Amorphous nanosilicas induce consumptive coagulopathy after systemic exposure.

We previously reported that well-dispersed amorphous nanosilicas with particle size 70 nm (nSP70) penetrate skin and produce systemic exposure after topical application. These findings underscore the need to examine biological effects after systemic exposure to nanosilicas. The present study was designed to examine the biological effects. BALB/c mice were intravenously injected with amorphous nanosilicas of sizes 70, 100, 300, 1000 nm and then assessed for survival, blood biochemistry, and coagulation. As a result, injection of nSP70 caused fatal toxicity, liver damage, and platelet depletion, suggesting that nSP70 caused consumptive coagulopathy. Additionally, nSP70 exerts procoagulant activity in vitro associated with an increase in specific surface area, which increases as diameter reduces. In contrast, nSP70-mediated procoagulant activity was absent in factor XII-deficient plasma. Collectively, we revealed that interaction between nSP70 and intrinsic coagulation factors such as factor XII, were deeply related to nSP70-induced harmful effects. In other words, it is suggested that if interaction between nSP70 and coagulation factors can be suppressed, nSP70-induced harmful effects may be avoided. These results would provide useful information for ensuring the safety of nanomaterials (NMs) and open new frontiers in biological fields by the use of NMs.

Compensatory recovery of blood glucose levels in KKA(y) mice fed a high-fat diet: insulin-sparing effects of PACAP overexpression in ß cells.

Inadequate compensatory insulin secretion is observed during the development of type 2 diabetes and deteriorates over time in a manner that is difficult to reverse. Here, we found that plasma glucose levels in genetically diabetic KKA(y) mice fed a high-fat diet were markedly increased in young mice. However, the levels started to decrease at 22 weeks of age and returned to normal levels at around 40 weeks of age. These changes were accompanied by a marked increase in insulin levels from week 25 onwards. Decreased energy intake and suppressed fat pad accumulation were observed at 44-45 weeks of age compared with those at 19-22 weeks of age. ß cell-specific overexpression of pituitary adenylate cyclase-activating polypeptide (PACAP), an insulinotropic neuropeptide, decreased the insulin levels required to compensate for hyperglycemia. Glucose disposal was significantly enhanced despite impaired insulin sensitivity in 41-44-week-old A(y) mice without or with PACAP overexpression. In conclusion, the present results provide further evidence that PACAP is involved in the regulation of hyperinsulinemia and islet hyperplasia in type 2 diabetes. Our results also indicate that A(y) mice fed a high-fat diet constitute an animal model suitable to study compensatory islet hyperplasia.

Cerulein-induced acute pancreatitis in PACAP knockout mice.

In our previous study, we reported that cerulein-induced acute pancreatitis is aggravated in pancreatic ß-cell-specific pituitary adenylate cyclase-activating polypeptide (PACAP) transgenic mice, showing that an increase in pancreatic PACAP is a risk factor for progression of acute pancreatitis. Accordingly, in this study, we examined the progression of cerulein-induced acute pancreatitis in PACAP knockout (KO) mice. Unexpectedly, after cerulein, about 60% of the KO mice showed severe hypothermia below 30°C by 12 h and most of them died within 72 h. In contrast, the remaining KO and wild-type mice showed normothermia with no mortality. Thus, KO mice could be classified into two groups as hypothermic (HT-KO) and normothermic (NT-KO) to cerulein. Only HT-KO mice subsequently showed severe mortality, although both HT-KO and NT-KO mice exhibited similar susceptibility of lungs to cerulein toxicity, comparable to that in wild-type mice. Regarding pancreatitis, HT-KO mice showed ameliorated pancreatic damage without any rise in serum enzyme activities, whereas NT-KO mice exhibited a similar degree of pancreatitis to wild-type mice. Taken together, the present results indicate that lack of pancreatic PACAP did not aggravate, but rather ameliorated, cerulein-induced pancreatitis. In addition, about half of KO mice showed a novel phenotype in which cerulein caused rapid and severe hypothermia, followed by death.

Effect of surface properties of silica nanoparticles on their cytotoxicity and cellular distribution in murine macrophages.

Surface properties are often hypothesized to be important factors in the development of safer forms of nanomaterials (NMs). However, the results obtained from studying the cellular responses to NMs are often contradictory. Hence, the aim of this study was to investigate the relationship between the surface properties of silica nanoparticles and their cytotoxicity against a murine macrophage cell line (RAW264.7). The surface of the silica nanoparticles was either unmodified (nSP70) or modified with amine (nSP70-N) or carboxyl groups (nSP70-C). First, the properties of the silica nanoparticles were characterized. RAW264.7 cells were then exposed to nSP70, nSP70-N, or nSP70-C, and any cytotoxic effects were monitored by analyzing DNA synthesis. The results of this study show that nSP70-N and nSP70-C have a smaller effect on DNA synthesis activity by comparison to unmodified nSP70. Analysis of the intracellular localization of the silica nanoparticles revealed that nSP70 had penetrated into the nucleus, whereas nSP70-N and nSP70-C showed no nuclear localization. These results suggest that intracellular localization is a critical factor underlying the cytotoxicity of these silica nanoparticles. Thus, the surface properties of silica nanoparticles play an important role in determining their safety. Our results suggest that optimization of the surface characteristics of silica nanoparticles will contribute to the development of safer forms of NMs.

Systemic distribution, nuclear entry and cytotoxicity of amorphous nanosilica following topical application.

Currently, nanomaterials (NMs) with particle sizes below 100 nm have been successfully employed in various industrial applications in medicine, cosmetics and foods. On the other hand, NMs can also be problematic in terms of eliciting a toxicological effect by their small size. However, biological and/or cellular responses to NMs are often inconsistent and even contradictory. In addition, relationships among NMs physicochemical properties, absorbency, localization and biological responses are not yet well understood. In order to open new frontiers in medical, cosmetics and foods fields by the safer NMs, it is necessary to collect the information of the detailed properties of NMs and then, build the prediction system of NMs safety. The present study was designed to examine the skin penetration, cellular localization, and cytotoxic effects of the well-dispersed amorphous silica particles of diameters ranging from 70 nm to 1000 nm. Our results suggested that the well-dispersed amorphous nanosilica of particle size 70 nm (nSP70) penetrated the skin barrier and caused systemic exposure in mouse, and induced mutagenic activity in vitro. Our information indicated that further studies of relation between physicochemical properties and biological responses are needed for the development and the safer form of NMs.