Serum Corticosterone and Insulin Resistance as Early Biomarkers in the hAPP23 Overexpressing Mouse Model of Alzheimer's Disease

Increasing epidemiological evidence highlights the association between systemic insulin resistance and Alzheimer’s disease (AD). As insulin resistance can be caused by high-stress hormone levels and since hypercortisolism appears to be an important risk factor of AD, we aimed to investigate the systemic insulin functionality and circulating stress hormone levels in a mutant humanized amyloid precursor protein (APP) overexpressing (hAPP23+/−) AD mouse model. Memory and spatial learning of male hAPP23+/− and C57BL/6 (wild type, WT) mice were assessed by a Morris Water Maze (MWM) test at the age of 4 and 12 months. The systemic metabolism was examined by intraperitoneal glucose and insulin tolerance tests (GTT, ITT). Insulin and corticosterone levels were determined in serum. In the hippocampus, parietal and occipital cortex of hAPP23+/− brains, amyloid-beta (Aβ) deposits were present at 12 months of age. MWM demonstrated a cognitive decline in hAPP23+/− mice at 12 but not at 4 months, evidenced by increasing total path lengths and deteriorating probe trials compared to WT mice. hAPP23+/− animals presented increased serum corticosterone levels compared to WT mice at both 4 and 12 months. hAPP23+/− mice exhibited peripheral insulin resistance compared to WT mice at 4 months, which stabilized at 12 months of age. Serum insulin levels were similar between genotypes at 4 months of age but were significantly higher in hAPP23+/− mice at 12 months of age. Peripheral glucose homeostasis remained unchanged. These results indicate that peripheral insulin resistance combined with elevated circulating stress hormone levels could be potential biomarkers of the pre-symptomatic phase of AD

Knockout mice reveal a role for P2Y6 receptor in macrophages, endothelial cells, and vascular smooth muscle cells.

P2Y receptors are G-protein-coupled receptors activated by extracellular nucleotides. The P2Y(6) receptor is selectively activated by UDP, and its transcript has been detected in numerous organs, including the spleen, thymus, intestine, blood leukocytes, and aorta. To investigate the biological functions of this receptor, we generated P2Y(6)-null mice by gene targeting. The P2Y(6) knockout (KO) mice are viable and are not distinguishable from the wild-type (WT) mice in terms of growth or fertility. In thioglycollate-elicited macrophages, the production of inositol phosphate in response to UDP stimulation was lost, indicating that P2Y(6) is the unique UDP-responsive receptor expressed by mouse macrophages. Furthermore, the amount of interleukin-6 and macrophage-inflammatory protein-2, but not tumor necrosis factor-alpha, released in response to lipopolysaccharide stimulation was significantly enhanced in the presence of UDP, and this effect was lost in the P2Y(6) KO macrophages. The endothelium-dependent relaxation of the aorta by UDP was abolished in KO P2Y(6) mice. The contractile effect of UDP on the aorta, observed when endothelial nitric-oxide synthase is blocked, was also abolished in P2Y(6)-null mice. In conclusion, we generated P2Y(6)-deficient mice and have shown that these mice have a defective response to UDP in macrophages, endothelial cells, and vascular smooth muscle cells. These observations might be relevant to several physiopathological conditions such as atherosclerosis or hypertension.Comparative StudyJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Neuregulin-1 attenuates stress-induced vascular senescence.

Cardiovascular ageing is a key determinant of life expectancy. Cellular senescence, a state of irreversible cell cycle arrest, is an important contributor to ageing due to the accumulation of damaged cells. Targeting cellular senescence could prevent age-related cardiovascular diseases. In this study, we investigated the effects of neuregulin-1 (NRG-1), an epidermal growth factor with cardioprotective and anti-atherosclerotic effects, on cellular senescence.info:eu-repo/semantics/publishe

Endothelium-dependent relaxation evoked by ATP and UTP in the aorta of P2Y(2)-deficient mice

1. Based on pharmacological criteria, we previously suggested that in the mouse aorta, endothelium-dependent relaxation by nucleotides is mediated by P2Y(1) (adenosine diphosphate (ADP)), P2Y(2) (adenosine triphosphate (ATP)) and P2Y(6) (uridine diphosphate (UDP)) receptors. For UTP, it was unclear whether P2Y(2), P2Y(6) or yet another subtype was involved. Therefore, in view of the lack of selective purinergic agonists and antagonists, we used P2Y(2)-deficient mice to clarify the action of UTP. 2. Thoracic aorta segments (width 2 mm) of P2Y(2)-deficient and wild-type (WT) mice were mounted in organ baths to measure isometric force development and intracellular calcium signalling. 3. Relaxations evoked by ADP, UDP and acetylcholine were identical in knockout and WT mice, indicating that the receptors for these agonists function normally. 4. P2Y(2)-deficient mice showed impaired ATP- and adenosine 5′[γ-thio] triphosphate (ATPγS)-evoked relaxation, suggesting that in WT mice, ATP and ATPγS activate predominantly the P2Y(2) subtype. 5. The ATP/ATPγS-evoked relaxation and calcium signals in the knockout mice were partially rescued by P2Y(1), as they were sensitive to 2′-deoxy-N(6)-methyladenosine 3′,5′-bisphosphate (MRS2179), a P2Y(1)-selective antagonist. 6. In contrast to ATP, the UTP-evoked relaxation was not different between knockout and WT mice. Moreover, the action of UTP was not sensitive to MRS2179. Therefore, the action of UTP is probably mediated mainly by a P2Y(6)(like) receptor subtype. 7. In conclusion, we demonstrated that ATP-evoked relaxation of the murine aorta is mainly mediated by P2Y(2). But this P2Y(2) receptor has apparently no major role in UTP-evoked relaxation. The vasodilator effect of UTP is probably mediated mainly by a P2Y(6)(like) receptor

Pharmacological characterization of nucleotide P2Y receptors on endothelial cells of the mouse aorta

1. Nucleotides regulate various effects including vascular tone. This study was aimed to characterize P2Y receptors on endothelial cells of the aorta of C57BL6 mice. Five adjacent segments (width 2 mm) of the thoracic aorta were mounted in organ baths to measure isometric force development. 2. Nucleotides evoked complete (adenosine 5′ triphosphate (ATP), uridine 5′ triphosphate (UTP), uridine 5′ diphosphate (UDP); >90%) or partial (adenosine 5′ diphosphate (ADP)) relaxation of phenylephrine precontracted thoracic aortic rings of C57BL6 mice. Relaxation was abolished by removal of the endothelium and was strongly suppressed (>90%) by inhibitors of nitric oxide synthesis. 3. The rank order of potency was: UDP∼UTP∼ADP>adenosine 5′-[γ-thio] triphosphate (ATPγS)>ATP, with respective pD(2) values of 6.31, 6.24, 6.22, 5.82 and 5.40. These results are compatible with the presence of P2Y(1) (ADP>ATP), P2Y(2) or P2Y(4) (ATP and UTP) and P2Y(6) (UDP) receptors. 4. P2Y(4) receptors were not involved, since P2Y(4)-deficient mice displayed unaltered responses to ATP and UTP. 5. The purinergic receptor antagonist suramin exerted surmountable antagonism for all agonists. Its apparent pK(b) for ATP (4.53±0.07) was compatible with literature, but the pK(b) for UTP (5.19±0.03) was significantly higher. This discrepancy suggests that UTP activates supplementary non-P2Y(2) receptor subtype(s). 6. Further, pyridoxal-phosphate-6-azophenyl-2′-4′-disulphonic acid (PPADS) showed surmountable (UTP, UDP), nonsurmountable (ADP) or no antagonism (ATP). 7. Finally, 2′-deoxy-N(6)-methyladenosine3′,5′-bisphosphate (MRS2179) inhibited ADP-evoked relaxation only. 8. Taken together, these results point to the presence of functional P2Y(1) (ADP), P2Y(2) (ATP, UTP) and P2Y(6) (UDP) receptors on murine aorta endothelial cells. The identity of the receptor(s) mediating the action of UTP is not fully clear and other P2Y subtypes might be involved in UTP-evoked vasodilatation