Microglia, the main immunocompetent cells of the brain, regulate neuronal function, but their contribution to cerebral blood flow (CBF) regulation has remained elusive. Here, we identify microglia as important modulators of CBF both under physiological conditions and during hypoperfusion. Microglia establish direct, dynamic purinergic contacts with cells in the neurovascular unit that shape CBF in both mice and humans. Surprisingly, the absence of microglia or blockade of microglial P2Y12 receptor (P2Y12R) substantially impairs neurovascular coupling in mice, which is reiterated by chemogenetically induced microglial dysfunction associated with impaired ATP sensitivity. Hypercapnia induces rapid microglial calcium changes, P2Y12R-mediated formation of perivascular phylopodia, and microglial adenosine production, while depletion of microglia reduces brain pH and impairs hypercapnia-induced vasodilation. Microglial actions modulate vascular cyclic GMP levels but are partially independent of nitric oxide. Finally, microglial dysfunction markedly impairs P2Y12R-mediated cerebrovascular adaptation to common carotid artery occlusion resulting in hypoperfusion. Thus, our data reveal a previously unrecognized role for microglia in CBF regulation, with broad implications for common neurological diseases.

The purpose of this study was to determine the absorption, distribution and excretion of ^99mtechnetium-labeled, high-molecular-weight hyaluronan ((^99mTc-HA) and ^99mtechnetium pertechnetate (^99mTc-P) after single dose, oral administration to Wistar rats and Beagle dogs. A pilot study utilized ^99mTc-HA alone, and a second confirmatory study compared uptake of labeled ^99mTc-HA with ^99mTc-P. Urinary and fecal excretion after ^99mTc-HA ingestion by rats showed 86.7−95.6% of radioactivity was recovered, almost all in feces. All tissues examined showed incorporation of radioactivity from ^99mTc-HA starting at 15 min and persisting for 48 h, in a pattern significantly different from ^99mTc-P. Whole-body scintigraphs and close-ups of the ventral chest region showed nonalimentary radioactivity from ^99mTc-HA concentrated in joints, vertebrae and salivary glands four hours after administration. Autoradiography of skin, bone and joint tissue pieces after 24 h showed incorporation of radioactivity from ^99mTc-HA, but not from ^99mTc-P. Conversely, absorption, distribution and excretion of ^99mTc was completely different from ^99mTc-HA, showing an expected pattern of rapid absorption and excretion in urine, with accumulation in thyroid glands, stomach, kidney and bladder. This report presents the first evidence for uptake and distribution to connective tissues of orally administered, high-molecular-weight HA.

The biodistribution of extracellular vesicles (EVs) is a fundamental question in the field of circulating biomarkers, which has recently gained attention. Despite the capabilities of nuclear imaging methods, such as single-photon emission computed tomography, radioisotope labeling of EVs and the use of the aforementioned methods for in vivo studies hardly can be found in the literature. In this article, the authors describe a novel method for the radioisotope labeling of erythrocyte-derived EVs using the ^99mTc-tricarbonyl complex. Moreover, the capability of the developed labeling method for in vivo biodistribution studies is demonstrated in a mouse model. The authors found that the intravenously administered ^99mTc-labeled EVs mostly accumulated in the liver and spleen. The in vivo stability of the labeled EVs was assessed by the comparison of the obtained biodistribution of EVs with that of the free ^99mTc-tricarbonyl. According to the authors' data, only a minor fraction of the radioactive label became detached from the EVs.

Magnetic nanoparticles (NPs) MnFe2O4 and Fe3O4 were stabilised by depositing an Al(OH)3 layer via a hydrolysis process. The particles displayed excellent colloidal stability in water and a high affinity to [(18)F]-fluoride and bisphosphonate groups. A high radiolabeling efficiency, 97% for (18)F-fluoride and 100% for (64)Cu-bisphosphonate conjugate, was achieved by simply incubating NPs with radioactivity solution at room temperature for 5 min. The properties of particles were strongly dependant on the thickness and hardness of the Al(OH)3 layer which could in turn be controlled by the hydrolysis method. The application of these Al(OH)3 coated magnetic NPs in molecular imaging has been further explored. The results demonstrated that these NPs are potential candidates as dual modal probes for MR and PET. In vivo PET imaging showed a slow release of (18)F from NPs, but no sign of efflux of (64)Cu.

Although incidence and prevalence of prediabetes are increasing, little is known about its cardiac effects. Therefore, our aim was to investigate the effect of prediabetes on cardiac function and to characterize parameters and pathways associated with deteriorated cardiac performance. Long-Evans rats were fed with either control or high-fat chow for 21 wk and treated with a single low dose (20 mg/kg) of streptozotocin at week 4. High-fat and streptozotocin treatment induced prediabetes as characterized by slightly elevated fasting blood glucose, impaired glucose and insulin tolerance, increased visceral adipose tissue and plasma leptin levels, as well as sensory neuropathy. In prediabetic animals, a mild diastolic dysfunction was observed, the number of myocardial lipid droplets increased, and left ventricular mass and wall thickness were elevated; however, no molecular sign of fibrosis or cardiac hypertrophy was shown. In prediabetes, production of reactive oxygen species was elevated in subsarcolemmal mitochondria. Expression of mitofusin-2 was increased, while the phosphorylation of phospholamban and expression of Bcl-2/adenovirus E1B 19-kDa protein-interacting protein 3 (BNIP3, a marker of mitophagy) decreased. However, expression of other markers of cardiac auto- and mitophagy, mitochondrial dynamics, inflammation, heat shock proteins, Ca²⁺/calmodulin-dependent protein kinase II, mammalian target of rapamycin, or apoptotic pathways were unchanged in prediabetes. This is the first comprehensive analysis of cardiac effects of prediabetes indicating that mild diastolic dysfunction and cardiac hypertrophy are multifactorial phenomena that are associated with early changes in mitophagy, cardiac lipid accumulation, and elevated oxidative stress and that prediabetes-induced oxidative stress originates from the subsarcolemmal mitochondria. Listen to this article's corresponding podcast http://ajpheart.podbean.com/e/myocardial-dysfunction-in-prediabetes/ .