Role of the Mitochondria in Immune-Mediated Apoptotic Death of the Human Pancreatic β Cell Line βLox5

Mitochondria are indispensable in the life and death of many types of eukaryotic cells. In pancreatic beta cells, mitochondria play an essential role in the secretion of insulin, a hormone that regulates blood glucose levels. Unregulated blood glucose is a hallmark symptom of diabetes. The onset of Type 1 diabetes is preceded by autoimmune-mediated destruction of beta cells. However, the exact role of mitochondria has not been assessed in beta cell death. In this study, we examine the role of mitochondria in both Fas- and proinflammatory cytokine-mediated destruction of the human beta cell line, βLox5. IFNγ primed βLox5 cells for apoptosis by elevating cell surface Fas. Consequently, βLox5 cells were killed by caspase-dependent apoptosis by agonistic activation of Fas, but only after priming with IFNγ. This beta cell line undergoes both apoptotic and necrotic cell death after incubation with the combination of the proinflammatory cytokines IFNγ and TNFα. Additionally, both caspase-dependent and -independent mechanisms that require proper mitochondrial function are involved. Mitochondrial contributions to βLox5 cell death were analyzed using mitochondrial DNA (mtDNA) depleted βLox5 cells, or βLox5 ρ0 cells. βLox5 ρ0 cells are not sensitive to IFNγ and TNFα killing, indicating a direct role for the mitochondria in cytokine-induced cell death of the parental cell line. However, βLox5 ρ0 cells are susceptible to Fas killing, implicating caspase-dependent extrinsic apoptotic death is the mechanism by which these human beta cells die after Fas ligation. These data support the hypothesis that immune mediators kill βLox5 cells by both mitochondrial-dependent intrinsic and caspase-dependent extrinsic pathways

Hymyc1 Downregulation Promotes Stem Cell Proliferation in Hydra vulgaris

Hydra is a unique model for studying the mechanisms underlying stem cell biology. The activity of the three stem cell lineages structuring its body constantly replenishes mature cells lost due to normal tissue turnover. By a poorly understood mechanism, stem cells are maintained through self-renewal while concomitantly producing differentiated progeny. In vertebrates, one of many genes that participate in regulating stem cell homeostasis is the protooncogene c-myc, which has been recently identified also in Hydra, and found expressed in the interstitial stem cell lineage. In the present paper, by developing a novel strategy of RNA interference-mediated gene silencing (RNAi) based on an enhanced uptake of small interfering RNAi (siRNA), we provide molecular and biological evidence for an unexpected function of the Hydra myc gene (Hymyc1) in the homeostasis of the interstitial stem cell lineage. We found that Hymyc1 inhibition impairs the balance between stem cell self renewal/differentiation, as shown by the accumulation of stem cell intermediate and terminal differentiation products in genetically interfered animals. The identical phenotype induced by the 10058-F4 inhibitor, a disruptor of c-Myc/Max dimerization, demonstrates the specificity of the RNAi approach. We show the kinetic and the reversible feature of Hymyc1 RNAi, together with the effects displayed on regenerating animals. Our results show the involvement of Hymyc1 in the control of interstitial stem cell dynamics, provide new clues to decipher the molecular control of the cell and tissue plasticity in Hydra, and also provide further insights into the complex myc network in higher organisms. The ability of Hydra cells to uptake double stranded RNA and to trigger a RNAi response lays the foundations of a comprehensive analysis of the RNAi response in Hydra allowing us to track back in the evolution and the origin of this process

RNA interference-mediated c-MYC inhibition prevents cell growth and decreases sensitivity to radio- and chemotherapy in childhood medulloblastoma cells

BACKGROUND: With current treatment strategies, nearly half of all medulloblastoma (MB) patients die from progressive tumors. Accordingly, the identification of novel therapeutic strategies remains a major goal. Deregulation of c-MYC is evident in numerous human cancers. In MB, over-expression of c-MYC has been shown to cause anaplasia and correlate with unfavorable prognosis. METHODS: To study the role of c-MYC in MB biology, we down-regulated c-MYC expression by using small interfering RNA (siRNA) and investigated changes in cellular proliferation, cell cycle analysis, apoptosis, telomere maintenance, and response to ionizing radiation (IR) and chemotherapeutics in a representative panel of human MB cell lines expressing different levels of c-MYC (DAOY wild-type, DAOY transfected with the empty vector, DAOY transfected with c-MYC, D341, and D425). RESULTS: siRNA-mediated c-MYC down-regulation resulted in an inhibition of cellular proliferation and clonogenic growth, inhibition of G1-S phase cell cycle progression, and a decrease in human telomerase reverse transcriptase (hTERT) expression and telomerase activity. On the other hand, down-regulation of c-MYC reduced apoptosis and decreased the sensitivity of human MB cells to IR, cisplatin, and etoposide. This effect was more pronounced in DAOY cells expressing high levels of c-MYC when compared with DAOY wild-type or DAOY cells transfected with the empty vector. CONCLUSION: In human MB cells, in addition to its roles in growth and proliferation, c-MYC is also a potent inducer of apoptosis. Therefore, targeting c-MYC might be of therapeutic benefit when used sequentially with chemo- and radiotherapy rather than concomitantly

A role for activin A and betacellulin in human fetal pancreatic cell differentiation and growth

Activin A (Act.A), a member of the transforming growth factor beta family of secreted proteins, has been implicated in the regulation of growth and differentiation of various cell types. Betacellulin (BTC), a member of the epidermal growth factor family, converts exocrine AR42J cells to insulin-expressing cells when combined with Act.A. We have used primary cultures of human fetal pancreatic tissue to identify the effects of Act.A and/or ETC on islet development and growth. Exposure to Act.A resulted in a 1.5-fold increase in insulin content (P < 0.005) and a 2-fold increase in the number of cells immunopositive for insulin (P < 0.005). the formation of islet-like cell clusters, containing mainly epithelial cells, during a Ei-day culture, was stimulated 1.4-fold by ETC (P < 0.05). ETC alone caused a 2.6-fold increase in DNA synthesis (P < 0.005). These data suggest that Act.A induces endocrine differentiation, whereas BTC has a mitogenic effect on human undifferentiated pancreatic epithelial cells.Univ Calif San Diego, Dept Pediat, Islet Res Lab, La Jolla, CA 92037 USAUniv Calif San Diego, Whittier Inst, La Jolla, CA 92037 USAUniversidade Federal de São Paulo, São Paulo, BrazilUniversidade Federal de São Paulo, São Paulo, BrazilWeb of Scienc

Trends in Type 1 Diabetic Ketoacidosis During COVID-19 Surges at 7 US Centers: Highest Burden on non-Hispanic Black Patients

Abstract Context The impact of the COVID-19 pandemic on individuals with type 1 diabetes remains poorly defined. Objective We examined United States trends in diabetic ketoacidosis (DKA) among individuals with type 1 diabetes (T1D) during the COVID-19 pandemic at 7 large US medical centers and factors associated with these trends. Methods We compared DKA events among children and adults with T1D during COVID-19 surge 1 (March-May 2020) and COVID-19 surge 2 (August-October 2020) to the same periods in 2019. Analysis was performed using descriptive statistics and chi-square tests. Results We found no difference in the absolute number of T1D patients experiencing DKA in 2019 vs 2020. However, a higher proportion of non-Hispanic Black (NHB) individuals experienced DKA in 2019 than non-Hispanic White (NHW) individuals (44.6% vs 16.0%; P &amp;lt; .001), and this disparity persisted during the COVID-19 pandemic (48.6% vs 18.6%; P &amp;lt; .001). DKA was less common among patients on continuous glucose monitor (CGM) or insulin pump in 2020 compared to 2019 (CGM: 13.2% vs 15.0%, P &amp;lt; .001; insulin pump: 8.0% vs 10.6%, P &amp;lt; .001). In contrast to annual DKA totals, a higher proportion of patients had DKA during COVID-19 surges 1 and 2 compared to the same months in 2019 (surge 1: 7.1% vs 5.4%, P &amp;lt; .001; surge 2: 6.6% vs 5.7%, P = .001). Conclusion DKA frequency increased among T1D patients during COVID-19 surges with highest frequency among NHB patients. DKA was less common among patients using CGM or insulin pumps. These findings highlight the urgent need for improved strategies to prevent DKA among patients with T1D—not only under pandemic conditions, but under all conditions—especially among populations most affected by health inequities. </jats:sec