Nanomedicine for the prevention, treatment and imaging of atherosclerosis

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in developed countries, with an increasing prevalence due to an aging population. The pathology underpinning CVD is atherosclerosis, a chronic inflammatory state involving the arterial wall. Accumulation of low density lipoprotein (LDL) laden macrophages in the arterial wall and their subsequent transformation into foam cells lead to atherosclerotic plaque formation. Progression of atherosclerotic lesions may gradually lead to plaque related complications and clinically manifest as acute vascular syndromes including acute myocardial or cerebral ischemia. Nanotechnology offers emerging therapeutic strategies, which may have advantage overclassical treatments for atherosclerosis. In this review, we present the potential applications of nanotechnology toward prevention, identification and treatment of atherosclerosis.     

Drug-mediated targeted disruption of multiple protein activities through functional inhibition of the Hsp90 chaperone complex

Hsp90 is an evolutionarily conserved and ubiquitously expressed molecular chaperone that mainly modulates, along with a group of co-chaperones, the general platform of protein folding and prevents the nonspecific aggregation of misfolded or unfolded proteins. In the voluminous Hsp90 clientele, a large variety of important regulatory proteins can be identified, including many whose deregulation may lead to cancer initiation and progression, such as the oncogenic clients pp60(v-src), Bcr-Abl, mutated p53, ErbB2 (Her-2), Akt, Flt3, HIF-1alpha and B-Raf. Therefore, inhibition of Hsp90 function offers the prospect of simultaneously disrupting multiple signaling pathways directly implicated in the development of malignant phenotypes. During the last few years, there has been a major focus on the development of Hsp90 specific inhibitors. This started with the discovery that certain natural products could specifically disrupt Hsp90 chaperone activities. The benzoquinone ansamycin antibiotic geldanamycin and its less toxic derivative 17-AAG have been shown to possess strong anti-proliferative and apoptotic activity in cancer cells, whereas 17-AAG has demonstrated potent anti-tumor activity in several human xenograft models, including breast, prostate and colon cancer. In an effort to overcome difficulties with drug toxicity and solubility, a number of novel bioengineered 17-AAG analogues, such as 17-DMAG and IPI-504, and small-molecule inhibitors, including purine and pyrazole derivatives, have emerged from rational drug design followed by high-throughput screening approaches. 17-AAG was the leader inhibitor to enter and successfully complete phase I clinical trials, thus demonstrating that Hsp90 constitutes a valid drug target for cancer therapy. This review includes information on the current model of ternary interactions between Hsp90, client proteins and a vast array of co-chaperones followed by a list of characteristic inhibitors and ongoing clinical trials reported thus far.     

Long-term expression of murine activated factor VII is safe, but elevated levels cause premature mortality

Intravenous infusion of recombinant human activated Factor VII (FVIIa) has been used for over a decade in the successful management of bleeding episodes in patients with inhibitory antibodies to Factor VIII or Factor IX. Previously, we showed that expression of murine FVIIa (mFVIIa) from an adeno-associated viral (AAV) vector corrected abnormal hemostatic parameters in hemophilia B mice. To pursue this as a therapeutic approach, we sought to define safe and effective levels of FVIIa for continuous expression. In mice transgenic for mFVIIa or injected with AAV-mFVIIa, we analyzed survival, expression levels, in vitro and in vivo coagulation tests, and histopathology for up to 16 months after birth/mFVIIa expression. We found that continuous expression of mFVIIa at levels at or below 1.5 microg/ml was safe, effective, and compatible with a normal lifespan. However, expression levels of 2 microg/ml or higher were associated with thrombosis and early mortality, with pathologic findings in the heart and lungs that were rescued in a low-factor X (low-FX) mouse background, suggesting a FX-mediated effect. The findings from these mouse models of continuous FVIIa expression have implications for the development of a safe gene transfer approach for hemophilia and are consistent with the possibility of thromboembolic risk of continuously elevated FVIIa levels.     

Short-term memory in mice is affected by mobile phone radiation

The effects of mobile phone electromagnetic fields (EMFs) were studied on a non-spatial memory task (Object Recognition Task - ORT) that requires entorhinal cortex function. The task was applied to three groups of mice Mus musculus C57BL/6 (exposed, sham-exposed and control) combined with 3 different radiation exposure protocols. In the first protocol designated “acute exposure”, mice 45 days old (PND45 - postnatal day 45) were exposed to mobile phone (MP) radiation (SAR value 0.22 W/kg) during the habituation, the training and the test sessions of the ORT, but not during the 10 min inter-trial interval (ITI) where consolidation of stored object information takes place. On the second protocol designated “chronic exposure-I”, the same mice were exposed for 17 days for 90 min/per day starting at PND55 to the same MP radiation. ORT recognition memory was performed at PND72 with radiation present only during the ITI phase. In the third protocol designated “chronic exposure-II”, mice continued to be exposed daily under the same conditions up to PND86 having received radiation for 31 days. One day later the ORT test was performed without irradiation present in any of the sessions. The ORT-derived discrimination indices in all three exposure protocols revealed a major effect on the “chronic exposure-I” suggesting a possible severe interaction of EMF with the consolidation phase of recognition memory processes. This may imply that the primary EMF target may be the information transfer pathway connecting the entorhinal-parahippocampal regions which participate in the ORT memory task.     

Novel methods of balancing covariates for the assessment of dental erosion: a contribution to validation of a synthetic scoring system for erosive wear

Objectives

The purpose of the study was to balance several potential erosive covariates, using traditional and novel epidemiological approaches, in order to assess the relative risks of dental erosion more precisely.

Methods

Traditional (univariate and logistic regression analysis) and novel techniques (propensity scores and Inverse Probability Weighting—IPW) were applied for evaluating the effect of twenty covariates on dental erosion among 502 adolescents.

Results

Different approaches gave different estimates of the relative risks of dental erosion. The increased consumption of carbonated soft drinks had the major erosive effect, when traditional analyses were used (unadjusted: OR = 3.475 and CI: 1.499-8.052, logistic regression: OR = 3.219 and CI: 1.373-7.547). On the other hand, IPW method indicated that the consumption of erosion drinks immediately after intense physical exercise had the highest odds ratio (OR = 1.363 and CI: 0.963-1.929), followed by the increased consumption of citrus fruit juice (OR = 1.326 and CI: 1.004-1.752). This method also demonstrated a marked improvement in balance, with the 95% CIs for each OR being considerably narrower than those reported in the initial analysis.

Conclusions

Standardization of the potential aetiological criteria of erosive wear is a considerably difficult process. Nevertheless, novel methods revealed that the increased consumption of carbonated soft drinks and citrus fruit juices could be included as aetiologic factors in a synthetic scoring system for erosion. Parameters which are related to salivary protective mechanisms (e.g. consumption of erosion drinks immediately after intense physical exercise) could also be a part of such an index. Further research is required in order to achieve the maximum validation of the potential erosive risk factors.     

Over-expression of factor VIIa in vivo

Although recombinant factor VIIa has been shown to bypass the deficiency in factor VIII or factor IX, efforts to reduce factor consumption and subsequently treatment cost have been focused on continuous infusion regimens with variable success. Using an engineered factor VII that can be secreted as factor VIIa, viral-mediated delivery of this transgene in the mouse liver resulted in phenotypic correction of murine hemophilia B, at expression levels of approximately 1 microg/ml. This model of factor VIIa continuous infusion can be further used to address the potential risk of thrombosis, in a transgenic model approach. The relative contribution of the extrinsic and/or intrinsic pathways in such risk can be dissected by crossing over-expressing FVIIa mice to recently described models of low expression of tissue factor or factor X. Our current data support the potential of factor VIIa gene transfer as a therapeutic alternative to bolus dosing but effective monitoring and modulation of factor VIIa expression will most likely be required.     

Deep white matter infarction: correlation of MR imaging and histopathologic findings

Focal and confluent areas of periventricular hyperintensity have been reported on magnetic resonance (MR) images in 30% of patients over 60 years of age. In order to better understand the pathologic basis of these lesions, the authors studied 14 formalin-fixed brains with MR imaging. Multiple focal areas of hyperintensity were identified in the periventricular white matter in three of the 14 brains studied (21%). Subsequent gross and microscopic pathologic examination of both hyperintense and normal-intensity areas was performed on 87 tissue sections. The larger lesions were characterized centrally by necrosis, axonal loss, and demyelination and therefore represent true infarcts. Reactive astrocytes oriented along the degenerated axons were identified at distances of up to several centimeters from the central infarct. This is called isomorphic gliosis and is associated with increased intensity on T2-weighted images that increases the apparent size of the central lesion.