OBJECTIVE-␤-Cell proliferation is an important mechanism underlying ␤-cell mass adaptation to metabolic demands. We have examined effects, in particular those mediated through intracellular cAMP signaling, of the incretin hormone analog exendin-4 on cell cycle regulation in ␤-cells.RESEARCH DESIGN AND METHODS-Changes in islet protein levels of cyclins and of two critical cell cycle regulators cyclin kinase inhibitor p27 and S-phase kinase-associated protein 2 (Skp2) were assessed in mice treated with exendin-4 and in a mouse model with specific upregulation of nuclear cAMP signaling exhibiting increased ␤-cell proliferation (CBP-S436A mouse). Because cyclin A2 was stimulated by cAMP, we assessed the role of cylcin A2 in cell cycle progression in Min6 and isolated islet ␤-cells.RESULTS-Mice treated with exendin-4 showed increased ␤-cell proliferation, elevated islet protein levels of cyclin A2 with unchanged D-type cyclins, elevated PDX-1 and Skp2 levels, and reduced p27 levels. Exendin-4 stimulated cyclin A2 promoter activity via the cAMP-cAMP response element binding protein pathway. CBP-S436A islets exhibited elevated cyclin A2, reduced p27, and no changes in D-type cyclins, PDX-1, or Skp2. In cultured islets, exendin-4 increased cyclin A2 and Skp2 and reduced p27. Cyclin A2 overexpression in primary islets increased proliferation and reduced p27. In Min6 cells, cyclin A2 knockdown prevented exendin-4 -stimulated proliferation. PDX-1 knockdown reduced exendin-4 -stimulated cAMP synthesis and cyclin A2 transcription.CONCLUSIONS-Cyclin A2 is required for ␤-cell proliferation, exendin-4 stimulates cyclin A2 expression via the cAMP pathway, and exendin-4 stimulation of cAMP requires PDX-1. Diabetes 57:2371-2381, 2008 P ancreatic ␤-cell mass is dynamic and responds to variations in metabolic demand on insulin production. The inability of the endocrine pancreas to adapt to changing insulin demand (inadequate ␤-cell mass) is found both in type 1 and type 2 diabetes. Increasing ␤-cell mass by regeneration may ameliorate or correct both type 1 and 2 diabetes (1). Within the pancreas, ␤-cells regenerate predominantly by ␤-cell replication (2,3). In this context, insight into the mechanisms underlying ␤-cell proliferation and cell cycle regulation, may provide potential targets for therapy in situations of inadequate ␤-cell mass.The incretin hormone glucagon-like peptide-1 (GLP-1) and its long-acting peptide analog exendin-4 stimulate ␤-cell proliferation in vitro and in vivo (4), leading to increased ␤-cell mass in rodents and amelioration of glucose metabolism in diabetic animal models and human diabetic subjects (4). Downstream effectors of the GLP-1 signaling to the cell nucleus include 1) the epidermal growth factor receptor-phosphoinositol 3-kinase (PI 3-kinase)-protein kinase B (PKB/Akt)-forkhead box transcription factor O1 (FoxO1) pathway (5) and 2) the cAMP-protein kinase A (PKA)-cAMP response element binding protein (CREB) pathway (4). Activation of the PI 3-kinase pathway results in phosphorylation and nuclear...

Abstract-Neutrophil activation and increased migration is associated with preeclampsia and is resolved after delivery.Preeclampsia is an inflammatory disorder where altered levels of vascular endothelial growth factor (VEGF) and the circulating soluble fms-like tyrosine kinase 1 (sFlt-1) have a pathogenic role. VEGF, by binding to FLT-1, induces leukocytic chemotaxis. We studied expression and function of FLT-1 in maternal neutrophils during preeclampsia and normal pregnancies. Analysis of maternal neutrophils showed the relationship between FLT-1 expression and week of gestation. Preeclamptic women express lower FLT-1 and sFLT-1 in neutrophils. In contrast, serum levels of sFLT-1 in patients with preeclampsia are increased and, therefore, inhibit upregulation of FLT-1 in neutrophils by neutralizing VEGF. VEGF-dependent FLT-1 expression is regulated by changing FLT-1-promoter activity. Promoter activity is decreased by sFLT-1. In vitro experiments demonstrated that migration of neutrophils is regulated by VEGF via FLT-1 and excess of sFLT-1. Thus, VEGF-dependent migration of neutrophils is decreased during preeclampsia as a consequence of excess circulating sFlt1. But, they still increase migration by fMLP and, therefore, migration of neutrophils from preeclamptic women is highly activated when compared with the normotensive group. In conclusion, besides being involved in inducing an antiangiogenic state in the serum, excess of sFLT-1 seems to prevent activated neutrophils from women with preeclampsia from additional migration by VEGF. We provide evidence that neutrophils may be involved in the pathophysiology of pregnancy-related hypertensive disorders. Key Words: migration Ⅲ neutrophils Ⅲ preeclampsia Ⅲ pregnancy Ⅲ VEGF receptor 1 P reeclampsia (PE) is a hypertensive disorder of unknown etiology affecting 5% to 10% of all pregnancies. Pathophysological changes include elevated systemic vascular resistance, generalized vasoconstriction, activation of the coagulation cascade, maternal endothelial dysfunction, and a poorly perfused fetoplacental unit. 1 Preeclampsia is characterized by altered cytokine production 2 and marked neutrophil activation. 3-6 They release proteases and reactive oxygen species, which can cause vascular endothelial injury, inappropriate endothelial activation or transformation. 7-9 The latter processes are important for physiological adaptations during normal pregnancy creating a low-resistance arteriolar system, which allows adequate blood supply to the growing fetus. 10,11 Recently, case-control studies have shown associations between polymorphisms of the vascular endothelial growth factor (VEGF) gene and preeclampsia. 12 VEGF is a multifunctional cytokine that plays a pivotal role in angiogenesis in vivo. 13 VEGF is expressed by different cells, eg, smooth muscle, endothelial cells, monocytes/macrophages, and polymorphonuclear neutrophils (PMNs). VEGF exerts its biological effects through Fms-like tyrosine kinase 1 (FLT-1)/ VEGF receptor-1 and VEGF receptor-2 (FLK-1/KDR). 13 KDR is con...

We reported recently that 1-bromopropane (1-BP; n-propylbromide, CAS Registry no. 106-94-5), an alternative to ozone-depleting solvents, is neurotoxic and exhibits reproductive toxicity in rats. The four most recent case reports suggested possible neurotoxicity of 1-BP in workers. The aim of the present study was to establish the neurologic effects of 1-BP in workers and examine the relationship with exposure levels. We surveyed 27 female workers in a 1-BP production factory and compared 23 of them with 23 age-matched workers in a beer factory as controls. The workers were interviewed and examined by neurologic, electrophysiologic, hematologic, biochemical, neurobehavioral, and postural sway tests. 1-BP exposure levels were estimated with passive samplers. Tests with a tuning fork showed diminished vibration sensation of the foot in 15 workers exposed to 1-BP but in none of the controls. 1-BP factory workers showed significantly longer distal latency in the tibial nerve than did the controls but no significant changes in motor nerve conduction velocity. Workers also displayed lower values in sensory nerve conduction velocity in the sural nerve, backward recalled digits, Benton visual memory test scores, pursuit aiming test scores, and five items of the Profile of Mood States (POMS) test (tension, depression, anxiety, fatigue, and confusion) compared with controls matched for age and education. Workers hired after May 1999, who were exposed to 1-BP only (workers hired before 1999 could have also been exposed to 2-BP), showed similar changes in vibration sense, distal latency, Benton test scores, and depression and fatigue in the POMS test. Time-weighted average exposure levels in the workers were 0.34–49.19 ppm. Exposure to 1-BP could adversely affect peripheral nerves or/and the central nervous system.

Jintrolong® is a long-acting PEGylated recombinant human growth hormone (PEG-rhGH) developed for weekly injection in patients with pediatric growth hormone deficiency (PGHD). Although PEG modification of therapeutic proteins is generally considered safe, concerns persist about the potential for adverse vacuolation in tissues with long-term exposure to PEG-included therapies, particularly in children. We assessed the safety of Jintrolong® in cynomolgus monkeys with an examination of vacuolation in the brain choroid plexus (CP) and reported long-term clinical safety data obtained from children with PGHD. The toxicity of Jintrolong® was assessed following the 52-week administration with doses at 0.3, 1, or 3 mg/kg/week. The levels of vacuolation of CP in animals were dose-dependent and at least partially reversible after a 104- or 157-week recovery period. Vacuolation in the CP epithelium did not lead to obvious subcellular structural or cell functional abnormalities. Compared with the clinical dose of 0.2 mg/kg/week Jintrolong® in PGHD patients, exposure in monkeys under NOAEL 3 mg/kg/week exhibited safety margins greater than 120.5, the predicted minimum dose to induce vacuolation in monkeys is equivalent to 1.29 mg/kg/week in humans, which is 6.45-fold higher than the clinical dose. The safety data acquired in clinical trials for Jintrolong® were also analyzed, which included phase III (360 patients), phase IV (3,000 patients) of 26-week treatment, and a follow-up study with treatment lasting for 3 years. There was no statistically significant difference in the incidence of adverse reactions between the Jintrolong® group and the daily rhGH control group (no PEG), and no new adverse effects (AE) were observed in the Jintrolong® group at the clinical therapeutic dose of 0.2 mg/kg/week.