding sites for zinc finger transcription factors C2H2, involved in cell stress responses, protein misfolding and chromatin remodelling and immunomodulation, is identified. The model can be used to explain the outcomes of mechanism of action and is observed across a range of species indicating this is a conserved part of the innate immune system.

c-Jun N-terminal kinase 1 is deleterious to the function and survival of murine pancreatic islets.

AIMS/HYPOTHESIS: Inhibition of c-jun N-terminal kinase (JNK) favours pancreatic islet function and survival. Since two JNK isoforms are present in the pancreas (JNK1 and JNK2), we addressed their specific roles in experimental islet transplantation. METHODS: C57BL/6J (wild-type [WT]), Jnk1 (also known as Mapk8)(-/-) and Jnk2 (also known as Mapk9)(-/-) mice were used as donor/recipients in a syngeneic islet transplantation model. Islet cell composition, function, viability, production of cytokines and of vascular endothelial growth factor (VEGF) were also studied in vitro. RESULTS: Jnk1 ( -/- ) islets secreted more insulin in response to glucose and were more resistant to cytokine-induced cell death compared with WT and Jnk2 (-/-) islets (p < 0.01). Cytokines reduced VEGF production in WT and Jnk2 (-/-) but not Jnk1 ( -/- ) islets; VEGF blockade restored Jnk1 ( -/- ) islet susceptibility to cytokine-induced cell death. Transplantation of Jnk1 ( -/- ) or WT islets into WT recipients made diabetic had similar outcomes. However, Jnk1 ( -/- ) recipients of WT islets had shorter time to diabetes reversal (17 vs 55 days in WT, p = 0.033), while none of the Jnk2 (-/-) recipients had diabetes reversal (0% vs 71% in WT, p = 0.0003). Co-culture of WT islets with macrophages from each strain revealed a discordant cytokine production. CONCLUSIONS/INTERPRETATION: We have shown a deleterious effect of JNK2 deficiency on islet graft outcome, most likely related to JNK1 activation, suggesting that specific JNK1 blockade may be superior to general JNK inhibition, particularly when administered to transplant recipients.

Failure to phosphorylate AKT in podocytes from mice with early diabetic nephropathy promotes cell death.

Loss of podocytes by apoptosis characterizes the early stages of diabetic nephropathy. To examine its mechanism we studied glomeruli and podocytes isolated from db/db mice with early diabetic nephropathy and albuminuria. Phosphorylation of AKT (protein kinase B, a key survival protein) was found to be lower in the glomeruli of 12 week old db/db compared to db/+ mice. In vitro, insulin phosphorylated AKT solely in podocytes from db/+ mice. Serum deprivation and exposure to tumor necrosis factor-alpha significantly compromised cell viability in podocytes from db/db but not from db/+ mice, and this was associated with a significant decrease in AKT phosphorylation. Inhibition of AKT was necessary to achieve the same degree of cell death in db/+ podocytes. Our study shows that podocyte inability to respond to insulin and susceptibility to cell death may partially account for the decreased podocyte number seen in early diabetic nephropathy.

Inhibition of c-jun N terminal kinase (JNK) improves functional beta cell mass in human islets and leads to AKT and glycogen synthase kinase-3 (GSK-3) phosphorylation.

AIMS/HYPOTHESIS: Activation of c-jun N-terminal kinase (JNK) has been described in islet isolation and engraftment, making JNK a key target in islet transplantation. The objective of this study was to investigate if JNK inhibition with a cell-permeable TAT peptide inhibitor (L-JNKI) protects functional beta cell mass in human islets and affects AKT and its substrates in islet cells. METHODS: The effect of L-JNKI (10 micromol/l) on islet count, mitochondrial membrane potential, glucose-stimulated insulin release and phosphorylation of both AKT and its substrates, as well as on reversal of diabetes in immunodeficient diabetic Nu/Nu mice was studied. RESULTS: In vitro, L-JNKI reduced the islet loss in culture and protected from cell death caused by acute cytokine exposure. In vivo, treatment of freshly isolated human islets and diabetic Nu/Nu mice recipients of such islets resulted in improved functional beta cell mass. We showed that L-JNKI activates AKT and downregulates glycogen synthase kinase-3 beta (GSK-3B) in human islets exposed to cytokines, while other AKT substrates were unaffected, suggesting that a specific AKT/GSK-3B regulation by L-JNKI may represent one of its mechanisms of cytoprotection. CONCLUSIONS/INTERPRETATION: In conclusion, we have demonstrated that targeting JNK in human pancreatic islets results in improved functional beta cell mass and in the regulation of AKT/GSK3B activity.