Effects of a novel pH-sensitive liposome with cleavable esterase-catalyzed and pH-responsive double smart mPEG lipid derivative on ABC phenomenon

Daquan Chen1,2, Wanhui Liu1,2, Yan Shen3, Hongjie Mu1,2, Yanchun Zhang4 , Rongcai Liang1,2, Aiping Wang1,2, Kaoxiang Sun1,2, Fenghua Fu1,2 1School of Pharmacy, Yantai University, Yantai, People’s Republic of China; 2State Key Laboratory of Long-acting and Targeting Drug Delivery System, Yantai, People’s Republic of China; 3College of Pharmacy, China Pharmaceutical University, Nanjing, People’s Republic of China; 4College of Pharmacy, Anhui University of Traditional Chinese Medicine, Hefei, People’s Republic of China Background: The ABC phenomenon is described as a syndrome of accelerated clearance of polyethylene glycol (PEG)-modified liposomes from the bloodstream when repeatedly injected, with their increased accumulation in the liver and spleen. Methods: To clarify this immune response phenomenon, we evaluated a novel modified pH-sensitive liposome with a cleavable double smart PEG-lipid derivative (mPEG-Hz-CHEMS). Results: The ABC phenomenon in mice was brought about by repeated injection of conventional PEG-PE liposomes and was accompanied by a greatly increased uptake in the liver. However, a slight ABC phenomenon was brought about by repeated injection of mPEG-CHEMS liposomes and was accompanied by only a slightly increased uptake in the liver, and repeated injection of mPEG-Hz-CHEMS liposomes did not induce the ABC phenomenon and there was no increase in liver accumulation. This finding indicates that the cleavable mPEG-Hz-CHEMS derivative could lessen or eliminate the ABC phenomenon induced by repeated injection of PEGylated liposomes. Conclusion: This research has shed some light on a solution to the ABC phenomenon using a cleavable PEG-Hz-CHEMS derivative encapsulated in nanoparticles. Keywords: accelerated blood clearance, double smart, cleavable, mPEG-lipid derivates, pH-sensitive liposom

Deficiency of tPA Exacerbates White Matter Damage, Neuroinflammation, Glymphatic Dysfunction and Cognitive Dysfunction in Aging Mice

Tissue plasminogen activator (tPA) is a serine protease primarily involved in mediating thrombus breakdown and regulating catabolism of amyloid-beta (Abeta). The aim of this study is to investigate age-dependent decline of endogenous tPA and the effects of tPA decline on glymphatic function and cognitive outcome in mice. Male, young (3m), adult (6m) and middle-aged (12m) C57/BL6 (wild type) and tPA knockout (tPA(-/-)) mice were subject to a battery of cognitive tests and white matter (WM) integrity, neuroinflammation, and glymphatic function were evaluated. Adult WT mice exhibit significantly decreased brain tPA level compared to young WT mice and middle-aged WT mice have significantly lower brain tPA levels than young and adult WT mice. Middle-aged WT mice exhibit significant neuroinflammation, reduced WM integrity and increased thrombin deposition compared to young and adult mice, and increased blood brain barrier (BBB) permeability and reduced cognitive ability compared to young WT mice. In comparison to adult WT mice, adult tPA(-/-) mice exhibit significant BBB leakage, decreased dendritic spine density, increased thrombin deposition, neuroinflammation, and impaired functioning of the glymphatic system. Compared to age-matched WT mice, adult and middle-aged tPA(-/-) mice exhibit significantly increased D-Dimer expression and decreased perivascular Aquaporin-4 expression. Compared to age-matched WT mice, young, adult and middle-aged tPA(-/-) mice exhibit significant cognitive impairment, axonal damage, and increased deposition of amyloid precursor protein (APP), Abeta, and fibrin. Endogenous tPA may play an important role in contributing to aging induced cognitive decline, axonal/WM damage, BBB disruption and glymphatic dysfunction in the brain

Recombinant human erythropoietin improves the neurofunctional recovery of rats following traumatic brain injury via an increase in circulating endothelial progenitor cells.

Previous studies show that circulating endothelial progenitor cells (EPCs) promote angiogenesis, which is a process associated with improved recovery in animal models of traumatic brain injury (TBI), and that recombinant human erythropoietin (rhEPO) plays a protective role following stroke. Thus, it was hypothesized that rhEPO would enhance recovery following brain injury in a rat model of TBI via an increase in the mobilization of EPCs and, subsequently, in angiogenesis. Flow cytometry assays using CD34- and CD133-specific antibodies were utilized to identify alterations in EPC levels, CD31 and CD34 antibody-stained brain tissue sections were used to quantify angiogenesis, and the Morris water maze (MWM) test and the modified Neurological Severity Score (mNSS) test were used to evaluate behavioral recovery. Compared with saline treatment, treatment with rhEPO significantly increased the number of circulating EPCs on days 1, 4, 7, and 14 (P < 0.05), improved spatial learning ability on days 24 and 25 (P < 0.05), and enhanced memory recovery on day 26 (P < 0.05). Moreover, rhEPO treatment decreased mNSS assessment scores on days 14, 21, and 25 (P < 0.05). There was a strong correlation between levels of circulating EPCs and CD34- and CD31-positive cells within the injured boundary zone (CD34(+) r = 0.910, P < 0.01; CD31(+) r = 0.894, P < 0.01) and the ipsilateral hippocampus (CD34(+) r = 0.841, P < 0.01; CD31(+) r = 0.835, P < 0.01). The present data demonstrate that rhEPO treatment improved functional outcomes in rats following TBI via an increase in the mobilization of EPCs and in subsequent angiogenesis

Recombinant human erythropoietin improves the neurofunctional recovery of rats following traumatic brain injury via an increase in circulating endothelial progenitor cells.

Previous studies show that circulating endothelial progenitor cells (EPCs) promote angiogenesis, which is a process associated with improved recovery in animal models of traumatic brain injury (TBI), and that recombinant human erythropoietin (rhEPO) plays a protective role following stroke. Thus, it was hypothesized that rhEPO would enhance recovery following brain injury in a rat model of TBI via an increase in the mobilization of EPCs and, subsequently, in angiogenesis. Flow cytometry assays using CD34- and CD133-specific antibodies were utilized to identify alterations in EPC levels, CD31 and CD34 antibody-stained brain tissue sections were used to quantify angiogenesis, and the Morris water maze (MWM) test and the modified Neurological Severity Score (mNSS) test were used to evaluate behavioral recovery. Compared with saline treatment, treatment with rhEPO significantly increased the number of circulating EPCs on days 1, 4, 7, and 14 (P < 0.05), improved spatial learning ability on days 24 and 25 (P < 0.05), and enhanced memory recovery on day 26 (P < 0.05). Moreover, rhEPO treatment decreased mNSS assessment scores on days 14, 21, and 25 (P < 0.05). There was a strong correlation between levels of circulating EPCs and CD34- and CD31-positive cells within the injured boundary zone (CD34(+) r = 0.910, P < 0.01; CD31(+) r = 0.894, P < 0.01) and the ipsilateral hippocampus (CD34(+) r = 0.841, P < 0.01; CD31(+) r = 0.835, P < 0.01). The present data demonstrate that rhEPO treatment improved functional outcomes in rats following TBI via an increase in the mobilization of EPCs and in subsequent angiogenesis

Role of microRNA-126 in vascular cognitive impairment in mice

Vascular dementia (VaD) affects cognition and memory. MicroRNA-126 (miR-126) is an angiogenic microRNA that regulates vascular function. In this study, we employ a multiple microinfarction (MMI) model to induce VaD in mice, and investigate VaD-induced cognitive dysfunction, white matter (WM) damage, glymphatic dysfunction and the role of miR-126 in mediating these effects. Male six-to eight-months old C57/BL6 mice (WT) were subject to MMI model, and cerebral blood flow (CBF), vessel patency, glymphatic function, cognitive function, and serum miR-126 expression were measured. Mice were sacrificed at 28 days after MMI. To investigate the role of miR-126 in VaD, cognitive function, water channel integrity and glymphatic function were assessed in male, six-to eight months old conditional-knockout endothelial cell miR-126 (miR-12