Attenuated migration by green tea extract (−)-epigallocatechin gallate (EGCG): involvement of 67 kDa laminin receptor internalization in macrophagic cells

Non-integrin laminin receptor (LamR) plays a role in axonal outgrowth from chicken DRG via modulating the Akt and Erk signaling

37/67 kDa laminin receptor (LamR)/ribosomal protein SA exhibits dual function as both a ribosomal protein and cell surface receptor for laminin. LamR influences critical cellular processes such as invasion, adhesion, and migration when acting as a receptor. Despite the acknowledged importance of LamR/67LR in various cellular processes, its contribution to the peripheral nervous system development is obscure. Thus, this study investigated the biological activity of LamR in peripheral axonal outgrowth in the presence of laminin-1 or Ile-Lys-Val-Ala-Val (IKVAV) peptide, whose important role in dorsal root ganglia (DRG) axonal outgrowth we recently showed. Unexpectedly, we did not observe LamR on the surface of DRG cells or in a conditioned medium, suggesting its intracellular action in the negative regulation of DRG axonal outgrowth. Using C-terminus LamR-targeting IgG, we demonstrated the role of LamR in that process, which is independent of the presence of Schwann cell precursors (SCPs) and is mediated by extracellular signal-regulated kinase (Erk) and Protein kinase B (Akt1/2/3) signaling pathways. Additionally, we show that the action of LamR towards laminin-1-dependent axonal outgrowth is unmasked only when the activity of integrin β1 is perturbed. We believe that modulation of LamR activity provides the basis for its use for inhibiting axon growth as a potential therapeutic agent for regulating abnormal or excessive neurite growth during neurodevelopmental diseases or pathological nerve regeneration.

The roles of epigallocatechin gallate in the tumor microenvironment, metabolic reprogramming, and immunotherapy

Cancer, a disease that modern medicine has not fully understood and conquered, with its high incidence and mortality, deprives countless patients of health and even life. According to global cancer statistics, there were an estimated 19.3 million new cancer cases and nearly 10 million cancer deaths in 2020, with the age-standardized incidence and mortality rates of 201.0 and 100.7 per 100,000, respectively. Although remarkable advancements have been made in therapeutic strategies recently, the overall prognosis of cancer patients remains not optimistic. Consequently, there are still many severe challenges to be faced and difficult problems to be solved in cancer therapy today. Epigallocatechin gallate (EGCG), a natural polyphenol extracted from tea leaves, has received much attention for its antitumor effects. Accumulating investigations have confirmed that EGCG can inhibit tumorigenesis and progression by triggering apoptosis, suppressing proliferation, invasion, and migration, altering tumor epigenetic modification, and overcoming chemotherapy resistance. Nevertheless, its regulatory roles and biomolecular mechanisms in the immune microenvironment, metabolic microenvironment, and immunotherapy remain obscure. In this article, we summarized the most recent updates about the effects of EGCG on tumor microenvironment (TME), metabolic reprogramming, and anti-cancer immunotherapy. The results demonstrated EGCG can promote the anti-cancer immune response of cytotoxic lymphocytes and dendritic cells (DCs), attenuate the immunosuppression of myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs), and inhibit the tumor-promoting functions of tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), and various stromal cells including cancer-associated fibroblasts (CAFs), endothelial cells (ECs), stellate cells, and mesenchymal stem/stromal cells (MSCs). Additionally, EGCG can suppress multiple metabolic reprogramming pathways, including glucose uptake, aerobic glycolysis, glutamine metabolism, fatty acid anabolism, and nucleotide synthesis. Finally, EGCG, as an immunomodulator and immune checkpoint blockade, can enhance immunotherapeutic efficacy and may be a promising candidate for antitumor immunotherapy. In conclusion, EGCG plays versatile regulatory roles in TME and metabolic reprogramming, which provides novel insights and combined therapeutic strategies for cancer immunotherapy.

Targeting beta-catenin signaling for prevention of colorectal cancer - Nutraceutical, drug, and dietary options

Progressive up-regulation of β-catenin signaling is very common in the transformation of colorectal epithelium to colorectal cancer (CRC). Practical measures for opposing such signaling hence have potential for preventing or slowing such transformation. cAMP/PKA activity in colon epithelium, as stimulated by COX-2-generated prostaglandins and β2-adrenergic signaling, boosts β-catenin activity, whereas cGMP/PKG signaling has the opposite effect. Bacterial generation of short-chain fatty acids (as supported by unrefined high-carbohydrate diets, berberine, and probiotics), dietary calcium, daily aspirin, antioxidants opposing cox-2 induction, and nicotine avoidance, can suppress cAMP production in colonic epithelium, whereas cGMP can be boosted via linaclotides, PDE5 inhibitors such as sildenafil or icariin, and likely high-dose biotin. Selective activation of estrogen receptor-β by soy isoflavones, support of adequate vitamin D receptor activity with UV exposure or supplemental vitamin D, and inhibition of CK2 activity with flavanols such as quercetin, can also oppose β-catenin signaling in colorectal epithelium. Secondary bile acids, the colonic production of which can be diminished by low-fat diets and berberine, can up-regulate β-catenin activity by down-regulating farnesoid X receptor expression. Stimulation of PI3K/Akt via insulin, IGF-I, TLR4, and EGFR receptors boosts β-catenin levels via inhibition of glycogen synthase-3β; plant-based diets can down-regulate insulin and IGF-I levels, exercise training and leanness can keep insulin low, anthocyanins and their key metabolite ferulic acid have potential for opposing TLR4 signaling, and silibinin is a direct antagonist for EGFR. Partially hydrolyzed phytate can oppose growth factor-mediated down-regulation of β-catenin by inhibiting Akt activation. Multifactorial strategies for safely opposing β-catenin signaling can be complemented with measures that diminish colonic mutagenesis and DNA hypomethylation - such as avoidance of heme-rich meat and charred or processed meats, consumption of phase II-inductive foods and nutraceuticals (e.g., Crucifera), and assurance of adequate folate status.

Nutraceutical strategies for alleviation of UVB phototoxicity

Ultraviolet B exposure to keratinocytes promotes carcinogenesis by inducing pyrimidine dimer lesions in DNA, suppressing the nucleotide excision repair mechanism required to fix them, inhibiting the apoptosis required for the elimination of initiated cells, and driving cellular proliferation. Certain nutraceuticals - most prominently spirulina, soy isoflavones, long-chain omega-3 fatty acids, the green tea catechin epigallocatechin gallate (EGCG) and Polypodium leucotomos extract - have been shown to oppose photocarcinogenesis, as well as sunburn and photoaging, in UVB-exposed hairless mice. It is proposed that spirulina provides protection in this regard via phycocyanobilin-mediated inhibition of Nox1-dependent NADPH oxidase; that soy isoflavones do so by opposing NF-κB transcriptional activity via oestrogen receptor-beta; that the benefit of eicosapentaenoic acid reflects decreased production of prostaglandin E2; and that EGCG counters UVB-mediated phototoxicity via inhibition of the epidermal growth factor receptor. The prospects for practical nutraceutical down-regulation of photocarcinogenesis, sunburn, and photoaging appear favourable.

Epigallocatechin gallate regulates inflammatory responses and new bone formation through Wnt/β-Catenin/COX-2 pathway in spondyloarthritis

OBJECTIVE

Spondyloarthritis (SpA) is mainly characterized by bone erosion, new bone formation, inflammation and potential disability. Epigallocatechin gallate (EGCG) has been proved to be closely related with the regulation of inflammation and bone metabolism. However, whether EGCG could improve SpA remains unclear.

METHODS

SpA animal model was established using proteoglycan. Cell proliferation were measured by CCK-8 assay. The mRNA expression levels of genes were detected using qRT-PCR, protein levels were assessed via western blotting and immunohistochemistry. ELISA assay was performed to examined the inflammatory cytokine release. Lesions in spine cartilage tissues were observed using hematoxylin-eosin (HE) and Safranin O staining. Alkaline phosphatase (ALP) assay and Alizarin Red S staining was used to investigate osteoblast mineralization.

RESULTS

We found that EGCG could inhibit inflammation and new bone formation in SpA mice. Besides, inflammatory factor expression and osteogenic differentiation in osteoblasts isolated from SpA mice were also decreased by EGCG. Further, EGCG treatment suppressed the activation of Wnt/β-Catenin/COX-2 pathway and the activator of this pathway partially reversed the effects of EGCG on inflammation and osteoblast differentiation.

CONCLUSIONS

EGCG repressed inflammatory responses and new bone formation, and further improved SpA through Wnt/β-Catenin/COX-2 pathway. Our findings may provide a new thought for the prevention and treatment of SpA.

Green tea catechins inhibit microglial activation which prevents the development of neurological disorders

The over-activated microglial cells induce neuroinflammation which has the main role in neurological disorders. The over-activated microglia can disturb neuronal function by releasing inflammatory mediators leading to neuronal dysfunctions and death. Thus, inhibition of over-activated microglia may be an effective therapeutic approach for modulating neuroinflammation. Experimental studies have indicated anti-neuroinflammatory effects of flavonoids such as green tea catechins. The current research was aimed to review the effect of green tea catechins in inhibiting microglial cells, inflammatory cascades, and subsequent neurological diseases.

Laminin-1 induces endocytosis of 67KDa laminin receptor and protects Neuroscreen-1 cells against death induced by serum withdrawal

Although the function of laminin in the basement membrane is known, the function of soluble "neuronal" laminin is unknown. Since laminin is neuroprotective, we determined whether the soluble laminin-1 induces signaling for neuroprotection via its 67KDa laminin-1 receptor (67LR). Treatment of Neuroscreen-1 (NS-1) cells with laminin-1 or YIGSR peptide, which corresponds to a sequence in laminin-1 β1 chain that binds to 67LR, induced a decrease in the cell-surface expression of 67LR and caused its internalization. Furthermore, intracellular cAMP-elevating agents, dibutyryl-cAMP, forskolin, and rolipram, also induced this internalization. Both soluble laminin-1 and YIGSR induced a sustained elevation of intracellular cAMP under defined conditions, suggesting a causal role of cAMP in the endocytosis of 67LR. This endocytosis was not observed in cells deficient in protein kinase A (PKA) nor in cells treated with either SQ 22536, an inhibitor for adenylyl cyclase, or ESI-09, an inhibitor for the exchange protein directly activated by cAMP (Epac). In addition, when internalization occurred in NS-1 cells, 67LR and adenylyl cyclase were localized in early endosomes. Under conditions in which endocytosis had occurred, both laminin-1 and YIGSR protected NS-1 cells from cell death induced by serum withdrawal. However, under conditions in which endocytosis did not occur, neither laminin-1 nor YIGSR protected these cells. Conceivably, the binding of laminin-1 to 67LR causes initial signaling through PKA and Epac, which causes the internalization of 67LR, along with signaling enzymes, such as adenylyl cyclase, into early endosomes. This causes sustained signaling for protection against cell death induced by serum withdrawal.

Pigment epithelium-derived factor promotes tumor metastasis through an interaction with laminin receptor in hepatocellular carcinomas

Pigment epithelium-derived factor (PEDF) has complex functions in tumor metastasis, but little is known about the roles of PEDF and its receptors in hepatocellular carcinoma (HCC). Here we found that high expression of PEDF is associated with shorter overall survival in HCC patients. Forced expression of PEDF enhanced HCC cell aggressive behavior in vitro and in vivo, whereas silencing PEDF expression reduced migration and invasion. Furthermore, PEDF expression led to changes in cell morphology and the expression of epithelial-mesenchymal transition (EMT)-related markers via ERK1/2 signaling pathway, including the upregulation of N-cadherin and slug, and the downregulation of E-cadherin in HCC cells. Our results further showed that PEDF could interact with laminin receptor (LR) and LR knockdown attenuated PEDF-induced migration, invasion and the change of EMT-related markers. More importantly, in clinical HCC specimens, we found that PEDF expression was correlated with subcellular localization of LR, and that high expression of PEDF and positive expression of LR predicted a poor prognosis. In conclusion, our results demonstrate a novel functional role of PEDF/LR axis in driving metastasis through ERK1/2-mediated EMT in HCC and provided a promising prognostic marker in HCC.

Analysis of the effect of the active compound of green tea (EGCG) on the proliferation of peripheral blood mononuclear cells

Background

Cancer immunotherapy requires proper manipulation of the immune system, lymphocytes in particular, in order to identify and destroy the cancer cells as non-self. In this study we investigated the effect of the flavonoid present in green tea, namely epigallocatechin-3-gallate (EGCG), on the proliferation of, and IFN-γ production by, peripheral blood mononuclear cells (PBMC) from breast cancer patients stimulated with a mitogen, anti-CD3 and the common breast cancer peptides Her-2/neu, and p53.

Methods

Blood samples were collected from 25 patients with breast cancer at the Kuwait Cancer Control Centre (KCCC). The patients were newly diagnosed, and had not undergone any treatment or surgery at the time of sample collection. The control group consisted of 25 healthy women age-matched (±5 years) to the patients. PBMC were isolated from the patients and controls, and were cultured separately with the mitogen PHA, anti-CD3 antibodies, and Her-2/neu and p53 in the presence or absence of standardized doses of EGCG. The degree of proliferation and interferon-γ [IFN-γ) release were then analyzed.

Results

EGCG significantly suppressed the proliferation of PBMC in response to stimulation separately with (i) the mitogen, (ii) anti-CD3, and (iii) the cancer antigen peptides. IFN-γ production was also significantly suppressed by EGCG in vitro.

Conclusions

EGCG appears to have an immunosuppressive effect on the proliferation of PBMC, indicating that EGCG is worth exploring for immunomodulatory effects in autoimmune diseases and tissue transplantation.