Pyrene-phenylglycinol linked reversible ratiometric fluorescent chemosensor for the detection of aluminium in nanomolar range and its bio-imaging

Pyrene-phenylglycinol tangled ratiometric sensor (R)-1 was developed for the detection of Al³⁺ ion over other metal ions. Ratiometric behaviour of (R)-1 for Al³⁺ ion explained through monomer emission and excimer quenching leads to avoiding the π-π interactions of bis-pyrene rings. Pull-push to push-pull binding mechanism is successfully explained by DFT and sensing of Al³⁺-ions demonstrated in living cells. The LOD of (R)-1 for Al³⁺ downs to nanomolar concentrations which is lower than the allowed concentration of drinking water set by the (World Health Organization) WHO.

Fabrication of electrospun zein nanofibers for the sustained delivery of siRNA

In this study, zein nanofibers based siRNA delivery system has been attempted for the first time. Here, the amphiphilic property of zein and the size advantage of nanofibers have been brought together in developing an ideal delivery system for siRNA. The morphological analysis of the GAPDH-siRNA loaded zein nanofibers revealed the proper encapsulation of the siRNA in the polymeric matrix. The loading efficiency of this delivery system was found to be 58.57±2.4% (w/w). The agarose gel analysis revealed that the zein nanofibers preserved the integrity of siRNA for a longer period even at the room temperature. The in vitro release studies not only depicted the sustaining potential of the zein nanofibers but also ensured the release of sufficient quantity of siRNA required to induce the gene silencing effect. The amphiphilic property of zein supported the cell attachment and thereby facilitated the transfection of siRNA into the cells. qRT-PCR analysis confirmed the potential of the developed system in inducing the desired gene silencing effect. Thus, electrospun zein nanofibers have been successfully employed for the delivery of siRNA which has a great therapeutic potential.

A new platinum(ii) complex for bioimaging applications

A new Pt(ii) complex bearing terpyridine derivative exhibit specificity towards nuclear DNA. The staining ability has been explored in cell imaging as well as in gel electrophoresis an alternative to highly mutagenic ethidium bromide.

Changes in expression of VE-cadherin and MMPs in endothelial cells: Implications for angiogenesis

The mechanism of cell-cell contact dependent regulation of pericellular proteolysis in angiogenesis was examined by studying the expression of MMPs using isolated HUVECs in culture. Zymography, Immunoblot and RT-PCR analysis showed that the production and secretion of matrixmetalloproteinase-2 and matrixmetalloproteinase-9 by HUVECs in culture were high when they remain as individual cells and significantly decreased during later stages of culture when cells developed cell-cell contact and tubular network-like structure. As MMPs decreased there was significant upregulation of VE-cadherin in cells undergoing angiogenic transition. Investigations to understand the signaling pathways downstream of VE-cadherin showed a relatively high level of β-catenin in the nucleus of endothelial cells in culture during initial stages and decrease in its levels in the nucleus, associated with an increase in the cytosol during later stages of culture. The distribution of β-catenin was found to be regulated by Tyr/Ser phosphorylation status of this protein. Cell-cell contact dependent downregulation of MMPs during angiogenesis was also observed in experiments using proangiogenic substances which caused a rapid rate of downregulation of MMP-2 and MMP-9 and absence of downregulation of MMPs when treated with anti-angiogenic agents.

Imaging the cell wall of living single yeast cells using surface-enhanced Raman spectroscopy

The surface of a living yeast cell (Saccharomyces cerevisiae strain W303-1A) has been labeled with silver (Ag) nanoparticles that can form nanoaggregates which have been shown to have surface-enhanced Raman scattering (SERS) activity. The cell wall of a single living yeast cell has been imaged by use of a Raman microspectroscope. The SERS spectra measured from different Ag nanoaggregates were found to be different. This can be explained on the basis of detailed spectral interpretation. The SERS spectral response originates from mannoproteins which cover the outermost regions of the yeast cell wall. Analysis of SERS spectra from the cell wall and the extracted mannoproteins from the yeast has been performed for the clarification of variation in SERS spectra.

Modulation of cyclooxygenase in endothelial cells by fibronectin: relevance to angiogenesis

Cyclooxygenases (COX), which catalyze the formation of prostaglandins (PGs), have been implicated in angiogenesis. Adhesion of endothelial cells (ECs) to extracellular matrix (ECM) induces the expression of COX-2 and PG production. The present study was carried out to analyze the influence of the adhesive ECM protein, fibronectin (FN), in modulating COX expression and its implications to angiogenesis using in vitro cultures of human umbilical vein ECs. RT-PCR analysis showed that the level of COX-2 mRNA was significantly high while that of COX-1 decreased in ECs maintained on FN. On treatment with p38 MAPK inhibitor and anti-alpha(5)beta(1) integrin antibody, FN dependent effect on COX expression was not observed. Analysis by ELISA and immunoblotting confirmed FN-dependent upregulation of COX-2 protein. The ratio of PG E(2):PG D(2) was significantly high in cells maintained on FN and on treatment with p38 MAPK inhibitor, the relative level of PG D(2) increased and that of PG E(2) decreased. Concomitant with the modulation of COX-2 and changes in PGs, ECs maintained on FN showed angiogenic response in an alpha(5)beta(1) integrin/p38 MAPK dependent manner as evidenced by the expression of angiogenic markers, CD 31 and E-selectin. These results suggest a FN-alpha(5)beta(1)/FAK/p38 MAPK dependent upregulation of COX-2 causing a shift in the relative levels of PGs in HUVECs which contributes to the angiogenic effect of FN.

Modulation of expression of LDH isoenzymes in endothelial cells by laminin: implications for angiogenesis

Endothelial cell (EC) matrix interaction is critical in angiogenesis. Although matrix components can regulate the process of angiogenesis by acting as a reservoir of various cytokines, it is not clear if extracellular matrix (ECM) can modulate the production and activity of angiogenic cytokines. Investigations were therefore carried out to study the influence of the basement membrane (BM) protein, laminin (Ln) on the activity of vascular endothelial growth factor (VEGF), the major angiogenic cytokine, using isolated human umbilical vein ECs (HUVECs) in culture. Analysis of the biochemical markers of angiogenesis confirmed proangiogenic effect of Ln. The levels of VEGF protein and mRNA were not different in cells maintained on Ln, collagen I or polylysine substrata. Chorioallantoic membrane assay using VEGF isolated from cell extracts however revealed that Ln increased its angiogenic potency. Immunoblotting and HPLC analysis showed considerable reduction in poly adenosyl ribosylation of VEGF associated with a significant decrease in the levels of NAD+, in cells maintained on Ln substrata. Further, a shift in the isoenzymic pattern of LDH towards the B rich forms and an upregulation of LDH B gene were observed in cells maintained on Ln. Ln modulates expression of LDH gene through alpha(6)beta(4) integrin mediated downstream signaling involving p38 mitogen activated protein kinases (MAPK) pathway. It thus appears that Ln can affect aerobic metabolism of ECs by modulating the expression of LDH isoenzymes resulting in a decrease in the level of NAD+ that can cause a reduction in the poly adenosyl ribosylation of VEGF altering its angiogenic potency.

Modulation of angiogenic factors by ursolic acid

Investigations were carried out to understand the molecular basis of the effect of ursolic acid on angiogenesis by analysing its effects on the expression of modulators of angiogenesis by HUVECs in culture. Treatment with ursolic acid increased the expression of adhesion molecules such as E-selectin, CD-31 and I-CAM, upregulated angiogenic growth factors such as VEGF and FGF-2 and their receptors and caused increase in the ratio of PGE(2) to PGD(2). Reversal of the effect of ursolic acid by inhibition of PI3K-Akt pathway and increase in the level of phospho Akt suggest that the ursolic acid effect is mediated through PI3K-Akt pathway.

Opposing effects of curcuminoids on serum stimulated and unstimulated angiogenic response

Curcumin is known to be a potent wound healer. Despite this, studies on curcumin using certain model systems have shown it to be anti-angiogenic. Results of the present investigations suggest that curcumin causes opposing effects on angiogenesis in serum stimulated and unstimulated conditions. The evidence in support of this are: (a) in serum free conditions, curcumin promoted sprouting in rat aortic ring, increased vascular density in CAM and induced morphological changes indicative of angiogenic phenotype in HUVECs and rat aortic endothelial cells in culture, (b) increased the expression of biochemical markers of angiogenesis such as CD 31, E-selectin, VEGF and VEGFR-2 in HUVECs on treatment with curcumin, and (c) supplementation of curcumin along with serum caused decrease in CD 31 and E-selectin levels, downregulation of VEGF, angiopoietin-1 and VEGFR-2 and delayed formation of capillary network-like structure. Proangiogenic effect of the individual components of the natural curcumin differed and the presence of the three components in the natural mixture has a synergistic effect. Effect of curcuminoids in the absence of serum appears to depend on VEGF as (a) anti-VEGF antibody blocked the effect of curcuminoids (b) curcuminoids caused decrease in PAR modification of VEGF increasing its biological activity. Treatment with curcuminoids in serum-free conditions resulted in activation of PI3K-Akt pathway; but in serum-supplemented condition, curcuminoids caused inhibition of the MAPK pathways thereby inhibiting the expression of angiogenic phenotype. These results suggest that PI3K-Akt and MAPK pathways involved in the expression of angiogenic phenotype respond differently to the extracellular microenvironment.

Angiogenic response of endothelial cells to heparin-binding domain of fibronectin

Interaction of endothelial cells with cell-binding domain of fibronectin through integrin receptors is important in the process of angiogenesis. The present study was designed to examine the role of heparin-binding domain of fibronectin in angiogenesis using human umbilical vein endothelial cells. Attachment of endothelial cells in vitro to heparin-binding domain of fibronectin was inhibited by heparin. Chick chorioallantoic membrane assay revealed the proangiogenic nature of heparin-binding domain. Analysis by reverse transcription-polymerase chain reaction showed an increase in the expression of vascular endothelial growth factor and its receptor mRNA. Enzyme-linked immunosorbent assay showed a significant increase in the level of vascular endothelial growth factor secreted by cells maintained on heparin-binding domain. Treatment with calphostin C, an inhibitor of protein kinase C, decreased the expression of vascular endothelial growth factor receptor 2. Chick chorioallantoic membrane assay showed that the vascular endothelial growth factor secreted by cells maintained on heparin-binding domain was biologically more active, which appeared to be due to a decrease in its poly-adenosine diphosphate ribosylation. Binding assays showed that heparin-binding domain preferably binds unmodified vascular endothelial growth factor as compared to intact fibronectin. It is concluded that the heparin-binding domain of fibronectin by itself can promote angiogenesis in endothelial cells possibly by interaction with cell surface heparan sulphate proteoglycans involving protein kinase C dependent signaling and making available more active form of vascular endothelial growth factor to the cells.

Endothelial cell response to lactate: implication of PAR modification of VEGF

Angiogenesis, the process of formation of new blood vessels from pre-existing one, occurs in many physiological and pathological conditions, most of which are underlined by hypoxia and resultant accumulation of lactate. Although lactate is known to induce angiogenesis, the mechanism of its action on endothelial cells (ECs) is not known. The present study was designed to examine the response of ECs to lactate. Morphological analysis revealed that human umbilical vein endothelial cells (HUVECs) in culture respond to lactate by switching over to angiogenic phenotype concomitant with upregulation of vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 (VEGFR2) as determined by reverse transcription-PCR (RT-PCR). Apart from increase in the levels of VEGF protein as determined by ELISA, chorio allantoic membrane (CAM) assay using the cell extracts revealed that lactate also increased the angiogenic potency of VEGF. Isolated VEGF, when blotted and subsequently probed with anti-PAR antibody, revealed considerable reduction in poly-adenosyl ribosylation of VEGF associated with a significant decrease in the levels of NAD(+), in presence of lactate. Thus it appears that ECs respond to lactate by increasing the production of VEGF and modulating its angiogenic potency through poly-ADP ribosylation (PAR)-dependent mechanism and thereby switch over to angiogenic phenotype.

Temporal relationship between MMP production and angiogenic process in HUVECs

Alterations in both cell-cell and cell-matrix interactions are associated with the activation of endothelial cells that initiate angiogenesis. Cell-matrix interactions are affected by changes in both cell surface receptors for matrix proteins and the composition of ECM. One of the molecular mechanisms involved in changes in these components is the action of neutral proteinases, particularly matrix metalloproteinases. To understand the involvement of MMPs in angiogenic processes, the in vitro model of human umbilical vein endothelial cells in culture was used. Zymography and ELISA showed that, as cell-cell contact and network-like structures were formed, there was down regulation of MMP-2 and MMP-9 associated with high levels of their endogenous inhibitors TIMP-1 and TIMP-2. On treatment with aspirin, which inhibited the cell-cell contact and network-like structure formation, there was no down regulation of MMPs and cells continued to produce MMP-2 and MMP-9. These results indicate a temporal relationship between MMP-2 and MMP-9 production by endothelial cells and the onset of angiogenic event.