High-dose alpha-tocopherol therapy does not affect HDL subfractions in patients with coronary artery disease on statin therapy

BACKGROUND: Subfractions of HDL, particularly large HDL (HDL2), are inversely correlated with the severity of coronary artery disease (CAD). alpha-Tocopherol (AT) is the main lipid-soluble antioxidant in plasma. Results of a previous small study (n = 44) suggested that either a combination of an antioxidant cocktail [800 IU/day 2R,4'R,8'R-(RRR)-AT plus 1 g vitamin C, 25 mg beta-carotene, and 100 microg selenium] or individual antioxidant vitamins combined with simvastatin-niacin (S-N) therapy attenuated the protective increase in HDL2 seen with S-N alone. Few data are available on the effect of AT therapy alone on HDL subfractions, which we addressed in this study. METHODS: In a prospective placebo-controlled study, we randomized 127 patients with stable CAD to receive high-dose RRR-AT (1200 IU/day for 2 years) or placebo. HDL subfractions (small, medium, and large HDL particles) were analyzed by nuclear magnetic resonance spectroscopy. RESULTS: AT concentrations significantly increased in the AT arm but not with placebo. No differences were noted between AT and placebo groups in concentrations of total cholesterol, triglyceride, LDL-cholesterol, or HDL-cholesterol. AT therapy did not affect total, small, medium, or large HDL particles compared with baseline or placebo. Furthermore, serum apolipoprotein A1 concentrations did not change after 2 years AT therapy as compared with baseline. CONCLUSIONS: High-dose AT therapy administered for a 2-year period does not negatively affect either HDL subfractions or apolipoprotein A1 in patients with CAD on statin therapy. Thus the negative interaction previously proposed between antioxidant cocktail and statin therapy cannot be attributed to AT.     

Efficacy of grape seed proanthocyanidins on serum and heart tissue lipids in rats subjected to isoproterenol-induced myocardial injury

The present study was aimed to evaluate the preventive role of grape seed proanthocyanidins (GSPs) on serum and tissue lipid enzymes in isoproterenol (ISO)-induced myocardial injury in male Wistar albino rats. GSP was administered orally to rats (150-180 g) in three different doses, by gastric gavage (50, 100 and 150 mg/kg GSP), 6 days a week for 5 weeks. At the end of this period, all the rats, except the normal untreated rats that served as the control group, were administered ISO, 85 mg/kg subcutaneously, for 2 consecutive days to induce myocardial injury. After 48 h, rats (n=6 per group) were anesthetized with anesthetic ether, sacrificed and the levels of biochemical observations of the serum and heart tissues were performed. Biochemical assessment of myocardial injury was done by measuring the activities of serum thiobarbituric acid reactive substances and plasma lactate, which were significantly elevated in the rats administered with ISO. Further, our results suggest that prior administration of GSPs significantly maintained the cholesterol, phospholipids, triglycerides, and free fatty acids levels in serum and heart tissue of the ISO-induced myocardial injury in rats. The experiments conclude that GSPs possess cardioprotective and hypolipidemic effect on the treatment of ISO-induced myocardial injury.     

Protective role of Hemidesmus indicus R. Br. root extract against Salmonella typhimurium-induced cytotoxicity in Int 407 cell line

The present investigation deals with the effect of the chloroform fraction composed of sterols and fatty acids isolated from Hemidesmus indicus root extract (CHI) on Salmonella enterica serovar Typhimurium (S. typhimurium)-induced cytotoxicity in a human intestinal epithelial cell line (Int 407). The optimum dose was fixed as 100 microg/mL for CHI against S. typhimurium, which was quite safe for Int 407 cells as the CD(50) concentration (50% cell death) of CHI was determined to be 500 microg/mL in the Int 407 cell line. CHI-treated S. typhimurium were 10-fold less cytotoxic and 40% less adherent to host cells than wild-type. Treatment of CHI significantly abrogated the invasion ability to 10- to 15-fold in S. typhimurium. The cells infected with CHI-treated S. typhimurium had a comparable viability to uninfected cells in the epithelial cell detachment assay. Immunofluorescence showed the CHI-treated bacteria were unhealthy and shrunken rods in comparison with the wild-type bacteria; those were firmly attached and invaded to deceased and hypertrophoid Int 407 cells. Transmission electron micrographs of Int 407 cells infected with wild bacteria showed a coat of adherent and invaded bacteria completely occupying the cytoplasm with characteristic Salmonella-containing vacuoles (SCV). Both necrotic and apoptotic type of cell death were observed in cells infected with wild-type bacteria, whereas most of the cells infected with treated bacteria were normal in morphology and a few had invaded bacteria, but the typical proliferated SCV was not observed in cells infected with CHI-treated S. typhimurium. In summary, the sterols and fatty acids present in CHI may be capable of taming S. typhimurium by suppressing its cytotoxic activity in an intestinal epithelial cell line.     

Increased toll-like receptor (TLR) 2 and TLR4 expression in monocytes from patients with type 1 diabetes: further evidence of a proinflammatory state

CONTEXT: Type 1 diabetes (T1DM) is associated with increased cardiovascular mortality. It is a pro-inflammatory state as evidenced by increased circulating biomarkers and monocyte activity. The toll-like receptors (TLRs) are pattern recognition receptors, expressed abundantly on monocytes. TLR2 and TLR4 are important in atherosclerosis. However, there is a paucity of data examining TLR2 and TLR4 expression in T1DM and examining its contribution to the proinflammatory state. OBJECTIVE: Thus, we examined TLR2 and TLR4 expression in monocytes from T1DM patients compared with controls (n = 31 per group). SETTING: The study was performed at the University of California Davis Medical Center. PATIENTS: Healthy controls (n = 31) and T1DM patients (n = 31) were included in the study. RESULTS: TLR2 and TLR4 surface expression and mRNA were significantly increased in T1DM monocytes compared with controls. Downstream targets of TLR, nuclear factor kappaB, myeloid differentiation factor 88, Trif, and phosphorylated IL-1 receptor-associated kinase were significantly up-regulated in T1DM. Finally, the release of IL-1beta and TNF-alpha was significantly increased in monocytes from T1DM compared with controls and correlated with TLR2 and TLR4 expression (P < 0.005). In addition, TLR2 and TLR4 expression was significantly correlated to glycosylated hemoglobin, carboxymethyllysine, and nuclear factor kappaB (P < 0.02). CONCLUSION: Thus, we make the novel observation that TLR2 and TLR4 expression and signaling are increased in T1DM and contribute to the proinflammatory state.     

One-step solution synthesis of a two-dimensional semiconducting covalent organometallic nanosheet via the condensation of boronic acid

In this work, a 2D covalent organometallic nanosheet (COMS) was designed and successfully synthesized through the one-step conjunction of a terpyridine–metal–terpyridine (TMT) sandwich coordinate motif with borate ester covalent heterocyclic (B₃O₃) linkage via the condensation of boronic acid. The obtained 2D COMS with a cobalt coordination center (2D COMS-Co) showed promising p-type semiconducting properties.

A 2D covalent organometallic nanosheet (COMS-Co) was synthesized through the one-step conjunction of sandwich coordinate motif with covalent heterocyclic linkage via the condensation of boronic acid, and it showed promising semiconducting properties.

Two-dimensional (2D) metal–organic frameworks (MOFs) obtained by using the strong bonding effects between metal ions and organic molecule species have aroused great interest;^1–8 these include coordination nanosheets, which are a class of 2D materials featuring metal complex motifs.^9–12 Covalent bonds are considered to be an effective way to fabricate covalent organic frameworks (COFs) such as COF-1, which is mainly constructed by a phenyl ring and borate ester to form covalent heterocyclic (B₃O₃) linkage.^13–15 Based on the synergistic effects of metal coordination and covalent interactions, Jiang and co-workers demonstrated the important role of central metals in controlling π-electronic functions through Mpc-COF.¹⁶ Nevertheless, the coordination bond forms spontaneously within the ring of the porphyrin heterocycle and not as the linkage between organic components. In addition, the connections made between metal ions and ligand motifs cannot facilitate the proper tuning of the physicochemical properties of the structure.¹⁷ Combining the covalent and coordinate features may provide an opportunity to design new 2D materials and thus, the synergetic enhancement in many unique properties can be achieved. As far as we know, the fabrication of 2D semiconducting materials that combine the covalent heterocyclic linkage and coordinate linkage has not been reported. Therefore, it is a pressing need to construct a functional 2D organic framework through a one-step synthesis strategy, which would be a more attractive approach.Herein, we first proposed an efficient one-step strategy to synthesize a 2D material by the synergy of covalent and organometallic interactions; it was named as a covalent organometallic nanosheet (2D COMS-M, M = cobalt (Co)). The as-proposed 2D COMS-Co was constructed by linking the borate ester covalent heterocyclic (B₃O₃) structure and terpyridine (tpy) metal coordination motif (TMT) (Fig. 1).Open in a separate windowFig. 1(a) Synthesis route of the semiconducting 2D COMS. (b) Design principles of COMS via the condensation of boronic acid. (c) The calculated cross-sectional view of 2D COMS-Co.In order to explore the extended construction of 2D COMS, the self-condensation ligand 4-phenylborate-2,2′; 6′,2′′-terpyridine (L¹) integrated with CoCl₂ as the Co²⁺ carrier was employed through an anhydrous and oxygen-free hydrothermal reaction at 120 °C under argon, and the typical synthesis process is depicted in Fig. 1a (for details, please see ESI^†). Starting from the condensation reaction of boronic acid (Fig. 1b), H₂O could be generated and played a key role in dissolving CoCl₂ and further releasing Co²⁺ ions (CoCl₂ is practically insoluble in mesitylene and dioxane). This was followed by coordination between the terpyridine motifs and the released Co²⁺ ions to obtain 2D COMS. This novel strategy could achieve crystalline 2D materials by self-controlling the release of Co²⁺ through the one-step condensation reaction of boronic acid. The calculated cross-sectional view of 2D COMS-Co indicates that the thickness of the monolayer 2D COMS-Co is 0.69 nm (Fig. 1c). The dual synergistic connecting effects of covalence and coordination in 2D COMS-Co provided nanosheet-like morphology with significant improvement in the semiconducting performance. The hole mobility of the 2D COMS-Co-based FET device could reach to 5.7 × 10⁻⁵ cm² V⁻¹ s⁻¹ with an ON–OFF ratio of 221, which demonstrated the potential application of 2D COMS-Co in semiconducting devices.The scanning electron microscopy (SEM) image (Fig. 2a) reveals that 2D COMS-Co has a uniform micron-sized nanosheet-like structure. Furthermore, the transmission electron microscopy (TEM) image indicates that the as-synthesized 2D COMS-Co consists of few multi-layers. Fig. 2c shows an enlarged image of the selected area visualized with high-resolution TEM (HRTEM), where the section enclosed by white lines depicts lattice fringes. Moreover, the selected area electron diffraction (SAED, inset of Fig. 2c) image shows a circular ring pattern that reveals the well-defined crystalline structure of 2D COMS-Co; these results are in agreement with our X-ray diffraction data (Fig. S2, ESI^†). Most interestingly, the atomic force microscopy (AFM) image (Fig. 2d) clearly demonstrates that the selected thickness of 2D COMS-Co is 2.07 nm, and the resultant thickness is three times less than the calculated value of 0.69 nm (Fig. 1c), indicating its uniform three-layer stacked structure. The above results collectively provide strong evidence of typical 2D features for COMS-Co. Moreover, the high-angle annular dark-field (HAADF) image and the scanning transmission electron microscopy (STEM) elemental mapping further revealed that the C (red), B (cyan), N (green), O (blue) and Co (pink) elements are homogeneously distributed on the selected area of 2D COMS-Co (Fig. 2e–k). The electronic structure of 2D COMS-Co was further characterized by four-probe scanning tunnel microscopy (STM) (please see details in ESI^†). The high-resolution STM imaging revealed that the 2D COMS-Co flake has a layered flake structure with uniformly distributed hexagonal hole morphology and the resultant holes have a diameter of 4.72 nm (Fig. 2l); this observation is in accordance with the proposed structure of 2D COMS-Co (Fig. S8, ESI^†).Open in a separate windowFig. 2Morphological characterization of 2D COMS-Co. (a) SEM image of powder. (b) TEM image. (c) HRTEM image (d) AFM image. (e) HAADF image. (f–k) STEM elemental mapping. (l) STM image.Due to the covalence and coordination effects, the absorption peak of 2D COMS-Co obtained from the UV-vis measurements (Fig. 3a) is red-shifted in comparison to that for ligand L¹, and the optical band gap is calculated to be 1.85 eV. Furthermore, density functional theory (DFT) calculations revealed that the highest occupied molecular orbital (HOMO) of 2D COMS-Co was dominated by the π orbital of the B₃O₃ linkage and the phenyl ring, whereas the π* orbital of TMT was responsible for the lowest unoccupied molecular orbital (LUMO). Additionally, the calculated electronic band gap of 2D COMS-Co was 1.89 eV, which was in accordance with the optical band gap, confirming the successful synthesis of 2D COMS-Co. Fig. 3b displays the X-ray photoelectron spectroscopy (XPS) spectrum of 2D COMS-Co, in which the appearance of the binding energy peak at 192.2 eV is significantly different from that for L¹ (191.1 eV), which can be ascribed to the –C–B–O₂ structure.^18,19 Compared to the observation for L¹, the N 1s peak for 2D COMS-Co shifted to a higher binding energy value (399.2 eV for COMS-Co and 397.5 eV for L¹). The skewing of the peaks toward higher binding energy was induced by the contribution of N atoms in terpyridine to the metal center. Therefore, the XPS results clearly provide evidence of the existence of both covalent and coordination effects in the as-prepared 2D COMS-Co. The Fourier transform infrared (FT-IR) spectra in Fig. 3c show that the –B(OH)₂ bands (around 3500 cm⁻¹) of the ligand L¹ are significantly attenuated compared to that observed for 2D COMS-Co. In addition, the B–O stretching vibrations at 1351 cm⁻¹ can be observed for 2D COMS-Co but not for L¹.^13,20–22 Thus, the above results show that the expected B₃O₃ rings for 2D COMS-Co have indeed been formed. Notably, the nitrogen adsorption–desorption isotherms reveal that the Brunauer–Emmett–Teller (BET) specific surface area of 2D COMS-Co is as high as 598 m² g⁻¹ (Fig. 3d); it surpasses those of other layered materials, including the reported graphene oxide paper (10 m² g⁻¹), clays (10 to 100 m² g⁻¹), and pillared clays (50 to 300 m² g⁻¹), and is in the range of the values of the most porous zeolites and many porous carbons.^13,23 This drastic enhancement can be assigned to the uniform porous structure of the as-synthesized 2D COMS-Co.Open in a separate windowFig. 3(a) UV-vis spectra of L¹ and 2D COMS-Co (left), electron distribution on HOMO/LUMO and the orbital energy gap (right). (b) XPS B 1s and N 1s spectra of L¹ and 2D COMS-Co. (c) FT-IR spectra of L¹ and 2D COMS-Co. (d) N₂ adsorption and desorption isotherms of 2D COMS-Co (inset: stacking porous view).The above results show that the 2D COMS-Co units arranged in periodic strips can provide conducting pathways for charge carrier transport through TMT and central cobalt ions. 2D COMS-Co was employed to function as the active semiconducting channel in a field-effect transistor (FET) device. As shown in Fig. 4a, the individual 2D COMS-Co sample is deposited on an Si wafer as the semiconducting layer to construct the FET device. The 2D COMS-Co-based FET device delivered hole mobility of 5.7 × 10⁻⁵ cm² V⁻¹ S⁻¹ and an ON/OFF ratio of 221, which were comparable with those of previously reported 2D MOFs (Table S1^†). Therefore, these results collectively demonstrate the potential application of 2D COMS-Co in semiconducting devices.Open in a separate windowFig. 4(a) Schematic of the FET device employing 2D COMS-Co as the semiconducting layer. (b) Transfer curve of the 2D COMS-Co-based FET device with the inset showing an optical and model diagram of the device; V_G is the gate-source voltage and I_D is the drain current.In summary, a novel two-dimensional covalent organometallic nanosheet (COMS) was designed and successfully synthesized through the strategy of one-step conjunction of a TMT sandwich coordinate motif with B₃O₃ linkage. This facile strategy could achieve crystalline 2D COMS-Co by self-controlling the release of Co²⁺ through a one-step condensation reaction of boronic acid. The systematic characterization demonstrated the successful preparation of porous and crystalline 2D COMS-Co. Particularly, the as-prepared 2D COMS-Co-based FET device presented hole mobility of 5.7 × 10⁻⁵ cm² V⁻¹ S⁻¹ and an ON/OFF ratio of 221, which demonstrated the potential application of 2D COMS-Co in semiconducting devices. Therefore, we envision that this work will open a new avenue for the synthesis of two-dimensional semiconducting covalent organometallic materials by using covalence and coordination dual synergistic connection effects via a one-step facile strategy.     

C-reactive protein decreases endothelial nitric oxide synthase activity via uncoupling

C-reactive protein (CRP), a cardiovascular risk marker, induces endothelial dysfunction. We have previously shown that CRP decreases endothelial nitric oxide synthase (eNOS) expression and bioactivity in human aortic endothelial cells (HAECs). In this study, we examined the mechanisms by which CRP decreases eNOS activity in HAECs. To this end, we explored different strategies such as availability of tetrahydrobiopterin (BH4)-a critical cofactor for eNOS, superoxide (O(2)(-)) production resulting in uncoupling of eNOS and phosphorylation/dephosphorylation of eNOS. CRP treatment significantly decreased levels of BH4 thereby promoting eNOS uncoupling. Pretreatment with sepiapterin, a BH4 precursor, prevented CRP-mediated effects on BH(4) levels, superoxide production as well as eNOS activity. The gene expression and enzymatic activity of GTPCH1, the first enzyme in the de novo biosynthesis of BH(4), were significantly inhibited by CRP. Importantly, GTPCH1 is known to be regulated by cAMP-mediated pathway. In the present study, CRP-mediated inhibition of GTPCH1 activity was reversed by pretreatment with cAMP analogues. Furthermore, CRP-induced O(2)(-) production was reversed by pharmacologic inhibition and siRNAs to p47 phox and p22 phox. Additionally, CRP treatment significantly decreased the eNOS dimer: monomer ratio confirming CRP-mediated eNOS uncoupling. The pretreatment of cells with NO synthase inhibitor (N-nitro-l-arginine methyl ester [l-NAME]) also prevented CRP-mediated O(2)(-) production further strengthening CRP-mediated eNOS uncoupling. Additionally, CRP decreased eNOS phosphorylation at Ser1177 as well as increased phosphorylation at Thr495. CRP appears to mediate these effects through the Fcgamma receptors, CD32 and CD64. To conclude, CRP uncouples eNOS resulting in increased superoxide production, decreased NO production and altered eNOS phosphorylation.