Gamma-secretase regulates VEGFR-1 signalling in vascular endothelium and RPE

Amorphous selenium nanodots alleviate non-alcoholic fatty liver disease via activating VEGF receptor 1 to further inhibit phosphorylation of JNK/p38 MAPK pathways

In clinic, there is still no unified standard for the treatment of non-alcoholic fatty liver disease (NAFLD), and the development of effective novel drugs to alleviate NAFLD remains a challenge. This study aimed to explore the effect and mechanism of amorphous selenium nanodots (A SeNDs) in alleviating NAFLD. Model rats with NAFLD were induced by the high-fat diet (HFD). Histomorphology was used to observe liver tissue, automatic biochemical analyzer was used to analyze liver function indicators, and ELISA kit was used to detect the effect of A SeNDs on oxidative stress and inflammatory factors in NAFLD rats. The results exhibited that A SeNDs could reduce hepatocyte steatosis, liver index, blood lipid level, and transaminase level in NAFLD rats. Furthermore, A SeNDs could relieve the oxidative stress and inflammatory reaction and maintain liver tissue structure in NAFLD rats. Mechanistically, A SeNDs (0.3 mg/kg/day) inhibit the phosphorylation of JNK/p38 MAPK pathways after activating vascular endothelial growth factor receptor 1 (VEGFR1) in the liver of rats with NAFLD to allay oxidative stress and inflammatory response and improves hepatic structure and liver function. Therefore, it should be an important method to mitigate NAFLD by supplementing A SeNDs to normalize hepatic structure and liver function.

Nanocomposite scaffolds for accelerating chronic wound healing by enhancing angiogenesis

Skin is the body's first barrier against external pathogens that maintains the homeostasis of the body. Any serious damage to the skin could have an impact on human health and quality of life. Tissue engineering aims to improve the quality of damaged tissue regeneration. One of the most effective treatments for skin tissue regeneration is to improve angiogenesis during the healing period. Over the last decade, there has been an impressive growth of new potential applications for nanobiomaterials in tissue engineering. Various approaches have been developed to improve the rate and quality of the healing process using angiogenic nanomaterials. In this review, we focused on molecular mechanisms and key factors in angiogenesis, the role of nanobiomaterials in angiogenesis, and scaffold-based tissue engineering approaches for accelerated wound healing based on improved angiogenesis.

Brain expression of the vascular endothelial growth factor gene family in cognitive aging and alzheimer's disease

Vascular endothelial growth factor (VEGF) is associated with the clinical manifestation of Alzheimer's disease (AD). However, the role of the VEGF gene family in neuroprotection is complex due to the number of biological pathways they regulate. This study explored associations between brain expression of VEGF genes with cognitive performance and AD pathology. Genetic, cognitive, and neuropathology data were acquired from the Religious Orders Study and Rush Memory and Aging Project. Expression of ten VEGF ligand and receptor genes was quantified using RNA sequencing of prefrontal cortex tissue. Global cognitive composite scores were calculated from 17 neuropsychological tests. β-amyloid and tau burden were measured at autopsy. Participants (n = 531) included individuals with normal cognition (n = 180), mild cognitive impairment (n = 148), or AD dementia (n = 203). Mean age at death was 89 years and 37% were male. Higher prefrontal cortex expression of VEGFB, FLT4, FLT1, and PGF was associated with worse cognitive trajectories (p ≤ 0.01). Increased expression of VEGFB and FLT4 was also associated with lower cognition scores at the last visit before death (p ≤ 0.01). VEGFB, FLT4, and FLT1 were upregulated among AD dementia compared with normal cognition participants (p ≤ 0.03). All four genes associated with cognition related to elevated β-amyloid (p ≤ 0.01) and/or tau burden (p ≤ 0.03). VEGF ligand and receptor genes, specifically genes relevant to FLT4 and FLT1 receptor signaling, are associated with cognition, longitudinal cognitive decline, and AD neuropathology. Future work should confirm these observations at the protein level to better understand how changes in VEGF transcription and translation relate to neurodegenerative disease.

Irreversible modifications of receptor tyrosine kinases

Each group of the 56 receptor tyrosine kinases (RTK) binds with one or more soluble growth factors and coordinates a vast array of cellular functions. These outcomes are tightly regulated by inducible post-translational events, such as tyrosine phosphorylation, ubiquitination, ectodomain shedding, and regulated intramembrane proteolysis. Because of the delicate balance required for appropriate RTK function, cells may become pathogenic upon dysregulation of RTKs themselves or their post-translational covalent modifications. For example, reduced ectodomain shedding and decreased ubiquitination of the cytoplasmic region, both of which enhance growth factor signals, characterize malignant cells. Whereas receptor phosphorylation and ubiquitination are reversible, proteolytic cleavage events are irreversible, and either modification might alter the subcellular localization of RTKs. Herein, we focus on ectodomain shedding by metalloproteinases (including ADAM family proteases), cleavage within the membrane or cytoplasmic regions of RTKs (by gamma-secretases and caspases, respectively), and complete receptor proteolysis in lysosomes and proteasomes. Roles of irreversible modifications in RTK signaling, pathogenesis, and pharmacology are highlighted.

Ablation of endothelial VEGFR1 improves metabolic dysfunction by inducing adipose tissue browning

Angiogenesis plays an instrumental role in the modulation of adipose tissue mass and metabolism. Targeting adipose vasculature provides an outstanding opportunity for treatment of obesity and metabolic disorders. Here, we report the physiological functions of VEGFR1 in the modulation of adipose angiogenesis, obesity, and global metabolism. Pharmacological inhibition and genetic deletion of endothelial VEGFR1 augmented adipose angiogenesis and browning of subcutaneous white adipose tissue, leading to elevated thermogenesis. In a diet-induced obesity model, endothelial-VEGFR1 deficiency demonstrated a potent anti-obesity effect by improving global metabolism. Along with metabolic changes, fatty liver and insulin sensitivity were also markedly improved in VEGFR1-deficient high fat diet (HFD)-fed mice. Together, our data indicate that targeting of VEGFR1 provides an exciting new opportunity for treatment of obesity and metabolic diseases, such as liver steatosis and type 2 diabetes.

VEGFR2 alteration in Alzheimer's disease

Alzheimer’s disease (AD) is a common disorder of progressive cognitive decline among elderly subjects. Angiogenesis-related factors including vascular endothelial growth factor (VEGF) might be involved in the pathogenesis of AD. Soluble form of the VEGF receptor is likely to be an intrinsic negative counterpart of VEGF. We measured the plasma levels of VEGF and its two soluble receptors (sVEGFR1 and sVEGFR2) in 120 control subjects, 75 patients with mild cognitive impairment, and 76 patients with AD using ELISA. Plasma levels of VEGF in patients with AD were higher than those in healthy control subjects. However, plasma levels of sVEGFR1 and sVEGFR2 were lower in patients with AD than in healthy control subjects. Levels of VEGFR2 mRNA were significantly decreased in human umbilical vein endothelial cells after amyloid-beta treatment. Further, protein levels of VEGFR2 were also decreased in the brains of AD model mice. In addition, we show that the expression of sVEGFR2 and VEGFR2 was also decreased by the transfection with the Notch intracellular domain. These results indicate that the alterations of VEGF and its two receptors levels might be associated with those at risk for Alzheimer’s disease.

β-Secretase (BACE1) inhibition causes retinal pathology by vascular dysregulation and accumulation of age pigment

β-Secretase (BACE1) is a major drug target for combating Alzheimer's disease (AD). Here we show that BACE1(-/-) mice develop significant retinal pathology including retinal thinning, apoptosis, reduced retinal vascular density and an increase in the age pigment, lipofuscin. BACE1 expression is highest in the neural retina while BACE2 was greatest in the retinal pigment epithelium (RPE)/choroid. Pigment epithelial-derived factor, a known regulator of γ-secretase, inhibits vascular endothelial growth factor (VEGF)-induced in vitro and in vivo angiogenesis and this is abolished by BACE1 inhibition. Moreover, intravitreal administration of BACE1 inhibitor or BACE1 small interfering RNA (siRNA) increases choroidal neovascularization in mice. BACE1 induces ectodomain shedding of vascular endothelial growth factor receptor 1 (VEGFR1) which is a prerequisite for γ-secretase release of a 100 kDa intracellular domain. The increase in lipofuscin following BACE1 inhibition and RNAI knockdown is associated with lysosomal perturbations. Taken together, our data show that BACE1 plays a critical role in retinal homeostasis and that the use of BACE inhibitors for AD should be viewed with extreme caution as they could lead to retinal pathology and exacerbate conditions such as age-related macular degeneration.

Elevated amyloid β production in senescent retinal pigment epithelium, a possible mechanism of subretinal deposition of amyloid β in age-related macular degeneration

Age-related macular degeneration (AMD) is the most common cause of legal blindness in the elderly individuals in developed countries. Subretinally-deposited amyloid β (Aβ) is a main contributor of developing AMD. However, the mechanism causing Aβ deposition in AMD eyes is unknown. Aging is the most significant risk of AMD, thus, we examined the effect of aging on subretinal Aβ deposition. mRNAs and cell lysates were isolated from retinal pigment epithelial (RPE) cells derived from 24-month-old (24M RPE) and 2-month-old (2M RPE) C57BL/6 mice. Aβ concentration in culture supernatants was measured by ELISA. Activity and expression of proteins that regulate Aβ level were examined by activity assay and real time PCR. Effect of β-secretase (BACE) on Aβ production was examined by siRNA silencing. Aβ amounts in supernatants of 24M RPE were significantly higher than 2M RPE. Activity and mRNA levels of neprilysin, an Aβ degrading enzyme, were significantly decreased in 24M RPE compared to 2M RPE. PCR analysis found that BACE2 was significantly more abundantly expressed than BACE1 in RPE cells, however, inactivation of BACE2 gene did not affect Aβ production. BACE1 protein amounts did not differ between 24M and 2M RPE, however, BACE1 activity was significantly higher in 24M RPE compared to 2M RPE. There were no significant changes in the activities of α- or γ-secretase between 2M and 24M RPE. In conclusion, RPE cells produce more amounts of Aβ when they are senescent, and this is probably caused by a decrease in Aβ degradation due to a reduction in the expression and activity of neprilysin and an increase in Aβ synthesis due to increased activity of BACE1.

New treatment options in the management of glioblastoma multiforme: a focus on bevacizumab

Glioblastoma multiforme (GBM) is the most common malignant primary brain tumor in adults and carries the poorest prognosis. Despite recent progress in molecular biology, neuro-imaging and neuro-surgical care, the management of patients with GBM continues to harbor significant challenges. Survival after diagnosis is poor even with the most aggressive approach using multimodality therapy. Although the etiology of malignant gliomas is not known, the dependency of tumor growth on angiogenesis has identified this pathway as a promising therapeutic target. Bevacizumab was the first antiangiogenic therapy approved for use in cancer and received accelerated Food and Drug Administration approval for the treatment of recurrent GBM in 2009, the first new drug for this disease in over a decade. This review describes the rationale behind the treatment of GBM with bevacizumab. The pharmacology, efficacy, safety and tolerability of bevacizumab will also be reviewed.

Brain angiogenesis in developmental and pathological processes: mechanism and therapeutic intervention in brain tumors

Formation of new blood vessels is required for the growth and metastasis of all solid tumors. New blood vessels are established in tumors mainly through angiogenesis. Brain tumors in particular are highly angiogenic. Therefore, interventions designed to prevent angiogenesis may be effective at controlling brain tumors. Indeed, many recent findings from preclinical and clinical studies of antiangiogenic therapy for brain tumors have shown that it is a promising approach to managing this deadly disease, especially when combined with other cytotoxic treatments. In this minireview, we summarize the basic characteristics of brain tumor angiogenesis and the role of known angiogenic factors in regulating this angiogenesis, which may be targets of antiangiogenic therapy. We also discuss the current status of antiangiogenic therapy for brain tumors, the suggested mechanisms of this therapy and the limitations of this strategy.