Early postnatal lead exposure induces tau phosphorylation in the brain of young rats

Cognitive impairment is a common feature of both lead exposure and hyperphosphorylation of tau. We, therefore, investigated whether lead exposure would induce tau hyperphosphorylation. Wistar rat pups were exposed to 0.2% lead acetate via their dams’ drinking water from postnatal day 1 to 21. Lead in blood and brain were measured by atomic absorption spectrophotometry and the expression of tau, phosphorylated tau and various serine/threonine protein phosphatases (PP1, PP2A, PP2B and PP5) in the brain was analyzed by Western blot. Lead exposure significantly impaired learning and resulted in a significant reduction in the expression of tau but increased the phosphorylation of tau at Ser199/202, Thr212/Ser214 and Thr231. PP2A expression decreased, whereas, PP1 and PP5 expression increased in lead-exposed rats. These results demonstrate that early postnatal exposure to lead decrease PP2A expression and induce tau hyperphosphorylation at several serine and threonine residues. Hyperphosphorylation of tau may be a mechanism of Pb-induced deficits in learning and memory

Cationic Polyamidoamine Dendrimers As Modulators Of Egfr Signaling In Vitro And In Vivo

Cationic polyamidoamine (PAMAM) dendrimers are branch-like spherical polymers being investigated for a variety of applications in nanomedicine including nucleic acid drug delivery. Emerging evidence suggests they exhibit intrinsic biological and toxicological effects but little is known of their interactions with signal transduction pathways. We previously showed that the activated (fragmented) generation (G) 6 PAMAM dendrimer, Superfect (SF), stimulated epidermal growth factor receptor (EGFR) tyrosine kinase signaling - an important signaling cascade that regulates cell growth, survival and apoptosis-in cultured human embryonic kidney (HEK 293) cells. Here, we firstly studied the in vitro effects of Polyfect (PF), a non-activated (intact) G6 PAMAM dendrimer, on EGFR tyrosine kinase signaling via extracellular-regulated kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) in cultured HEK 293 cells and then compared the in vivo effects of a single administration (10mg/kg i.p) of PF or SF on EGFR signaling in the kidneys of normal and diabetic male Wistar rats. Polyfect exhibited a dose- and time-dependent inhibition of EGFR, ERK1/2 and p38 MAPK phosphorylation in HEK-293 cells similar to AG1478, a selective EGFR inhibitor. Administration of dendrimers to non-diabetic or diabetic animals for 24h showed that PF inhibited whereas SF stimulated EGFR phosphorylation in the kidneys of both sets of animals. PF-mediated inhibition of EGFR phosphorylation as well as SF or PF-mediated apoptosis in HEK 293 cells could be significantly reversed by co-treatment with antioxidants such as tempol implying that both these effects involved an oxidative stress-dependent mechanism. These results show for the first time that SF and PF PAMAM dendrimers can differentially modulate the important EGFR signal transduction pathway in vivo and may represent a novel class of EGFR modulators. These findings could have important clinical implications for the use of PAMAM dendrimers in nanomedicine

Gender differences among patients with acute coronary syndrome in the Middle East

Background: There is controversy regarding the relationship between gender and acute coronary syndrome (ACS). Objective: To study the impact of gender on presentation, management, and mortality among patients with ACS in the Middle East. Methodology: From January 2012 to January 2013, 4057 patients with ACS were enrolled from four Arabian Gulf countries (Kuwait, Oman, United Arab Emirates, and Qatar), representing more than 85% of the general hospitals in each of the participating countries. Results: Compared to men, women were older and had more comorbidities. They also had atypical presentation of ACS such as atypical chest pain and heart failure. The prevalence of non-ST-segment elevation myocardial infarction (49 vs. 46%; P < 0.001) and unstable angina (34 vs. 24%; P < 0.001) was higher among women as compared to men. In addition, women were less likely to receive evidence-based medications such as aspirin, clopidogrel, beta-blocker, and angiotensin-converting enzyme inhibitors on admission and on discharge. During hospital stay, women suffered more heart failure (15 vs. 12%; P = 0.008) and were more likely to receive blood transfusion (6 vs. 3%; P < 0.001). Women had higher 1-year mortality (14 vs. 11%; P < 0.001), the apparent difference that disappeared after adjusting for age and other comorbidities. Conclusion: Although there were differences between men and women in presentation, management, and in-hospital outcomes, gender was shown to be a nonsignificant contributor to mortality after adjusting for confounders

Transactivation of ErbB Family of Receptor Tyrosine Kinases Is Inhibited by Angiotensin-(1-7) via Its Mas Receptor.

Transactivation of the epidermal growth factor receptor (EGFR or ErbB) family members, namely EGFR and ErbB2, appears important in the development of diabetes-induced vascular dysfunction. Angiotensin-(1-7) [Ang-(1-7)] can prevent the development of hyperglycemia-induced vascular complications partly through inhibiting EGFR transactivation. Here, we investigated whether Ang-(1-7) can inhibit transactivation of ErbB2 as well as other ErbB receptors in vivo and in vitro. Streptozotocin-induced diabetic rats were chronically treated with Ang-(1-7) or AG825, a selective ErbB2 inhibitor, for 4 weeks and mechanistic studies performed in the isolated mesenteric vasculature bed as well as in cultured vascular smooth muscle cells (VSMCs). Ang-(1-7) or AG825 treatment inhibited diabetes-induced phosphorylation of ErbB2 receptor at tyrosine residues Y1221/22, Y1248, Y877, as well as downstream signaling via ERK1/2, p38 MAPK, ROCK, eNOS and IkB-α in the mesenteric vascular bed. In VSMCs cultured in high glucose (25 mM), Ang-(1-7) inhibited src-dependent ErbB2 transactivation that was opposed by the selective Mas receptor antagonist, D-Pro7-Ang-(1-7). Ang-(1-7) via Mas receptor also inhibited both Angiotensin II- and noradrenaline/norephinephrine-induced transactivation of ErbB2 and/or EGFR receptors. Further, hyperglycemia-induced transactivation of ErbB3 and ErbB4 receptors could be attenuated by Ang-(1-7) that could be prevented by D-Pro7-Ang-(1-7) in VSMC. These data suggest that Ang-(1-7) via its Mas receptor acts as a pan-ErbB inhibitor and might represent a novel general mechanism by which Ang-(1-7) exerts its beneficial effects in many disease states including diabetes-induced vascular complications

Activation of ErbB2 and Downstream Signalling via Rho Kinases and ERK1/2 Contributes to Diabetes-Induced Vascular Dysfunction.

Diabetes mellitus leads to vascular complications but the underlying signalling mechanisms are not fully understood. Here, we examined the role of ErbB2 (HER2/Neu), a transmembrane receptor tyrosine kinase of the ErbB/EGFR (epidermal growth factor receptor) family, in mediating diabetes-induced vascular dysfunction in an experimental model of type 1 diabetes. Chronic treatment of streptozotocin-induced diabetic rats (1 mg/kg/alt diem) or acute, ex-vivo (10(-6), 10(-5) M) administration of AG825, a specific inhibitor of ErbB2, significantly corrected the diabetes-induced hyper-reactivity of the perfused mesenteric vascular bed (MVB) to the vasoconstrictor, norephinephrine (NE) and the attenuated responsiveness to the vasodilator, carbachol. Diabetes led to enhanced phosphorylation of ErbB2 at multiple tyrosine (Y) residues (Y1221/1222, Y1248 and Y877) in the MVB that could be attenuated by chronic AG825 treatment. Diabetes- or high glucose-mediated upregulation of ErbB2 phosphorylation was coupled with activation of Rho kinases (ROCKs) and ERK1/2 in MVB and in cultured vascular smooth muscle cells (VSMC) that were attenuated upon treatment with either chronic or acute AG825 or with anti-ErbB2 siRNA. ErbB2 likley heterodimerizes with EGFR, as evidenced by increased co-association in diabetic MVB, and further supported by our finding that ERK1/2 and ROCKs are common downstream effectors since their activation could also be blocked by AG1478. Our results show for the first time that ErbB2 is an upstream effector of ROCKs and ERK1/2 in mediating diabetes-induced vascular dysfunction. Thus, potential strategies aimed at modifying actions of signal transduction pathways involving ErbB2 pathway may prove to be beneficial in treatment of diabetes-induced vascular complications

Naked Polyamidoamine Polymers Intrinsically Inhibit Angiotensin II-Mediated EGFR and ErbB2 Transactivation in a Dendrimer Generation- and Surface Chemistry-Dependent Manner

The effects of naked polyamidoamine (PAMAM) dendrimers on renin–angiotensin system (RAS) signaling via Angiotensin (Ang) II-mediated transactivation of the epidermal growth factor receptor (EGFR) and the closely related family member ErbB2 (HER2) were investigated. In primary aortic vascular smooth muscle cells, a cationic fifth-generation (G5) PAMAM dendrimer dose- and time-dependently inhibited Ang II/AT₁ receptor-mediated transactivation of EGFR and ErbB2 as well as their downstream signaling via extracellular-regulated kinase 1/2 (ERK1/2). Inhibition even occurred at noncytotoxic concentrations at short (1 h) exposure times and was dependent on dendrimer generation (G7 > G6 > G5 > G4) and surface group chemistry (amino > carboxyl > hydroxyl). Mechanistically, the cationic G5 PAMAM dendrimer inhibited Ang II-mediated transactivation of EGFR and ErbB2 via inhibition of the nonreceptor tyrosine kinase Src. This novel, early onset, intrinsic biological action of PAMAM dendrimers as inhibitors of the Ang II/AT₁/Src/EGFR-ErbB2/ERK1/2 signaling pathway could have important toxicological and pharmacological implications

Ang-(1–7) via its Mas receptor inhibits NE-mediated transactivation of (A) ErbB2 and (B) EGFR receptors in VSMC.

<p>In both A) and B) panel (i) is a representative Western blot showing either the levels of total (t-) or phosphorylated (p-) ErbB2 receptor (Y1221/1222) or EGFR (Y1068) and total β-actin in VSMC grown in normal (5.5 mM) D-glucose (NG), or NG treated with NE (10^-7M) or NE together with 1 micromolar Ang-(1–7) (+ A(1–7), or A(1–7) together with D-Pro⁷-Ang-(1–7) (lane labeled as + A(1–7) +D-Pro), AG1478 (1μM) or AG825 (0.1μM) or 1 micromolar Prazosin (labelled as NE 10⁻⁷ + PRAZ); Panels ii is the densitometry histogram showing ratio levels of stated phosphorylated to total proteins following normalization of each to actin and presented relative to control. N = 5; Mean ± SD. Asterisk (*) indicates significantly different (p<0.05) mean values from NG whereas hash (#) indicates significantly different mean values (p<0.05) from NG at 10^-7M dose.</p

The dose-dependent transactivation of ErbB2 and EGFR receptor by norepinephrine in VSMC can be attenuated by the α_1-adrenergic receptor inhibitor, Prazosin.

<p>Panel (i) is a representative Western blot showing the levels of total (t-) or phosphorylated (p-) ErbB2 receptor (Y1221/1222), EGFR (Y1068) and total β-actin in VSMC grown in normal (5.5 mM) D-glucose (NG), or NG treated with increasing doses of NE or NE (10^-7M) together with 1 micromolar Prazosin (labelled as NE 10⁻⁷ + PRAZ); Panels ii-iii are densitometry histograms showing ratio levels of phosphorylated to total proteins as stated following normalization of each to actin and presented relative to control. N = 5; Mean ± SD. Asterisk (*) indicates significantly different (p<0.05) mean values from NG whereas hash (#) indicates significantly different mean values (p<0.05) from NG at 10^-7M dose.</p

Ang-(1–7) via its Mas receptor inhibits high glucose-induced transactivation of ErbB3 and ErbB4 receptors in VSMC.

<p>Panel (i) is a representative Western blot showing the levels of total (t-) or phosphorylated (p-) ErbB3 (Y1222), ErbB4 (Y1284) receptors and total β-actin in VSMC grown in normal (5.5 mM) D-glucose (NG), or treated with 1 micromolar Ang-(1–7) (labelled as A1-7) or A(1–7) together with D-Pro⁷-Ang-(1–7) (+D-Pro). Panels ii-iii are densitometry histograms showing ratio levels of stated phosphorylated to total protein following normalization of each to actin and presented relative to control. N = 5; Mean ± SD. Asterisk (*) indicates significantly different (p<0.05) mean values from NG whereas hash (#) indicates significantly different mean values (p<0.05) from HG.</p

Diabetes-induced phosphorylation of ErbB2 receptor at multiple tyrosine residues can be attenuated by chronic treatment with Ang-(1–7) or AG825 in the mesenteric bed vasculature of STZ-induced diabetic rats.

<p>Panel i) is a representative Western blot showing the levels of phosphorylated ErbB2 receptor (p-ErbB2) at the indicated tyrosines Y1221/1222, Y1248 (detected by two separate antibodies labeled as Y1248a and Y1248b), and Y877, total ErbB2 receptor (t-ErbB2) and β-actin in the isolated mesenteric bed from normal (non-diabetic) controls (C), diabetic (D) and diabetic animals treated for 4 weeks with either Ang-(1–7) (+A1-7) or AG825 (+AG825). Panels ii)-vii) are densitometry histograms showing band intensity ratios for levels of phosphorylated (at the stated tyrosine residue) and total ErbB2 receptor normalized to actin and presented as relative to control (ii-vi) and ratios of phosphorylated ErbB2 (Y1221/1222) receptor to total ErbB2 receptor following normalization of each to actin and presented as relative to control value (panel vii). n = 6; mean ± SD. Asterisk (*) indicates significantly different (P < 0.05) mean values from normal non-diabetic rats (C), whereas # indicates significantly different mean values (P < 0.05) from diabetic rats (D).</p