ATP-sensitive K ؉ (K ATP ) channels are known to play important roles in various cellular functions, but the direct consequences of disruption of K ATP channel function are largely unknown. We have generated transgenic mice expressing a dominant-negative form of the K ATP channel subunit Kir6.2 (Kir6.2G132S, substitution of glycine with serine at position 132) in pancreatic beta cells. Kir6.2G132S transgenic mice develop hypoglycemia with hyperinsulinemia in neonates and hyperglycemia with hypoinsulinemia and decreased beta cell population in adults. K ATP channel function is found to be impaired in the beta cells of transgenic mice with hyperglycemia. In addition, both resting membrane potential and basal calcium concentrations are shown to be significantly elevated in the beta cells of transgenic mice. We also found a high frequency of apoptotic beta cells before the appearance of hyperglycemia in the transgenic mice, suggesting that the K ATP channel might play a significant role in beta cell survival in addition to its role in the regulation of insulin secretion. ATP-sensitive Kϩ (K ATP ) channels are thought to regulate various cellular functions such as secretion and muscle and neural excitability by linking the cell's metabolic state to its membrane potential (1-7). We have shown previously that K ATP channels comprise at least two subunits, a sulfonylurea receptor (SUR), which belongs to the ATP-binding cassette superfamily (8), and the inward rectifier K ϩ channel member Kir6.2 (9). SUR is thought to confer the ATP and sulfonylurea sensitivities of K ATP channels, and Kir6.2 is thought to form the K ϩ ion-selective pore (9-12). However, a recent study (13)suggests that Kir6.2 alone might confer ATP-sensitivity. Although mutations of SUR1, the other subunit of pancreatic beta cell K ATP (SUR1͞Kir6.2) channels, is known to cause familial persistent hyperinsulinemic hypoglycemia of infancy (PHHI) due to a loss of functional K ATP channels (14-18), the consequences of inhibition of Kir6.2 function are unknown.The putative K ϩ ion permeable domain (H5) is highly conserved in K ϩ channels (19), and the motif Gly-Tyr (or Phe)-Gly in H5 is thought to be critical for K ϩ ion selectivity (19)(20)(21). A substitution of the first residue of the Gly-Tyr-Gly motif with serine (residue 156) is found in the G-protein-gated inward rectifier GIRK2 (Kir3.2) of weaver mice (22). This mutation is responsible for their abnormalities of neuronal differentiation and development (23)(24)(25)(26). In the present study, we have replaced the Gly-312 with Ser at the corresponding position of Kir6.2 (Kir6.2G132S) by in vitro mutagenesis. We found by 86 Rb ϩ flux measurements that Kir6.2G132S functions as a dominant-negative mutant. We then generated transgenic mice expressing Kir6.2G132S in pancreatic beta cells and studied the morphological and functional changes in the pancreatic islets.

Aminoalkyl derivatives of bisphosphonates are potent inhibitors of bone resorption. A single I.P. injection of 4-amino-1-hydroxybutylidene-1,1-bis-phosphonate (AHBuBP) induced a prolonged enhancement of histidine decarboxylase (HDC) activity in the bone marrow, spleen, lung, and liver of mice and resulted in an increase in histamine. The induction of HDC by the agent was dose dependent (16-80 mumol/kg) and peaked 3-4 days after its injection (40 mumol/kg). Repeated S.C. injections of smaller doses of AHBuBP (0.32 or 1.6 mumol/kg/day) for 4 days also enhanced HDC activity. However, the minimum dose capable of inhibiting bone resorption (0.064 mumol/kg/day) was lower than that inducing HDC. Unexpectedly, AHBuBP, at the doses inducing HDC, increased macrophages, granulocytes, and even osteoclasts. The size of osteoclasts was also enlarged by the agent. Another aminobisphosphonate, 3-amino-1-hydroxypropylidene-1,1-bisphosphonate, but none of non-amino derivatives, also exhibited essentially the same effects as those of AHBuBP. These results indicate that in spite of increase in osteoclasts and their enlargement, bone resorption is still inhibited by amino bisphosphonates. As granulocyte and granulocyte-macrophage colony-stimulating factors and interleukin-3 induce HDC in hematopoietic organs, and histamine has a hematopoietic activity, the HDC induction by aminobisphosphonates may be relevant to the proliferation of progenitor cells of macrophages, granulocytes, and osteoclasts.

No abstract

Automobile exhaust is considered to be a potential risk factor for respiratory diseases. To investigate the effects of traffic-related air pollution on respiratory symptoms among children who lived near trunk roads, we conducted a cohort study on 2,506 schoolchildren in eight different communities in Japan. Over that four-year period, the prevalence of asthma was higher among girls who lived less than 50 m from trunk roads (roadside areas) than among girls in the other areas studied. Testing for trends showed that the prevalence of asthma among girls increased significantly with increases in the concentration of air pollution in each area. Among boys, the prevalence of asthma did not differ in relation to the distance from roads, although the rate was higher in urban areas than in rural areas. The incidence of asthma during the follow-up period significantly increased among boys living in roadside areas relative to rural areas (odds ratio = 3.75; 95% confidence interval: 1.00-14.06). Among girls, the incidence of asthma also increased (odds ratio = 4.06; 95% confidence interval:0.91-18.10), although the risk was not significant. These findings suggest that traffic-related air pollution may be of particular importance in the development of asthma among children living near major trunk roads with heavy traffic.

No abstract

Our previous work has shown that injection into mice of lipopolysaccharide (LPS) and the cytokines interleukin 1 (IL‐1) and tumour necrosis factor (TNF) induces histidine decarboxylase (HDC), the enzyme forming histamine, in various tissues such as liver, lung, spleen and bone marrow, but not in the blood. The induction of HDC also occurs in nude mice and mast cell‐deficient mice. On the other hand, haematopoietic cytokines such as IL‐3, granulocyte colony‐stimulating factor (G‐CSF) and granulocyte – macrophage CSF (GM‐CSF) only induce HDC in the haematopoietic organs, i.e. bone marrow and spleen. In the present study, the effect of macrophage depletion on the induction of HDC was examined. On day 1 after a single intravenous injection of a macrophage depletor (liposomes encapsulating dichloromethylene diphosphonate, which is toxic when ingested into macrophages), macrophages were almost completely depleted in the liver and reduced by about 50% in the spleen and bone marrow, but not significantly affected in the lung. On day 3, the degrees of the depletion were similar to those of day 1. In the spleen, macrophages were depleted in the red pulp, and there was a structural destruction. In macrophage‐depleted mice, the induction of HDC by LPS, IL‐1α or TNF‐α was not impaired in the liver, and was potentiated in the lung and bone marrow. The induction of HDC was decreased only in the spleen at day 3. HDC was not induced by LPS in the spleen of the adult rat, which is correspondingly inactive in haematopoiesis. These results indicate that the major cells in which HDC activity is induced in response to LPS, IL‐1 and TNF are not circulating granulocytes, circulating monocytes, T cells derived from thymus, mast cells or phagocytic macrophages. Based on these results, we discuss the possibility that the major cells in which HDC was induced in non‐haematopoietic and haematopoietic organs were endothelial cells and haematopoietic precursor cells respectively.

No abstract

We previously demonstrated that intramuscular plasmid injection serves as a useful method of long-term systemic delivery of cytokines. In the present study, we assess intramuscular DNA injection as a means of systemically delivering interleukin 10 (IL-10), a cytokine with immunosuppressive properties, and preventing the progression of autoimmune diabetes in the nonobese diabetic (NOD) mouse, an excellent model for human insulin-dependent diabetes mellitus (IDDM). We injected IL-10 expression plasmid (pCAGGS-IL10) or a control pCAGGS plasmid into the muscles of NOD mice twice at 3 and 5 weeks of age. IL-10 was detectable by ELISA in the sera of mice injected with pCAGGS-IL10 for more than 2 weeks after the injection. Although the severity of insulitis at 13 weeks of age was not improved by the intramuscular injection of pCAGGS-IL10, the incidence of diabetes was markedly reduced in NOD mice injected with pCAGGS-IL10 as compared with those injected with pCAGGS or as compared with nontreated NOD mice. These results show that the progression of autoimmune diseases in mice can effectively be suppressed by intramuscular DNA injection, and suggest that this method is potentially applicable to the treatment of human autoimmune diseases.