Tau suppresses microtubule-regulated pancreatic insulin secretion

Tau protein is implicated in the pathogenesis of Alzheimer's disease (AD) and other tauopathies, but its physiological function is in debate. Mostly explored in the brain, tau is also expressed in the pancreas. We further explored the mechanism of tau's involvement in the regulation of glucose-stimulated insulin secretion (GSIS) in islet β-cells, and established a potential relationship between type 2 diabetes mellitus (T2DM) and AD. We demonstrate that pancreatic tau is crucial for insulin secretion regulation and glucose homeostasis. Tau levels were found to be elevated in β-islet cells of patients with T2DM, and loss of tau enhanced insulin secretion in cell lines, drosophila, and mice. Pharmacological or genetic suppression of tau in the db/db diabetic mouse model normalized glucose levels by promoting insulin secretion and was recapitulated by pharmacological inhibition of microtubule assembly. Clinical studies further showed that serum tau protein was positively correlated with blood glucose levels in healthy controls, which was lost in AD. These findings present tau as a common therapeutic target between AD and T2DM.

Sustained subcutaneous delivery of secretome of human cardiac stem cells promotes cardiac repair following myocardial infarction

AIMS

To establish pre-clinical proof of concept that sustained subcutaneous delivery of the secretome of human cardiac stem cells (CSCs) can be achieved in vivo to produce significant cardioreparative outcomes in the setting of myocardial infarction.

METHODS AND RESULTS

Rats were subjected to permanent ligation of left anterior descending coronary artery and randomized to receive subcutaneous implantation of TheraCyte devices containing either culture media as control or 1 × 106 human W8B2+ CSCs, immediately following myocardial ischaemia. At 4 weeks following myocardial infarction, rats treated with W8B2+ CSCs encapsulated within the TheraCyte device showed preserved left ventricular ejection fraction. The preservation of cardiac function was accompanied by reduced fibrotic scar tissue, interstitial fibrosis, cardiomyocyte hypertrophy, as well as increased myocardial vascular density. Histological analysis of the TheraCyte devices harvested at 4 weeks post-implantation demonstrated survival of human W8B2+ CSCs within the devices, and the outer membrane was highly vascularized by host blood vessels. Using CSCs expressing plasma membrane reporters, extracellular vesicles of W8B2+ CSCs were found to be transferred to the heart and other organs at 4 weeks post-implantation. Furthermore, mass spectrometry-based proteomic profiling of extracellular vesicles of W8B2+ CSCs identified proteins implicated in inflammation, immunoregulation, cell survival, angiogenesis, as well as tissue remodelling and fibrosis that could mediate the cardioreparative effects of secretome of human W8B2+ CSCs.

CONCLUSIONS

Subcutaneous implantation of TheraCyte devices encapsulating human W8B2+ CSCs attenuated adverse cardiac remodelling and preserved cardiac function following myocardial infarction. The TheraCyte device can be employed to deliver stem cells in a minimally invasive manner for effective secretome-based cardiac therapy.

Reducing or increasing β-cell apoptosis without inflammation does not affect diabetes initiation in neonatal NOD mice

The presentation of islet antigens in the pancreatic LNs (PLNs) of mice is a developmentally regulated process. It has been hypothesized that, during physiological tissue remodeling, a wave of neonatal β-cell apoptosis may initiate diabetes in autoimmune-prone strains of mice. If true, increasing or decreasing physiological β-cell apoptosis in neonatal NOD mice should alter the time-course of antigen presentation in the PLNs. We used transgenic over-expression of either an anti-apoptotic protein (Bcl-2) or a toxic transgene (rat insulin promoter-Kb) in mouse β cells to reduce or increase neonatal β-cell apoptosis, respectively. Neither intervention affected the timing of antigen presentation in the PLNs or the initiation of islet infiltration. This suggests that under physiological conditions and in the absence of inflammation, neonatal β-cell apoptosis in NOD mice is not the trigger for antigen presentation in the draining LNs.

Islet beta-cells deficient in Bcl-xL develop but are abnormally sensitive to apoptotic stimuli

OBJECTIVE

Bcl-xL is an antiapoptotic member of the Bcl-2 family of proteins and a potent regulator of cell death. We investigated the importance of Bcl-xL for beta-cells by deleting the Bcl-x gene specifically in beta-cells and analyzing their survival in vivo and in culture.

RESEARCH DESIGN AND METHODS

Islets with beta-cells lacking the Bcl-x gene were assessed in vivo by histology and by treatment of mice with low-dose streptozotocin (STZ). Islets were isolated by collagenase digestion and treated in culture with the apoptosis inducers staurosporine, thapsigargin, gamma-irradiation, proinflammatory cytokines, or Fas ligand. Cell death was assessed by flow cytometric analysis of subgenomic DNA.

RESULTS

Bcl-xL-deficient beta-cells developed but were abnormally sensitive to apoptosis induced in vivo by low-dose STZ. Although a small proportion of beta-cells still expressed Bcl-xL, these did not have a survival advantage over their Bcl-xL-deficient neighbors. Islets appeared normal after collagenase isolation and whole-islet culture. They were, however, abnormally sensitive in culture to a number of different apoptotic stimuli including cytotoxic drugs, proinflammatory cytokines, and Fas ligand.

CONCLUSIONS

Bcl-xL expression in beta-cells is dispensible during islet development in the mouse. Bcl-xL is, however, an important regulator of beta-cell death under conditions of synchronous stress. Bcl-xL expression at physiological levels may partially protect beta-cells from apoptotic stimuli, including apoptosis because of mediators implicated in type 1 diabetes and death or degeneration of transplanted islets.

Temozolomide and interferon alpha 2b in metastatic melanoma stage IV

BACKGROUND

A multicentre, centrally randomized, open-labelled study with temozolomide and interferon (IFN)-alpha 2b was carried out to study the therapeutic effect in patients with metastatic melanoma stage IV.

OBJECTIVES

The response rate, efficacy, side-effects, reasons for discontinuation of therapy and survival rate of 47 patients treated with temozolomide in combination with two different dosing regimens of IFN-alpha 2b were documented.

PATIENTS/METHODS

Twenty-nine male and 18 female patients (mean age 57.6 years, range 34-74) were centrally randomized to two different arms: 20 patients received a treatment schedule with temozolomide 150 mg m(-2) on days 1-5 orally every 28 days in combination with IFN-alpha 2b 10 MIU m(-2) every other day and 27 patients received temozolomide 150 mg m(-2) on days 1-5 every 28 days in combination with IFN-alpha 2b in a fixed dose of 10 MIU every other day.

RESULTS

We observed an overall response rate of 27.6% comprising five complete remissions (10.6%: one patient group A, four patients group B), in two of these five patients at the last follow-up in the study (4.3%, both in group B); and eight partial remissions (17%: six patients in group A, two patients in group B), in three of these eight patients at the last follow-up in the study (6.4%, two patients in group A, one patient in group B). Three patients showed stable disease (6.4%: one patient in group A, two patients in group B). Mean survival was 14.5 months [95% confidence interval (CI) 10-19] with no significant differences between treatment groups. However, there was a significant correlation with response after three cycles (log rank test, P < 0.03). Within the 32 patients who completed at least three cycles of therapy, seven patients (three in group A and four in group B) with a partial or complete response showed a significantly better mean survival of 30.6 months (95% CI 19.1-42) compared with 25 patients who did not respond (13.7 months 95% CI 9.2-18.3). In total, patients with at least one complete remission showed the longest survival (37.1 months 95% CI 26.3-47.9), followed by patients with at least one partial response (17.4 95% CI 10.9-23.9). Major side-effects of the treatment were nausea, vomiting, headache, leucopenia, thrombopenia, elevation of liver function parameters and neurological symptoms. In five patients, the side-effects led to a discontinuation of treatment: neurological symptoms (two patients), sepsis (one patient), brain haemorrhage (one patient) and exanthema (one patient). There were no treatment-related deaths.

CONCLUSIONS

The combination of temozolomide and IFN-alpha 2b can easily be administered and shows tolerable toxicity. When an objective response occurs after three cycles, it indicates a significant survival advantage.

Extracellular calcium elicits a chemokinetic response from monocytes in vitro and in vivo

Recruitment of macrophages to sites of cell death is critical for induction of an immunologic response. Calcium concentrations in extracellular fluids vary markedly, and are particularly high at sites of injury or infection. We hypothesized that extracellular calcium participates in modulating the immune response, perhaps acting via the seven-transmembrane calcium-sensing receptor (CaR) on mature monocytes/macrophages. We observed a dose-dependent increase in monocyte chemotaxis in response to extracellular calcium or the selective allosteric CaR activator NPS R-467. In contrast, monocytes derived from mice deficient in CaR lacked the normal chemotactic response to a calcium gradient. Notably, CaR activation of monocytes bearing the receptor synergistically augmented the transmigration response of monocytes to the chemokine MCP-1 in association with increased cell-surface expression of its cognate receptor, CCR2. Conversely, stimulation of monocytes with MCP-1 or SDF-1alpha reciprocally increased CaR expression, suggesting a dual-enhancing interaction of Ca(2+) with chemokines in recruiting inflammatory cells. Subcutaneous administration in mice of Ca(2+), MCP-1, or (more potently) the combination of Ca(2+) and MCP-1, elicited an inflammatory infiltrate consisting of monocytes/macrophages. Thus extracellular calcium functions as an ionic chemokinetic agent capable of modulating the innate immune response in vivo and in vitro by direct and indirect actions on monocytic cells. Calcium deposition may be both consequence and cause of chronic inflammatory changes at sites of injury, infection, and atherosclerosis.

Human ciliary neurotrophic factor: localization to the proximal region of the long arm of chromosome 11 and association with CA/GT dinucleotide repeat

Ciliary neurotrophic factor (CNTF) promotes survival and differentiation of several types of sensory, motor, sympathetic, and parasympathetic neurons. We have used the polymerase chain reaction to amplify, clone, and partially sequence CNTF cDNA from human muscle. Using a rodent-human mapping panel and fluorescence in situ hybridization, we have localized a single copy of the gene for human CNTF to the proximal long arm of chromosome 11. We have also identified a polymorphic tandem CA/GT dinucleotide repeat associated with the human CNTF gene.