Human plasminogen-derived N-acetyl-Arg-Leu-Tyr-Glu antagonizes VEGFR-2 to prevent blood-retinal barrier breakdown in diabetic mice

Exploring the mechanism of Bushen Huoxue prescription in the treatment of early diabetic retinal edema from the perspective of inner blood-retinal barrier injury

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic retinopathy (DR) is one of the most severe complications of diabetes mellitus, diabetes belongs to the category of "emaciation-thirst disease" in traditional Chinese medicine (TCM). Bushen Huoxue Prescription (BHP) is composed of traditional Chinese materia medica, which has therapeutic effects on DR and early diabetic retinal edema (EDRE). However, the therapeutic mechanism is unclear.

AIM OF THE STUDY

Exploring the mechanism of BHP against EDRE.

METHODS

Feeding Sprague Dawley (SD) rats a high-fat, high-sugar diet as well as providing intraperitoneal injections of streptozotocin (STZ) to promote inner blood-retinal barrier (iBRB) damage that can trigger EDRE, evaluating the therapeutic effect of BHP by the level of expressiveness of TJ proteins (ZO-1,Occludin) of the iBRB and the leakage of rhodamine B isothiocyanate (RITC) in the retina. The combination of network pharmacology and metabolomics was employed to study the mechanism of BHP in preventing of EDRE, then four proteins which were closely to the damage of iBRB were chosen for the validation by employing Western Blot (WB).

RESULTS

Research of network pharmacology had shown that BHP had efficacy against EDRE by regulating targets such as AKT1, ALB, TNF, PPARG, etc, its potential pathways mainly involving signaling pathways such as HIF-1. In untargeted metabolomics analysis of serum, 15 differential metabolites were identified, with the metabolic pathways focusing on ketone body metabolism and synthesis, sphingolipid metabolism and phenylalanine metabolism. The conclusions of metabolomics and network pharmacology revealed that BHP can treat EDRE by alleviating hypoxia and oxidative stress and exerting protection of the iBRB. Finally, BHP's protection behavior of the iBRB was validated by WB experiments.

CONCLUSION

Through integrating pharmacodynamics, network pharmacology and metabolomics, BHP was discovered to have a crucial function in EDRE therapy by preserving the integrity of iBRB. This comprehensive strategy also provided a reasonable way to reveal the multi-components, multi-targets, multi-pathways mechanism of TCM.

Screening, characterization and specific binding mechanism of aptamers against human plasminogen Kringle 5

Plasminogen Kringle 5 is one of the most potent cytokines identified to inhibit the proliferation and migration of vascular endothelial cells. Herein, six aptamer candidates that specifically bind to Kringle 5 were generated by the systematic evolution of ligands by exponential enrichment (SELEX). After 10 rounds of screening against Kringle 5, a highly enriched ssDNA pool was sequenced and the representative aptamers were subjected to binding assays to evaluate their affinity and specificity. The preferred aptamer KG-4, which demonstrated a low dissociation constant (K_d) of ∼ 432 nM and excellent selectivity for Kringle 5. A conserved "motif" of eight bases located at the stem-loop intersection, common to the aptamer, was further confirmed as the recognition element for binding with Kringle 5. The bulge formed by the motif and depression on the lysine binding site of Kringle 5 were both located at the binding interface, and the "induced fit" between their structures played a central role in the recognition process. Kringle 5 interacts KG-4 primarily through enthalpy-driven van der Waals forces and hydrogen bond. The key nucleotides A34 and C35 at motif on KG-4 and the positively charged amino acids in the loop 1 and loop 4 regions on Kringle 5 play a major role in the interaction. Furthermore, KG-4 dose-dependently reduced the proliferation inhibition of vascular endothelial cells by Kringle 5 and had a blocking effect on the function of Kringle 5 in inhibiting migration and promoting apoptosis of vascular endothelial cells in vitro. This study put a new light on protein-aptamer binding mechanism and may provide insight into the treatment of ischemic diseases by target depletion of Kringle 5.

Diabetic retinopathy: Involved cells, biomarkers, and treatments

Diabetic retinopathy (DR), a leading cause of vision loss and blindness worldwide, is caused by retinal neurovascular unit dysfunction, and its cellular pathology involves at least nine kinds of retinal cells, including photoreceptors, horizontal and bipolar cells, amacrine cells, retinal ganglion cells, glial cells (Müller cells, astrocytes, and microglia), endothelial cells, pericytes, and retinal pigment epithelial cells. Its mechanism is complicated and involves loss of cells, inflammatory factor production, neovascularization, and BRB impairment. However, the mechanism has not been completely elucidated. Drug treatment for DR has been gradually advancing recently. Research on potential drug targets relies upon clear information on pathogenesis and effective biomarkers. Therefore, we reviewed the recent literature on the cellular pathology and the diagnostic and prognostic biomarkers of DR in terms of blood, protein, and clinical and preclinical drug therapy (including synthesized molecules and natural molecules). This review may provide a theoretical basis for further DR research.

Wnt Signaling in Inner Blood-Retinal Barrier Maintenance

The retina is a light-sensing ocular tissue that sends information to the brain to enable vision. The blood-retinal barrier (BRB) contributes to maintaining homeostasis in the retinal microenvironment by selectively regulating flux of molecules between systemic circulation and the retina. Maintaining such physiological balance is fundamental to visual function by facilitating the delivery of nutrients and oxygen and for protection from blood-borne toxins. The inner BRB (iBRB), composed mostly of inner retinal vasculature, controls substance exchange mainly via transportation processes between (paracellular) and through (transcellular) the retinal microvascular endothelium. Disruption of iBRB, characterized by retinal edema, is observed in many eye diseases and disturbs the physiological quiescence in the retina's extracellular space, resulting in vision loss. Consequently, understanding the mechanisms of iBRB formation, maintenance, and breakdown is pivotal to discovering potential targets to restore function to compromised physiological barriers. These unraveled targets can also inform potential drug delivery strategies across the BRB and the blood-brain barrier into retinas and brain tissues, respectively. This review summarizes mechanistic insights into the development and maintenance of iBRB in health and disease, with a specific focus on the Wnt signaling pathway and its regulatory role in both paracellular and transcellular transport across the retinal vascular endothelium.

Expression and role of P-element-induced wimpy testis-interacting RNA in diabetic-retinopathy in mice

BACKGROUND

As one of the major microvascular complications of diabetes, diabetic retinopathy (DR) is the leading cause of blindness in the working age population. Because the extremely complex pathogenesis of DR has not been fully clarified, the occurrence and development of DR is closely related to tissue ischemia and hypoxia and neovascularization The formation of retinal neovascularization (RNV) has great harm to the visual acuity of patients.

AIM

To investigate the expression of P-element-induced wimpy testis-interacting RNA (piRNA) in proliferative DR mice and select piRNA related to RNV.

METHODS

One hundred healthy C57BL/6J mice were randomly divided into a normal group as control group (CG) and proliferative DR (PDR) group as experimental group (EG), with 50 mice in each group. Samples were collected from both groups at the same time, and the lesions of mice were evaluated by hematoxylin and eosin staining and retinal blood vessel staining. The retinal tissues were collected for second-generation high-throughput sequencing, and the differentially expressed piRNA between the CG and EG was detected, and polymerase chain reaction (PCR) was conducted for verification. The differentially obtained piRNA target genes and expression profiles were enrichment analysis based on gene annotation (Gene Ontology) and Kyoto Encyclopedia of Genes and Genomes.

RESULTS

In the CG there was no perfusion area, neovascularization and endothelial nucleus broke through the inner boundary membrane of retinap. In the EG, there were a lot of nonperfused areas, new blood vessels and endothelial nuclei breaking through the inner boundary membrane of the retina. There was a statistically significant difference in the number of vascular endothelial nuclei breaking through the inner retinal membrane between the two groups. High-throughput sequencing analysis showed that compared with the CG, a total of 79 piRNAs were differentially expressed in EG, among which 43 piRNAs were up-regulated and 36 piRNAs were down-regulated. Bioinformatics analysis showed that the differentially expressed piRNAs were mainly concentrated in the signaling pathways of angiogenesis and cell proliferation. Ten piRNAs were selected for PCR, and the results showed that the expression of piR-MMU-40373735, piR-MMU-61121420, piR-MMU-55687822, piR-MMU-1373887 were high, and the expression of piR-MMU-7401535, piR-MMU-4773779, piR-MMU-1304999, and piR-MMU-5160126 were low, which were consistent with the sequencing results.

CONCLUSION

In the EG, the abnormal expression of piRNA is involved in the pathway of angiogenesis and cell proliferation, suggesting that piRNAs have some regulatory function in proliferative diabetic-retinopathy.