Effect of heme and heme oxygenase-1 on vascular endothelial growth factor synthesis and angiogenic potency of human keratinocytes

Background: Skin injury leads to the release of heme, a potent prooxidant which is degraded by heme oxygenase-1 (HO-1) to carbon monoxide, iron, and biliverdin, subsequently reduced to bilirubin. Recently the involvement of HO-1 in angiogenesis has been shown; however, the role of heme and HO-1 in wound healing angiogenesis has not been yet investigated. Results: Treatment of HaCaT keratinocytes with hemin (heme chloride) induced HO-1 expression and activity. The effect of heme on vascular endothelial growth factor (VEGF) synthesis is variable: induction is significant after a short, 6-h treatment with heme, while longer stimulation may attenuate its production. The involvement of HO-1 in VEGF synthesis was confirmed by inhibition of VEGF expression by SnPPIX, a blocker of HO activity and by attenuation of HO-1 mRNA expression with specific siRNA. Importantly, induction of HO-1 by hemin was able to overcome the inhibitory effect of high glucose on VEGF synthesis. Moreover, HO-1 expression was also induced in keratinocytes cultured in hypoxia, with concomitant augmentation of VEGF production, which was further potentiated by hemin stimulation. Accordingly, conditioned media from keratinocytes overexpressing HO-1 enhanced endothelial cell proliferation and augmented formation of capillaries in angiogenic assay in vitro. Conclusions: HO-1 is involved in hemin-induced VEGF expression in HaCaT and may play a role in hypoxic regulation of this protein. HO-1 overexpression may be beneficial in restoring the proper synthesis of VEGF disturbed in diabetic conditions

Atorvastatin affects several angiogenic mediators in human endothelial cells

The pleiotropic effects of statins, inhibitors of 3-hydroxy-3-methylglutaryl–coenzyme A (HMG-CoA) reductase, have been recently extended to the modulation of angiogenesis. Here, to get more insight into the statins action, the authors have investigated the effect of atorvastatin on the expression of several angiogenic and inflammatory genes in human umbilical endothelial cells (HUVECs). Atorvastatin was proangiogenic at the dose of 10 nM, and antiangiogenic at the concentrations of 1 to 10 μM. Moreover, these higher concentrations inhibited also the proliferation of HUVECs induced by vascular endothelial growth factor (VEGF). Lower doses of atorvastatin did not influence endothelial cell proliferation. Importantly, atorvastatin at the micromolar concentrations diminished the production of interleukin (IL)-8, a proinflammatory and proangiogenic chemokine, and inhibited the synthesis of urokinase plasminogen activator (uPA), a potent proinflammatory mediator. However, it decreased also the expression of plasminogen activator inhibitor-1 (PAI-1) and thrombospondin-1 (TSP-1), the inhibitors of angiogenesis. Atorvastatin stimulated the expression of angiopoietin (Ang)-2 and moderately enhanced the expression of endothelial nitric oxide synthase (eNOS), whereas heme oxygenase-1 (HO-1) was not significantly affected. In conclusion, the present findings points to other angiogenesis-related effects of atorvastatin, which may be of relevance to the beneficial influence of statins in cardiovascular system

Investigations on the impact of the introduction of the Aloe vera into the hydrogel matrix on cytotoxic and hydrophilic properties of these systems considered as potential wound dressings

In the paper, synthesis of chitosan-based hydrogels modified with Aloe vera juice is presented. The novelty of the research was a combination of hydrogel materials with properties beneficial in viewpoint of their use as modern wound dressings and Aloe vera juice supporting the wound healing process. Hydrogels have been obtained via UV radiation. The impact of the amount of the crosslinking agent as well as the introduction of the Aloe vera juice into the hydrogel matrix has been determined. Performed measurements involved analysis of the swelling ability, characteristics of the surface roughness, determining the release profile of Aloe vera and the contact angles of hydrogels. Furthermore, the analysis of the dehydration process of the polymer membrane, investigations on the cytotoxicity of hydrogels via MTT reduction assay and the neutral red uptake assay as well as the studies on the pro-inflammatory activity have also been performed. It was proved that the addition of Aloe vera juice improves the hydrophilic properties of the materials (e.g. contact angle changed from 82.5° to 73.0°). Next, the use of 25% more of the crosslinker resulted even in the increase of the contact angle by 86%. Modified hydrogels showed higher swelling properties even by 15% than unmodified materials. Furthermore, obtained hydrogels show an ability to release Aloe vera – after 5 h approx. 80% of this additive has been released in an acidic environment. Tested materials do not exhibit cytotoxic properties, the addition of Aloe vera results in an improvement of the viability of L929 murine fibroblasts and, importantly, these materials show lower pro-inflammatory activity than the positive control. Performed investigations allow to state that obtained materials show a great application potential

Self-Assembly Properties of Semiconducting Donor–Acceptor–Donor Bithienyl Derivatives of Tetrazine and ThiadiazoleEffect of the Electron Accepting Central Ring

Scanning tunneling microscopy was used to study the effect of the electron-accepting unit and the alkyl substituent’s position on the type and extent of 2D supramolecular organization of penta-ring donor–acceptor–donor (DAD) semiconductors, consisting of either tetrazine or thiadiazole central acceptor ring symmetrically attached to two bithienyl groups. Microscopic observations of monomolecular layers on HOPG of four alkyl derivatives of the studied adsorbates indicate significant differences in their 2D organizations. Ordered monolayers of thiadiazole derivatives are relatively loose and, independent of the position of alkyl substituents, characterized by large intermolecular separation of acceptor units in the adjacent molecules located in the face-to-face configuration. The 2D supramolecular architecture in both derivatives of thiadiazole is very sensitive to the alkyl substituent’s position. Significantly different behavior is observed for derivatives of tetrazine (which is a stronger electron acceptor). Stronger intermolecular DA interactions in these adsorbates generate an intermolecular shift in the monolayer, which is a dominant factor determining the 2D structural organization. As a consequence of this molecular arrangement, tetrazine groups (A segments) face thiophene rings (D segments) of the neighboring molecules. Monolayers of tetrazine derivatives are therefore much more densely packed and characterized by similar π-stacking of molecules independently of the position of alkyl substituents. Moreover, a comparative study of 3D supramolecular organization, deduced from the X-ray diffraction patterns, is also presented clearly confirming the polymorphism of the studied adsorbates