Netrin-4 expression by human endothelial cells inhibits endothelial inflammation and senescence

Crosstalk in skin: Loss of desmoglein 1 in keratinocytes inhibits BRAFV600E-induced cellular senescence in human melanocytes

Melanoma arises from transformation of melanocytes in the basal layer of the epidermis where they are surrounded by keratinocytes, with which they interact through cell contact and paracrine communication. Considerable effort has been devoted to determining how the accumulation of oncogene and tumor suppressor gene mutations in melanocytes drive melanoma development. However, the extent to which alterations in keratinocytes that occur in the developing tumor niche serve as extrinsic drivers of melanoma initiation and progression is poorly understood. We recently identified the keratinocyte-specific cadherin, desmoglein 1 (Dsg1), as an important mediator of keratinocyte:melanoma cell crosstalk, demonstrating that its chronic loss, which can occur through melanoma cell-dependent paracrine signaling, promotes behaviors that mimic a malignant phenotype. Here we address the extent to which Dsg1 loss affects early steps in melanomagenesis. RNA-Seq analysis revealed that paracrine signals from Dsg1-deficient keratinocytes mediate a transcriptional switch from a differentiated to undifferentiated cell state in melanocytes expressing BRAFV600E, a driver mutation commonly present in both melanoma and benign nevi and reported to cause growth arrest and oncogene-induced senescence (OIS). Of ~220 differentially expressed genes in BRAFV600E cells treated with Dsg1-deficient conditioned media (CM), the laminin superfamily member NTN4/Netrin-4, which inhibits senescence in endothelial cells, stood out. Indeed, while BRAFV600E melanocytes treated with Dsg1-deficient CM showed signs of senescence bypass as assessed by increased senescence-associated β-galactosidase activity and decreased p16, knockdown of NTN4 reversed these effects. These results suggest that Dsg1 loss in keratinocytes provides an extrinsic signal to push melanocytes towards oncogenic transformation once an initial mutation has been introduced.

Laminin N-terminus (LaNt) proteins, laminins and basement membrane regulation

Basement membranes (BMs) are structured regions of the extracellular matrix that provide multiple functions including physical support and acting as a barrier, as a repository for nutrients and growth factors, and as biophysical signalling hubs. At the core of all BMs is the laminin (LM) family of proteins. These large heterotrimeric glycoproteins are essential for tissue integrity, and differences between LM family members represent a key nexus in dictating context and tissue-specific functions. These variations reflect genetic diversity within the family, which allows for multiple structurally and functionally distinct heterotrimers to be produced, each with different architectures and affinities for other matrix proteins and cell surface receptors. The ratios of these LM isoforms also influence the biophysical properties of a BM owing to differences in their relative ability to form polymers or networks. Intriguingly, the LM superfamily is further diversified through the related netrin family of proteins and through alternative splicing leading to the generation of non-LM short proteins known as the laminin N-terminus (LaNt) domain proteins. Both the netrins and LaNt proteins contain structural domains involved in LM-to-LM interaction and network assembly. Emerging findings indicate that one netrin and at least one LaNt protein can potently influence the structure and function of BMs, disrupting the networks, changing physical properties, and thereby influencing tissue function. These findings are altering the way that we think about LM polymerisation and, in the case of the LaNt proteins, suggest a hitherto unappreciated form of LM self-regulation.

Recent Advances in Senotherapeutics Delivery

Accumulation of senescent cells (SnCs) in various tissue types has been connected to an occurrence of different age-related diseases that are indicated by its own tissue-specific hallmarks. Discovery of novel senolytic compounds that target major cellular mechanisms to inhibit the level of SnCs within the specific tissues or organs has been an emerging field in the age-related disease research. Although the positive effect of senolytics in global suppression of SnCs has been well studied in the past, effective tissue-specific delivery strategy of senotherapeutics before clinical application needs to be further investigated. In this review, we discuss the latest biological insights to currently available senotherapeutic options and explore the impactful in vitro tissue-engineered models possibly as a testbed for replicable testing of tissue-specific potency of senolytics. Impact statement Senotherapy, the inhibition of accumulated senescent cells, is recognized as a significantly impactful way to treat various human diseases. However, there is limited comprehensive reviews on this topic. This review provides in-depth discussion on diverse delivery strategies of senolytic agents and latest updates on a novel senotherapeutic research.

Association between serum netrin-1, netrin-4 and risk of the acute coronary syndrome in patients with type 2 diabetes mellitus-A pilot study

The present study was done to assess the diagnostic utility of serum netrin-1 and netrin-4 for recognising the acute coronary syndrome (ACS) in type 2 diabetes mellitus (T2DM) patients. Forty-two T2DM patients with ACS (Cases) and forty-two T2DM patients without ACS (Controls) were compared. Cases had lower serum netrin-1 and netrin-4 levels than controls and were negatively associated with creatinine kinase-total, creatinine kinase-MB, troponin-T and H-FABP. ROC analysis showed that netrin-1 and netrin-4 had good sensitivity and specificity for ACS prediction in T2DM patients. Serum netrin-1 and netrin-4 levels might be considered complementary markers for ACS diagnosis in T2DM patients.

Anti-Inflammatory Role of Netrin-4 in Diabetic Retinopathy

Diabetic retinopathy is characterized by dysfunction of the retinal vascular network, combined with a persistent low-grade inflammation that leads to vision-threatening complications. Netrin-4 (NTN4) is a laminin-related secreted protein and guidance cue molecule present in the vascular basal membrane and highly expressed in the retina. A number of studies inferred that the angiogenic abilities of NTN4 could contribute to stabilize vascular networks and modulate inflammation. Analyzing human specimens, we show that NTN4 and netrin receptors are upregulated in the diabetic retina. We further evaluated a knock-out model for NTN4 undergoing experimental diabetes induced by streptozotocin. We investigated retina function and immune cells in vivo and demonstrated that NTN4 provides a protective milieu against inflammation in the diabetic retina and prevents cytokine production.