CUL5-Mediated Visfatin (NAMPT) Degradation Blocks Endothelial Proliferation and Angiogenesis via the MAPK/PI3K-AKT Signaling

Acute severe hypoglycemia alters mouse brain microvascular proteome

Hypoglycemia increases the risk related to stroke and neurodegenerative diseases, however, the underlying mechanisms are unclear. For the first time, we studied the effect of a single episode (acute) of severe (ASH) and mild (AMH) hypoglycemia on mouse brain microvascular proteome. After four-hour fasting, insulin was administered (i.p) to lower mean blood glucose in mice and induce ∼30 minutes of ASH (∼30 mg/dL) or AMH (∼75 mg/dL), whereas a similar volume of saline was given to control mice (∼130 mg/dL). Blood glucose was allowed to recover over 60 minutes either spontaneously or by 20% dextrose administration (i.p). Twenty-four hours later, the brain microvessels (BMVs) were isolated, and tandem mass tag (TMT)-based quantitative proteomics was performed using liquid chromatography-mass spectrometry (LC/MS). When compared to control, ASH significantly downregulated 13 proteins (p ≤ 0.05) whereas 23 proteins showed a strong trend toward decrease (p ≤ 0.10). When compared to AMH, ASH significantly induced the expression of 35 proteins with 13 proteins showing an increasing trend. AMH downregulated only 3 proteins. ASH-induced downregulated proteins are involved in actin cytoskeleton maintenance needed for cell shape and migration which are critical for blood-brain barrier maintenance and angiogenesis. In contrast, ASH-induced upregulated proteins are RNA-binding proteins involved in RNA splicing, transport, and stability. Thus, ASH alters BMV proteomics to impair cytoskeletal integrity and RNA processing which are critical for cerebrovascular function.

Forkhead box A1 induces angiogenesis through activation of the S100A8/p38 MAPK axis in cutaneous wound healing

BACKGROUND

The association between S100 calcium-binding protein A8 (S100A8) and angiogenesis has been reported in previous reports. This study focuses on the roles of S100A8 in the angiogenesis of human dermal microvascular endothelial cells (HDMECs) and in cutaneous wound healing in mice.

METHODS

Candidate genes related to angiogenesis activity were screened using a GSE83582 dataset. The overexpression DNA plasmid of S100A8 was transfected into HDMECs to analyze its effect on cell proliferation, migration, and angiogenesis. Full-thickness skin wounds were induced on mice, followed by adenovirus treatments to analyze the function of gene alteration in wound healing and pathological changes. The upstream regulator of S100A8 was predicted by bioinformatics analysis and verified by luciferase and immunoprecipitation assays. The role of the forkhead box A1 (FOXA1)-S100A8 interaction in p38 MAPK activation and angiogenesis were validated by rescue experiments.

RESULTS

S100A8 was identified as a gene significantly correlated with angiogenesis. The S100A8 upregulation promoted the proliferation, migration, and angiogenesis of HDMECs, and it promoted p38 MAPK phosphorylation. Treatment of SB203580, a p38 MAPK inhibitor, blocked the promoting effect of S100A8. FOXA1 was identified as an upstream factor of S100A8 promoting its transcription. FOXA1 overexpression in HDMECs increased p38 MAPK phosphorylation and enhanced the activity of cells, which were blocked by the S100A8 inhibition. Similar results were reproduced in vivo where FOXA1 overexpression accelerated whereas the S100A8 knockdown retarded the cutaneous wound healing in mice.

CONCLUSION

FOXA1 mediates the phosphorylation of p38 MAPK through transcription activation of S100A8, thereby inducing angiogenesis and promoting cutaneous wound healing.

Activated SIRT1 contributes to DPT-induced glioma cell parthanatos by upregulation of NOX2 and NAT10

Parthanatos is a type of programmed cell death dependent on hyper-activation of poly (ADP-ribose) polymerase 1 (PARP-1). SIRT1 is a highly conserved nuclear deacetylase and often acts as an inhibitor of parthanatos by deacetylation of PARP1. Our previous study showed that deoxypodophyllotoxin (DPT), a natural compound isolated from the traditional herb Anthriscus sylvestris, triggered glioma cell death via parthanatos. In this study, we investigated the role of SIRT1 in DPT-induced human glioma cell parthanatos. We showed that DPT (450 nmol/L) activated both PARP1 and SIRT1, and induced parthanatos in U87 and U251 glioma cells. Activation of SIRT1 with SRT2183 (10 μmol/L) enhanced, while inhibition of SIRT1 with EX527 (200 μmol/L) or knockdown of SIRT1 attenuated DPT-induced PARP1 activation and glioma cell death. We demonstrated that DPT (450 nmol/L) significantly decreased intracellular NAD+ levels in U87 and U251 cells. Further decrease of NAD+ levels with FK866 (100 μmol/L) aggravated, but supplement of NAD+ (0.5, 2 mmol/L) attenuated DPT-induced PARP1 activation. We found that NAD+ depletion enhanced PARP1 activation via two ways: one was aggravating ROS-dependent DNA DSBs by upregulation of NADPH oxidase 2 (NOX2); the other was reinforcing PARP1 acetylation via increase of N-acetyltransferase 10 (NAT10) expression. We found that SIRT1 activity was improved when being phosphorylated by JNK at Ser27, the activated SIRT1 in reverse aggravated JNK activation via upregulating ROS-related ASK1 signaling, thus forming a positive feedback between JNK and SIRT1. Taken together, SIRT1 activated by JNK contributed to DPT-induced human glioma cell parthanatos via initiation of NAD+ depletion-dependent upregulation of NOX2 and NAT10.