Antimicrobial action of carbon monoxide-releasing compounds

Carbon monoxide (CO) is endogenously produced in the human body, mainly from the oxidation of heme catalyzed by heme oxygenase (HO) enzymes. The induction of HO and the consequent increase in CO production play important physiological roles in vasorelaxation and neurotransmission and in the immune system. The exogenous administration of CO gas and CO-releasing molecules (CO-RMs) has been shown to induce vascular effects and to alleviate hypoxia-reoxygenation injury of mammalian cells. In particular, due to its anti-inflammatory, antiapoptotic, and antiproliferative properties, CO inhibits ischemic-reperfusion injury and provides potent cytoprotective effects during organ and cell transplantation. In spite of these findings regarding the physiology and biology of mammals, nothing is known about the action of CO on bacteria. In the present work, we examined the effect of CO on bacterial cell proliferation. Cell growth experiments showed that CO caused the rapid death of the two pathogenic bacteria tested, Escherichia coli and Staphylococcus aureus, particularly when delivered through organometallic CO-RMs. Of importance is the observation that the effectiveness of the CO-RMs was greater in near-anaerobic environments, as many pathogens are anaerobic organisms and pathogen colonization occurs in environments with low oxygen concentrations. Our results constitute the first evidence that CO can be utilized as an antimicrobial agent. We anticipate our results to be the starting point for the development of novel types of therapeutic drugs designed to combat antibiotic-resistant pathogens, which are widespread and presently a major public health concern.     

外源性一氧化碳分子对脓毒症时心脏炎症反应的抑制作用及机制

目的:探讨外源性一氧化碳释放分子2(CORM-2)对脓毒症时心脏炎症反应的抑制作用和心脏功能的影响。方法:将45只雄性BALB/c小鼠按随机数字表法分为假手术组、盲肠结扎和穿孔术(CLP)组和CLP+CORM-2组。CLP+CORM-2组除伤后使用CORM-2外,其他处理同CLP组。于伤后24h检测小鼠血清天门冬氨酸氨基转移酶(AST)和乳酸脱氢酶(LDH)水平;用流式细胞术检测心肌细胞凋亡率;同时用彩色多普勒超声成像系统进行心脏超声检查。结果:与假手术组比较,24hCLP组血浆AST、LDH的水平明显增加,心肌细胞凋亡率明显增高,心脏超声检查显示LVEF、LVFS均显著低于假手术组(P<0.05);CLP+CORM-2组AST、LDH的水平降低,心肌细胞凋亡率明显下降,心脏超声检查显示LVEF、LVFS均显著提高(P<0.05)。结论:外源性CORM-2能明显抑制脓毒症心脏炎症反应,降低心肌细胞凋亡率,提高左室泵血能力,从而有效防止脓毒症时心肌损伤,提高心脏功能。     

Carbon monoxide-releasing molecules modulate leukocyte-endothelial interactions under flow

Carbon monoxide (CO) generated by the enzyme heme oxygenase during the breakdown of heme is known to mediate a number of biological effects. Here, we investigated whether CO liberated from a water-soluble CO-releasing molecule (CO-RM) is capable of modulating leukocyte-endothelial interactions. Tricarbonylchoro(glycinato)ruthenium (II) (CORM-3), a fast CO releaser, proved to be anti-inflammatory in two distinct models of acute inflammation in vivo. In both cases, a significant reduction in neutrophil extravasation was observed. Subsequent in vitro static experiments showed that CORM-3 produced a direct effect on neutrophil (polymorphonuclear neutrophil; PMN) adhesion molecule expression; dose-dependently inhibiting platelet-activating factor stimulated CD11b up-regulation and L-selectin shedding, whereas no effect was observed on up-regulation of human umbilical vein endothelial cell (HUVEC) adhesion molecules intercellular adhesion molecule-1 or E-selectin nor on interleukin-8 chemokine production. In addition, when PMN interaction with HUVECs was studied, an inhibitory effect of CORM-3 on cell capture and rolling was observed. The effect of CORM-3 on PMN CD11b expression was mimicked by the incubation of PMN with the selective large potassium channel opener 1,3-dihydro-1-(2-hydroxy-5-(trifluoromethyl)-phenyl)-5-(trifluoromethyl)-2H-benzimidazol-2-one (NS-1619), which suggests that CORM-3 actions in this instance are mediated, at least in part, via opening of this channel. In conclusion, we have reported that CORM-3 possesses acute anti-inflammatory effects in vivo and that these are probably the result of targeting PMN activation and rolling upon the endothelium.     

外源性一氧化碳分子对脓毒症时血小板膜糖蛋白过度表达和血小板活化的抑制作用及机制

目的 探讨外源性一氧化碳释放分子(CORM-2)对脓毒症时血小板膜糖蛋白表达和血小板活化的抑制作用.方法 将120只雄性BALB/c小鼠按随机数字表法分为正常对照组、盲肠结扎+穿孔术(CLP)组、CLP+无活性CORMS(iCORM-2)组和CLP+CORM-2组.CLP+CORM-2组除伤后使用CORM-2外,其他处理同CLP组.于伤后6 h、12 h、24 h分别检测小鼠血浆纤维蛋白原(FIB)、D-二聚体(D-D)的水平;全血电阻法检测血小板聚集功能;用流式细胞术检测血小板膜糖蛋白CD61和CD62p的表达水平;同时Western Blot检测造血系细胞特异蛋白-1(HS1)分子磷酸化水平.结果 与假手术组比较,12 h、24 h CLP组血浆FIB、D-D的水平明显增加[分别为(4.65±0.73)g/L,(5.76±0.88)g/L和(229.93±62.91)mg/L,(182.96±46.32)mg/L,P<0.01)],血小板聚集率明显增高,血小板膜糖蛋白CD61和CD62p的表达增加[分别为(94.87±11.22)%,(95.93±7.43)%和(34.81±4.76)%,(32.88±6.94)%,P<0.05)].HS1分子磷酸化水平增加;CLP+CORM-2组血浆FIB、D-D的水平均显著降低[分别为(3.32±0.42)g/L,(3.68±0.46)g/L和(169.57±35.14)mg/L,(141.82±18.46)mg/L,P<0.05)],血小板聚集率下降明显,膜糖蛋白CD61和CD62p的表达也得到有效下调[分别为(72.12±11.67)%,(73.68±8.76)%和(21.38±1.61)%,(24.65±5.96)%,P<0.05],HS1分子磷酸化水平得到有效抑制.结论 外源性CORM-2能明显下调脓毒症时血小板膜糖蛋白CD61和CD62p的表达以及HS1分子磷酸化水平,并抑制血浆NB、D-D的升高,继而降低血小板黏附及聚集率,有效抑制脓毒症时血小板的过度活化.     

A series of Mn(i) photo-activated carbon monoxide-releasing molecules with benzimidazole coligands: synthesis,structural characterization,CO releasing properties and biological activity evaluation

Five Mn(i) photo-activated carbon monoxide-releasing molecules (photo-CORMs) with benzimidazole coligands, namely [MnBr(CO)₃L1] (1, L1 = 2-(2-pyridyl)benzimidazole), [Mn(CO)₂L1(PPh₃)₂](ClO₄) (2), [MnBr(CO)₃L2] (3, L2 = 2,2′-bisbenzimidazole), [MnBr(CO)₃L3]·CH₃OH (4, L3 = 2,6-bis(benzimidazole-2′-yl)pyridine) and fac-[MnBr(CO)₃L4] (5, L4 = 2,4-bis(benzimidazole-2′-yl) pyridine) were synthesized by reactions of MnBr(CO)₅ with complexes L1–L4, respectively, and characterized via single crystal X-ray diffraction, elemental analysis, ¹H-NMR, ¹³C-NMR, IR, UV-vis and fluorescence spectroscopy. The CO-release properties of 1–5 were investigated using the myoglobin assay and CO detection, and the results show that all of the complexes could release CO rapidly upon exposure to 365 nm UV light. Comparing their half-lives of CO release, we found that increasing the degree of unsaturation and conjugation of the ligand frame could be advantageous for prolonging the time of CO-release, and that the luminescence intensity of 1–5 could gradually be enhanced. The cellular fluorescence imaging tests demonstrate that these Mn(i) photo-CORMs can be taken up by human liver cells (HL-7702) and liver cancer cells (SK-Hep1), and exhibit good capabilities for bioimaging. A cell viability assay for SK-Hep1 shows that the anticancer activity of 3 is better than that of other complexes.

Five Mn(i) photo-activated carbon monoxide-releasing molecules were synthesized by reactions of MnBr(CO)₅ with L1–L4, and characterized via single crystal X-ray diffraction, ¹H-NMR, ¹³C-NMR, IR, UV-vis and fluorescence spectroscopy.     

A novel carbon monoxide-releasing molecule fully protects mice from severe malaria

Severe forms of malaria infection, such as cerebral malaria (CM) and acute lung injury (ALI), are mainly caused by the apicomplexan parasite Plasmodium falciparum. Primary therapy with quinine or artemisinin derivatives is generally effective in controlling P. falciparum parasitemia, but mortality from CM and other forms of severe malaria remains unacceptably high. Herein, we report the design and synthesis of a novel carbon monoxide-releasing molecule (CO-RM; ALF492) that fully protects mice against experimental CM (ECM) and ALI. ALF492 enables controlled CO delivery in vivo without affecting oxygen transport by hemoglobin, the major limitation in CO inhalation therapy. The protective effect is CO dependent and induces the expression of heme oxygenase-1, which contributes to the observed protection. Importantly, when used in combination with the antimalarial drug artesunate, ALF492 is an effective adjunctive and adjuvant treatment for ECM, conferring protection after the onset of severe disease. This study paves the way for the potential use of CO-RMs, such as ALF492, as adjunctive/adjuvant treatment in severe forms of malaria infection.     

Modulation of thrombin-induced neuroinflammation in BV-2 microglia by carbon monoxide-releasing molecule 3

Carbon monoxide-releasing molecules are emerging as a new class of pharmacological agents that regulate important cellular function by liberating CO in biological systems. Here, we examined the role of carbon monoxide-releasing molecule 3 (CORM-3) in modulating neuroinflammatory responses in BV-2 microglial cells, considering its practical application as a novel therapeutic alternative in the treatment of stroke. BV-2 microglia cells were incubated for 24 h in normoxic conditions with thrombin alone or in combination with interferon-gamma to simulate the inflammatory response. Cells were also subjected to 12 h of hypoxia and reoxygenated for 24 h in the presence of thrombin and interferon-gamma. In both set of experiments, the anti-inflammatory action of CORM-3 was evaluated by assessing its effect on nitric oxide production (nitrite levels) and tumor necrosis factor (TNF)-alpha release. CORM-3 (75 microM) did not show any cytotoxicity and markedly attenuated the inflammatory response to thrombin and interferon-gamma in normoxia and to a lesser extent in hypoxia as evidenced by a reduction in nitrite levels and TNF-alpha production. Inactive CORM-3, which does not liberate CO and is used as a negative control, failed to prevent the increase in inflammatory mediators. Blockade of endogenous CO production by tin protoporphyrin-IX did not change the anti-inflammatory activity of CORM-3, suggesting that CO liberated from the compound is responsible for the observed effects. In addition, inhibition of the mitogen-activated protein kinases phosphatidyl inositol 3 kinase and extracellular signal-regulated kinase amplified the anti-inflammatory effect of CORM-3. These results suggest that the anti-inflammatory activity of CORM-3 could be exploited to mitigate microglia activity in stroke and other neuroinflammatory diseases.     

The carbon monoxide-releasing molecule tricarbonyldichlororuthenium(II) dimer protects human osteoarthritic chondrocytes and cartilage from the catabolic actions of interleukin-1beta

We have investigated the effects of a carbon monoxide-releasing molecule, tricarbonyldichlororuthenium(II) dimer (CORM-2), on catabolic processes in human osteoarthritis (OA) cartilage and chondrocytes activated with interleukin-1beta. In these cells, proinflammatory cytokines induce the synthesis of matrix metalloproteinases (MMPs) and aggrecanases, including members of a disintegrin and metalloproteinase with thrombospondin domain (ADAMTS) family, which may contribute to cartilage loss. CORM-2 down-regulated MMP-1, MMP-3, MMP-10, MMP-13, and ADAMTS-5 in OA chondrocytes, and it inhibited cartilage degradation. These effects were accompanied by increased aggrecan synthesis and collagen II expression in chondrocytes. Our results also indicate that the inhibition of extracellular signal-regulated kinase 1/2 and p38 activation by CORM-2 may contribute to the maintenance of extracellular matrix homeostasis. These observations suggest that CORM-2 could exert chondroprotective effects due to the inhibition of catabolic activities and the enhancement of aggrecan synthesis.     

Bio-cleaning improves the mechanical properties of lignin-based carbon fibers

Production of carbon fibers (CF) using renewable precursors has gained importance particularly in the last decade to reduce the dependency on conventional petroleum-based precursors. However, pre-treatment of these renewable precursors is still similar to that of conventional ones. Little work is put into greener pre-treatments and their effects on the end products. This work focuses on the use of bio-cleaned lignin as a green precursor to produce CF by electrospinning. Bio-cleaned kraft lignin A (Bio-KLA) and uncleaned kraft lignin A (KLA) were used to explore the effect of bio-cleaning on the diameter and mechanical properties of lignin fibers and CF. The effect of electric field, lignin-to-poly(ethylene oxide) (PEO) ratio and PEO molecular weight (MW) were evaluated by 3³ factorial design using Design of Experiment (DOE). The electrospinning process parameters were optimized to obtain a balance between high elastic modulus and small fiber diameter. The model predicted optimized conditions were 50 kV m⁻¹ electric field, 95/5 lignin-to-PEO ratio and 1000 kDa MW of PEO. When compared to KLA, Bio-KLA CFs showed a 2.7-fold increase in elastic modulus, 2-fold increase in tensile strength and 30% decrease in fiber diameter under the same optimum conditions. The results clearly show that bio-cleaning improved the mechanical properties of lignin derived CF.

Waste lignin (KLA) and bio-cleaned lignin (Bio-KLA) precursors, used to produce parameter-optimized-electrospun carbon fibers showed improved mechanical properties for Bio-KLA.     

Bioactive constituents of brazilian red propolis

In a new propolis type, red Brazilian propolis, 14 compounds were identified (six of them new for propolis), among them simple phenolics, triterepenoids, isoflavonoids, prenylated benzophenones and a naphthoquinone epoxide (isolated for the first time from a natural source). Three of the major components demonstrated significant antimicrobial activity, and two (obtained as inseparable mixture) possessed radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH).     

Tuning residual chirality in carbon dots with anti-microbial properties

Chirality remains a critical consideration in drug development and design, as well as in applications of enantioselective recognition and sensing. However, the preparation of chiral nanomaterials requires extensive post synthetic modifications with a chiral agent, coupled with extensive purification. This limits the use and application of chiral nanomaterials. Herein, we report a facile, one-step microwave-assisted synthesis of chiral carbon dots through the reaction of l- and d-cysteine amino acid precursors and citric acid. We modulated the synthetic parameters to preserve and tune the residual chiral properties of the dots and demonstrate that the reaction conditions play a critical role in dictating the chiral behaviour of the dots. Finally, in a proof of concept application we demonstrated that the synthesized carbon dots, particularly d-carbon dots inhibit bacterial growth at a lower concentration than l-carbon dots. By varying bacterial strains and chirality of the carbon dots, concentrations ranging from 0.25–4 mg mL⁻¹ of the nanoparticles were required to inhibit microbial growth. The ability to preserve and tune chirality during synthesis can open up novel avenues and research directions for the development of enantioselective materials, as well as antibacterial films and surfaces.

Chiral carbon dots, prepared from the unnatural d-enantiomer of cysteine, inhibit the growth of Escherichia coli ATCC 25922 and MG1655 at a lower concentration than l-carbon dots, prepared from the l-enantiomer.     

Mechanical and thermal properties of carbon nanotubes in carbon nanotube fibers under tension–torsion loading

In carbon nanotube fibers (CNFs) fabricated by spinning methods, it is well-known that the mechanical and thermal performances of CNFs are highly dependent on the mechanical and thermal properties of the inherent CNTs. Furthermore, long CNTs are usually preferred to assemble CNFs because the interaction and entanglement between long CNTs are effectively stronger than between short CNTs. However, in CNFs fabricated using long CNTs, the interior carbon nanotubes (CNTs) inevitably undergo both tension and torsion loading when they are stretched, which would influence the mechanical and thermal performances of CNFs. Here, molecular dynamics (MD) simulations were carried out to study the mechanical and thermal properties of individual CNTs under tension–torsion loading. As for mechanical properties, it was found that both the fracture strength and Young''s modulus of CNTs decreased as the twist angle α increased. Besides, step-wise fracture happened due to stress concentration when the twisted CNTs are stretched. On the other hand, it could be seen that the thermal conductivity of CNTs decreased as α increased. This work presents the systematic investigation of the mechanical and thermal properties of CNTs under tension–torsion loading and provides a theoretical guideline for the design and fabrication of CNFs.

Systematically investigate the mechanical and thermal properties of SWCNT under tension and torsion loadings and provide references for fabricating next-generation super-CNF.     

Doping strategy,properties and application of heteroatom-doped ordered mesoporous carbon

To date, tremendous achievements have been made to produce ordered mesoporous carbon (OMC) with well-designed and controllable porous structure for catalysis, energy storage and conversion. However, OMC as electrode material suffers from poor hydrophilicity and weak electrical conductivity. Numerous attempts and much research interest have been devoted to dope different heteroatoms in OMC as the structure defects to enhance its performance, such as nitrogen, phosphorus, sulphur, boron, and multi heteroatoms. Unfortunately, the “how–why–what” question for the heteroatom-doped OMC has not been summarized in any published reports. Therefore, this review focuses on the functionalization strategies of heteroatoms in OMC and the corresponding process characteristics, including in situ method, post treatment method, and chemical vapor deposition. The fundamentally influencing mechanisms of various heteroatoms in electrochemical property and porous structure are summarized in detail. Furthermore, this review provides an updated summary about the applications of different heteroatom-doped OMC in supercapacitor, electrocatalysis, and ion battery during the last decade. Finally, the future challenges and research strategies for heteroatom-doped OMC are also proposed.

To date, tremendous achievements have been made to produce ordered mesoporous carbon (OMC) with well-designed and controllable porous structure for catalysis, energy storage and conversion.     

Cellobiose/mannitol test: physiological properties of probe molecules and influence of extraneous factors

The influence of gastric emptying, intestinal transit, renal and hepatic function, and variations in the timing of urine collections, on the cellobiose/mannitol test of intestinal permeability has been studied. None of these extraneous factors influences the cellobiose/mannitol recovery ratio, and there is only a modest effect of renal function on urinary mannitol recovery. Cellobiose is almost totally recovered in the urine within 10 h of intravenous injection, whilst mannitol is less completely recovered, perhaps due to hepatic metabolism. The simultaneous administration of two probe molecules in the cellobiose/mannitol test, and the use of a ratio to express results, thus achieves the desired object of minimising the effect of extraneous factors on the test result. The cellobiose/mannitol test is therefore not subject to the limitations of previous tests of intestinal permeability using orally administered probe molecules, and is widely applicable as a screening test for coeliac disease.     

Energetics and optical properties of carbon impurities in rutile TiO2

Titanium dioxide is one of the most promising materials for many applications such as photovoltaics and photocatalysis. Non-metal doping of TiO₂ is widely used to improve the photoconversion efficiency by shifting the absorption edge from the UV to visible-light region. Here, we employ hybrid density-functional calculations to investigate the energetics and optical properties of carbon (C) impurities in rutile TiO₂. The predominant configurations of the C impurities are identified through the calculated formation energies under O-poor and O-rich growth conditions. Under the O-poor condition, we find that C occupying the oxygen site (C_O) is energetically favorable for Fermi-level values near the conduction band minimum (n-type TiO₂), and acts as a double acceptor. Under the O-rich condition, the C_i–V_Ti complex is energetically favorable, and is exclusively stable in the neutral charge state. We also find that interstitial hydrogen (H_i) can bind to C_O, forming a C_O–H_i complex. Our results suggest that C_O and C_O–H_i are a cause of visible-light absorption under oxygen deficient growth conditions.

The substitutional C on O site and its complex with H are a cause of visible-light absorption in rutile TiO₂.     

Electrochemical properties of kenaf-based activated carbon monolith for supercapacitor electrode applications

Activated carbon monoliths of kenaf (ACMKs) were prepared by moulding kenaf fibers into a column-shape monolith and then carrying out pyrolysis at 500, 600, 700 or 800 °C, followed by activation with KOH at 700 °C. Then, the sample was characterized using thermogravimetric analyzer (TGA), field-emission scanning electron microscopy (FE-SEM), field-emission transmission electron microscopy (FE-TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD) and N₂ sorption instruments. The prepared ACMK was subjected to electrochemical property evaluation via cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). The GCD study using a three-electrode system showed that the specific capacitance decreased with higher pyrolysis temperature (PYT) with the ACMK pyrolyzed at 500 °C (ACMK-500) exhibiting the highest specific capacitance of 217 F g⁻¹. A two-electrode system provided 95.9% retention upon a 5000 cycle test as well as the specific capacitance of 212 F g⁻¹, being converted to an energy density of 6 W h kg⁻¹ at a power density of 215 W kg⁻¹.

Monolithic carbon from kenaf-based fiber for supercapacitor electrode application provided a specific capacitance of 212 F g⁻¹via GCD at 1 A g⁻¹, converting to an energy density of 6 W h kg⁻¹ at the power density of 215 W kg⁻¹ as well as 95.9% retention upon 5000 cycling test.     

外源性一氧化碳释放分子2对大鼠脊髓缺血再灌注损伤的保护作用研究

目的探讨外源性一氧化碳释放分子2(CORM2)对大鼠脊髓缺血再灌注损伤的保护作用与相关机制。方法将30只健康雄性Wistar大鼠分为实验组、对照组、空白组,每组各10只。实验组在造模前1h尾静脉注射外源性CORM2。实验组和对照组采用相同的方法造模。对照组造模后1h注射与实验组相同剂量的生理盐水。空白组仅完成开腹和关腹操作,并术后1h注射与实验组相同剂量的生理盐水。在术后不同时间进行神经行为学评分(Tarlov评分)、脊髓组织病理学检查和白细胞介素-6(IL-6)、肿瘤坏死因子-α(TNF-α)检测。结果再灌注后不同时间点,实验组Tarlov评分均高于对照组,但实验组和对照组Tarlov评分均低于空白组(P0.05)。缺血再灌注48h后,对照组脊髓组织标本可见损伤及坏死神经元,表现为细胞核固缩或溶解,细胞质中的尼氏体消失;空白组脊髓组织标本中可见正常神经元,表现为结构呈多角形,细胞质中可见尼氏体;实验组脊髓组织标本中的神经元坏死表现介于对照组和空白组之间。缺血再灌注48h,实验组与对照组IL-6、TNF-α表达水平均高于空白组,但实验组IL-6、TNF-α表达水平低于对照组(P0.05)。结论外源性CORM2可抑制炎性因子的表达,对大鼠脊髓缺血再灌注损伤具有一定的保护作用。     

胶质细胞源性神经营养因子的生物活性特征

胶质细胞源性神经营养因子(glialcell-linederivedneurotrophicfacto,GDNF)是近年来才被发现而且被证明有确定生物学活性的一种神经营养因子,其在促进神经细胞的功能维持和损伤修复方面有其他神经营养因子不能比拟的强效作用,对多巴胺能神经元的特异性营养作用已为众多学者认可,但其作用并不只限于此。关于其受体的研究也逐渐开展并深入,研究发现GDNF的各种受体是其发挥作用的必要介导。虽然目前大多限于基础研究,但已经取得了相当的成果,可以预见GDNF将会有很好的临床应用前景。