Resveratrol and related stilbene derivatives induce stress granules with distinct clearance kinetics

Stress granules (SGs) are ribonucleoprotein functional condensates that form under stress conditions in all eukaryotic cells. Although their stress-survival function is far from clear, SGs have been implicated in the regulation of many vital cellular pathways. Consequently, SG dysfunction is thought to be a mechanistic point of origin for many neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS). Additionally, SGs are thought to play a role in pathogenic pathways as diverse as viral infection and chemotherapy resistance. There is a growing consensus on the hypothesis that understanding the mechanistic regulation of SG physical properties is essential to understanding their function. Although the internal dynamics and condensation mechanisms of SGs have been broadly investigated, there have been fewer investigations into the timing of SG formation and clearance in live cells. Because the lifetime of SG persistence can be a key factor in their function and tendency toward pathological dysregulation, SG clearance mechanisms deserve particular attention. Here we show that resveratrol and its analogues piceatannol, pterostilbene, and 3,4,5,4'-tetramethoxystilbene induce G3BP-dependent SG formation with atypically rapid clearance kinetics. Resveratrol binds to G3BP, thereby reducing its protein-protein association valency. We suggest that altering G3BP valency is a pathway for the formation of uniquely transient SGs.

Transcriptome Analysis of Hypoxic Lymphatic Endothelial Cells Indicates Their Potential to Contribute to Extracellular Matrix Rearrangement

Lymphedema (LE) affects millions of people worldwide. It is a chronic progressive disease with massive development of fibrosclerosis when untreated. There is no pharmacological treatment of lymphedema. The disease is associated with swelling of the interstitium of the affected organ, mostly arm or leg, impressive development of adipose tissue, fibrosis and sclerosis with accumulation of huge amounts of collagen, and Papillomatosis cutis. Malnutrition and reduced oxygenation of the affected tissues is a hallmark of lymphedema. Here, we investigated if the hypoxia of lymphatic endothelial cells (LECs) might contribute to fibrosis. We applied RNASeq and qPCR to study the concordant changes of the exome of three human foreskin-derived LEC isolates after 4 days of hypoxia (1% O₂) vs. normoxia (21% O₂). Of the approximately 16,000 genes expressed in LECs, 162 (1%) were up- or down-regulated by hypoxia. Of these, 21 genes have important functions in the production or modification of the extracellular matrix (ECM). In addition to the down-regulation of elastin, we found up-regulation of druggable enzymes and regulators such as the long non-coding RNA H19, inter-alpha-trypsin inhibitor heavy chain family member 5 (ITIH5), lysyl-oxidase (LOX), prolyl 4-hydroxylase subunit alpha 1 (P4HA1), procollagen-lysine 2-oxoglutarate 5-dioxygenase 2 (PLOD2), and others that are discussed in the paper. Initial lymphatics do not produce a continuous basement membrane; however, our study shows that hypoxic LECs have an unexpectedly high ability to alter the ECM.

Absence of lymphatic vessels in term placenta

Background

There has been debate about the existence of lymphatic vessels in placenta. Lymphatic endothelial cell (LEC) markers such as LYVE-1 and podoplanin/D2–40 have been found, although PROX1 has not been detected. The most reliable marker for LECs is the double staining for CD31 and PROX1, which has not been performed yet.

Methods

We studied three term placentas and dissected them into three areas: i.) basal plate area, ii.) intermediate area, and iii.) chorionic plate area. We used immunofluorescence single and double staining with antibodies against CD31, PROX1, LYVE-1, VEGFR-3, D2–40/PDPN, CD34, CCBE-1, and vimentin, as well as nested PCR, qPCR, Western blot and transmission electron microscopy (TEM).

Results

At TEM level we observed structures that have previously mistakenly been interpreted as lymphatics, however, we did not find any CD31/PROX1 double-positive cells in placenta. Absence of PROX1 was also noted by nested PCR, qPCR and Western blot. Also, LEC marker VEGFR-3 was expressed only in a small number of scattered leukocytes but was absent from vessels. The LEC marker D2–40/PDPN was expressed in most stromal cells, and the LEC marker LYVE-1 was found in a considerable number of stromal cells, but not in endothelial cells, which were positive for CD31, CD34, CCBE-1 and vimentin. Additionally, vimentin was found in stromal cells.

Conclusions

Our studies clearly show absence of lymphatics in term placenta. We also show that the functional area of the mother’s endometrium is not penetrated by lymphatics in term pregnancy.

The lymphangiogenesis inhibitor esVEGFR-2 in human embryos: expression in sympatho-adrenal tissues and differentiation-induced up-regulation in neuroblastoma

Tumour-induced hem- and lymph-angiogenesis are frequently associated with tumour progression. Vascular endothelial growth factor-C (VEGF-C) is a potent inducer of lymphangiogenesis, while the endogenous soluble splice-variant of VEGF receptor-2, esVEGFR-2, acts as a natural inhibitor. Previously we have shown down-regulation of esVEGFR-2 mRNA in progressed stages of neuro-blastoma (NB), a tumour derived from sympatho-adrenal precursor cells. Here we studied the immunolocalization of esVEGFR-2 in human embryos, infantile adrenal gland and primary NB. We also quantified esVEGFR-2 mRNA in NB cell lines after differentiation-induction by all-trans retinoic acid (ATRA). By immunoperoxidase staining we observed expression of esVEGFR-2 in both the sympathetic trunk and the adrenal medulla. Additionally, esVEGFR-2 was found in spinal ganglia, floor plate of the neural tube, choroid plexus, notochord, arterial endothelium, skeletal muscle, epidermis and gut epithelium. Developing and circulating leukocytes showed the strongest signal. In NB, esVEGFR-2 was considerably stronger in differentiating low grade tumours with neuronal phenotype than in undifferentiated lesions. Differentiation-induction of the NB cell line SMS-Kan with 5-10 µM ATRA resulted in a significant increase of esVEGFR-2 mRNA after 6, 9 and 12 days. We show that esVEGFR-2 is widely expressed in embryonic tissues. Especially, the adrenal medulla and circulating leukocytes seem to be potent inhibitors of lymphangiogenesis. We provide additional evidence for a role of esVEGFR-2 in NB. Thereby, high levels of esVEGFR-2 correlate with a more differentiated phenotype, and may inhibit tumour progression by inhibition of lymphangiogenesis.

In situ-RT-PCR and immunohistochemistry for the localisation of the mRNA of the alpha 3 chain of laminin and laminin-5 during human organogenesis

Laminin-5 is known to be an integral part of the hemidesmosome and therefore responsible for the integrity of the connection of the epithelium to the basement membrane. This is also an important mechanism during embryonic development, as documented by studies in mice. In an attempt to elucidate its implication for human development we localised the mRNA of the alpha3 chain of laminin with the help of in situ RT-PCR, and the laminin-5 protein immunohistochemically. We systematically investigated kidney, lung, skin and intestinal tissue of consecutive developmental stages during human embryogenesis. From gw 6.5 onwards, the mRNA of the alpha3 chain of laminin was found exclusively in the cytoplasm of epithelial cells of the developing kidney, lung, skin and intestine. Interestingly, in the skin and intestine from gw 8 onwards, the superficial cell layers also stained positive for the mRNA, while the protein was still only found in the dermal-epidermal and enteric basement membrane zones. In all developing organs investigated, the mRNA of the alpha3 chain of laminin is strictly of epithelial origin and the corresponding protein localised in the underlying basement membrane zones. Due to this discrepancy, we postulate a broader role for laminin-5 during human embryogenesis, for example, for epithelial cell development, beyond its involvement in hemidesmosome formation and cell adhesion.

Nidogen-1 and nidogen-2 are found in basement membranes during human embryonic development

The recently identified nidogen-2 is a matrix protein showing homology to the well-known basement membrane molecule nidogen-1. Nidogen-1 might well serve as a link between laminin-1 and collagen type IV and thus stabilise certain basement membranes in vivo and play a major role in embryogenesis. However, the exact tissue distribution of nidogen-1 and nidogen-2 during human embryogenesis is still unclear. As a first step towards the elucidation of their possible cell biological functions during human development, we compared the distribution of both nidogens during human organogenesis at the light microscope level. Nidogen-2 and nidogen-1 were found to be ubiquitous components of basement membrane zones underneath developing epithelia of most of the major organ systems. However, in the developing intestine and the pancreas anlage, only nidogen-1 was present in the epithelial basement membrane zones of all developmental stages investigated. Our data suggest that nidogen-2 and nidogen-1, as is known for mouse development, could well participate in cell biological functions during human development. These two proteins might well be able to fulfil identical functions during human organogenesis.