Heparan sulfate maintains adult midgut homeostasis in Drosophila

Tissue homeostasis is controlled by the differentiated progeny of residential progenitors (stem cells). Adult stem cells constantly adjust their proliferation/differentiation rates to respond to tissue damage and stresses. However, how differentiated cells maintain tissue homeostasis remains unclear. Here, we find that heparan sulfate (HS), a class of glycosaminoglycan (GAG) chains, protects differentiated cells from loss to maintain intestinal homeostasis. HS depletion in enterocytes (ECs) leads to intestinal homeostasis disruption, with accumulation of intestinal stem cell (ISC)‐like cells and mis‐differentiated progeny. HS‐deficient ECs are prone to cell death/stress and induced cytokine and epidermal growth factor (EGF) expression, which, in turn, promote ISC proliferation and differentiation. Interestingly, HS depletion in ECs results in the inactivation of decapentaplegic (Dpp) signaling. Moreover, ectopic Dpp signaling completely rescued the defects caused by HS depletion. Together, our data demonstrate that HS is required for Dpp signal activation in ECs, thereby protecting ECs from ablation to maintain midgut homeostasis. Our data shed light into the regulatory mechanisms of how differentiated cells contribute to tissue homeostasis maintenance.     

Reduced expression of CYLD promotes cell survival and inflammation in gefitinib‐treated NSCLC PC‐9 cells: Targeting CYLD may be beneficial for acquired resistance to gefitinib therapy

The application of tyrosine kinase inhibitors (TKIs) to the epidermal growth factor receptor (EGFR) has been proven to be highly effective for non‐small‐cell lung cancer (NSCLC). However, patients often evolve into acquired resistance. The secondary mutations in EGFR account for nearly half of the acquired resistance. While the remaining 50% of patients exhibit tolerance to EGFR‐TKIs with unclear mechanism(s). Cylindromatosis (CYLD), a deubiquitinase, functions as a tumor suppressor to regulate cell apoptosis, proliferation, and immune response, and so on. The role of CYLD in NSCLC EGFR‐TKI resistance remains elusive. Here, we found CYLD was upregulated in PC‐9 cells, whereas downregulated in PC‐9 acquired gefitinib‐resistant (PC‐9/GR) cells in response to the treatment of gefitinib, which is consistent with the results in the Gene Expression Omnibus database. Overexpression of CYLD promoted a more apoptotic death ratio in PC‐9/GR cells than that in PC‐9 cells. In addition, silencing the expression of CYLD resulted in an increase of the expression level of interleukin‐6, transforming growth factor‐β and tumor necrosis factor‐α, which may contribute to acquired resistance of PC‐9 cells to gefitinib. Taken together, our data in vitro demonstrate that PC‐9/GR cells downregulated CYLD expression, enhanced subsequent CYLD‐dependent antiapoptotic capacity and inflammatory response, which may provide a possible target for acquired gefitinib‐resistant treatment in NSCLC.     

A ROCK inhibitor promotes keratinocyte survival and paracrine secretion,enhancing establishment of primary human melanocytes and melanocyte–keratinocyte co‐cultures

Primary melanocytes isolated from skin and expanded in culture have been widely used for laboratory research and clinical applications. The conventional method to isolate primary melanocytes from skin usually requires about 3–4 weeks of culture for melanocytes to grow sufficiently to passage. Considering that melanocytes comprise only 3%–7% of epidermal cells in normal human skin, it would be extremely helpful to increase the isolation efficiency and shorten the initial culture time to quickly meet various application needs. Here, we report that adding Y‐27632, a Rho kinase inhibitor, into the initial culture medium for 2 days can dramatically increase the yield of melanocytes. We found that Y‐27632 can promote keratinocyte attachment and survival in the melanocyte culture system, resulting in not only better recovery, but also increased proliferation of melanocytes by a paracrine signaling pathway. More specifically, Y‐27632 significantly induced keratinocyte expression of stem cell factor, which played an important role in enhancing the growth of melanocytes. In summary, Y‐27632 could profoundly enhance the yield of primary melanocytes in the initial culture through paracrine effects on keratinocytes.     

The effect of intrauterine inflammation on mTOR signaling in mouse fetal brain

Fetuses exposed to an inflammatory environment are predisposed to long‐term adverse neurological outcomes. However, the mechanism by which intrauterine inflammation (IUI) is responsible for abnormal fetal brain development is not fully understood. The mechanistic target of rapamycin (mTOR) signaling pathway is closely associated with fetal brain development. We hypothesized that mTOR signaling might be involved in fetal brain injury and malformation when fetuses are exposed to the IUI environment. A well‐established IUI model was utilized by intrauterine injection of lipopolysaccharide (LPS) to explore the effect of IUI on mTOR signaling in mouse fetal brains. We found that microglia activation in LPS fetal brains was increased, as demonstrated by elevated Iba‐1 protein level and immunofluorescence density. LPS fetal brains also showed reduced neuronal cell counts, decreased cell proliferation demonstrated by low Ki67‐positive density, and elevated neuron apoptosis evidenced by high expression of cleaved Caspase 3. Furthermore, we found that mTOR signaling in LPS fetal brains was elevated at 2 hr after LPS treatment, declined at 6 hr and showed overall inhibition at 24 hr. In summary, our study revealed that LPS‐induced IUI leads to increased activation of microglia cells, neuronal damage, and dynamic alterations in mTOR signaling in the mouse fetal brain. Our findings indicate that abnormal changes in mTOR signaling may underlie the development of future neurological complications in offspring exposed to prenatal IUI.     

Discovery of small molecule antagonists of chemokine receptor CXCR6 that arrest tumor growth in SK-HEP-1 mouse xenografts as a model of hepatocellular carcinoma

The chemokine system plays an important role in mediating a proinflammatory microenvironment for tumor growth in hepatocellular carcinoma (HCC). The CXCR6 receptor and its natural ligand CXCL16 are expressed at high levels in HCC cell lines and tumor tissues and receptor expression correlates with increased neutrophils in these tissues contributing to poor prognosis in patients. Availability of pharmacologcal tools targeting the CXCR6/CXCL16 axis are needed to elucidate the mechanism whereby neutrophils are affected in the tumor environment. We report the discovery of a series of small molecules with an exo-[3.3.1]azabicyclononane core. Our lead compound 81 is a potent (EC₅₀ = 40 nM) and selective orally bioavailable small molecule antagonist of human CXCR6 receptor signaling that significantly decreases tumor growth in a 30-day mouse xenograft model of HCC.     

Light controls stamen elongation via cryptochromes,phytochromes and COP1 through HY5 and HYH

In Arabidopsis, stamen elongation, which ensures male fertility, is controlled by the auxin response factor ARF8, which regulates the expression of the auxin repressor IAA19. Here, we uncover a role for light in controlling stamen elongation. By an extensive genetic and molecular analysis we show that the repressor of light signaling COP1, through its targets HY5 and HYH, controls stamen elongation, and that HY5 – oppositely to ARF8 – directly represses the expression of IAA19 in stamens. In addition, we show that in closed flower buds, when light is shielded by sepals and petals, the blue light receptors CRY1/CRY2 repress stamen elongation. Coherently, at flower disclosure and in subsequent stages, stamen elongation is repressed by the red and far‐red light receptors PHYA/PHYB. In conclusion, different light qualities – sequentially perceived by specific photoreceptors – and the downstream COP1–HY5/HYH module finely tune auxin‐induced stamen elongation and thus male fertility.