L-cystathionine protects against oxidative stress and DNA damage induced by oxidized low-density lipoprotein in THP-1-derived macrophages.

Introduction: Oxidative stress in monocyte-derived macrophages is a significant pathophysiological process in atherosclerosis. L-cystathionine (L-Cth) acts as a scavenger for oxygen free radicals. However, the impact of L-Cth on macrophage oxidative stress during atherogenesis has remained unclear. This study aimed to investigate whether L-Cth affects oxidative stress in THP-1-derived macrophages and its subsequent effects on DNA damage and cell apoptosis. Methods: We established a cellular model of oxLDL-stimulated macrophages. The content of superoxide anion, H2O2, NO, and H2S in the macrophage were in situ detected by the specific fluorescence probe, respectively. The activities of SOD, GSH-Px, and CAT were measured by colorimetrical assay. The protein expressions of SOD1, SOD2, and iNOS were detected using western blotting. The DNA damage and apoptosis in the macrophage was evaluated using an fluorescence kit. Results: The results demonstrated that oxLDL significantly increased the content of superoxide anion and H2O2, the expression of iNOS protein, and NO production in macrophages. Conversely, oxLDL decreased the activity of antioxidants GSH-Px, SOD, and CAT, and downregulated the protein expressions of SOD1 and SOD2 in macrophages. However, treatment with L-Cth reduced the levels of superoxide anion, H2O2, and NO, as well as the protein expression of iNOS induced by oxLDL. Moreover, L-Cth treatment significantly enhanced GSH-Px, SOD, and CAT activity, and upregulated the expressions of SOD1 and SOD2 proteins in macrophages treated with oxLDL. Furthermore, both L-Cth supplementation and activation of endogenous L-Cth production suppressed DNA damage and cell apoptosis in oxLDL-injured macrophages, whereas inhibition of endogenous L-Cth exacerbated the deleterious effects of oxLDL. Conclusion: These findings suggest that L-Cth exerts a pronounced inhibitory effect on the oxidative stress, subsequent DNA damage and cell apoptosis in oxLDL-stimulated THP-1 monocytes. This study deepens our understanding of the pathogenesis of macrophage-related cardiovascular pathology.

Endogenous Hydrogen Sulfide Persulfidates Caspase-3 at Cysteine 163 to Inhibit Doxorubicin-Induced Cardiomyocyte Apoptosis.

Doxorubicin (DOX) is an efficient antitumor anthracycline drug, but its cardiotoxicity adversely affects the prognosis of the patients. In this study, we explored whether endogenous gasotransmitter hydrogen sulfide (H2S) could protect against DOX-induced cardiomyocyte apoptosis and its mechanisms. The results indicated that DOX significantly downregulated endogenous H2S production and endogenous synthetase cystathionine γ-lyase (CSE) expression and obviously stimulated the apoptosis in H9C2 cells. The supplement of H2S donor sodium hydrosulfide (NaHS) or overexpression of CSE inhibited DOX-induced H9C2 cell apoptosis. DOX enhanced the activities of caspase family members in cardiomyocytes, while NaHS attenuated DOX-enhanced caspase-3, caspase-2, and caspase-9 activities by 223.1%, 73.94%, and 52.29%, respectively. Therefore, taking caspase-3 as a main target, we demonstrated that NaHS or CSE overexpression alleviated the cleavage of caspase-3, suppressed caspase-3 activity, and inhibited the cleavage of poly ADP-ribose polymerase (PARP). Mechanistically, we found that H2S persulfidated caspase-3 in H9C2 cells and human recombinant caspase-3 protein, while the thiol-reducing agent dithiothreitol (DTT) abolished H2S-induced persulfidation of caspase-3 and thereby prevented the antiapoptotic effect of H2S on caspase-3 in H9C2 cells. The mutation of caspase-3 C148S and C170S failed to block caspase-3 persulfidation by H2S in H9C2 cells. However, caspase-3 C163S mutation successfully abolished the effect of H2S on caspase-3 persulfidation and the corresponding protection of H9C2 cells. Collectively, these findings indicate that endogenous H2S persulfidates caspase-3 at cysteine 163, inhibiting its activity and cardiomyocyte apoptosis. Sufficient endogenous H2S might be necessary for the protection against myocardial cell apoptosis induced by DOX. The results of the study might open new avenues with respect to the therapy of DOX-stimulated cardiomyopathy.

Nitric oxide inhibits endothelial cell apoptosis by inhibiting cysteine-dependent SOD1 monomerization.

Endothelial cell apoptosis is an important pathophysiology in many cardiovascular diseases. The gasotransmitter nitric oxide (NO) is known to regulate cell survival and apoptosis. However, the mechanism underlying the effect of NO remains unclear. In this research, by targeting cytosolic copper/zinc superoxide dismutase (SOD1) monomerization, we aimed to explore how NO inhibited endothelial cell apoptosis. We showed that treatment with the NO synthase (NOS) inhibitor nomega-nitro-l-arginine methyl ester hydrochloride (L-NAME) significantly decreased the endogenous NO content of endothelial cells, facilitated the formation of SOD1 monomers, inhibited dismutase activity, and promoted reactive oxygen species (ROS) accumulation in human umbilical vein endothelial cells (HUVECs); by contrast, supplementation with the NO donor sodium nitroprusside (SNP) upregulated NO content, prevented the formation of SOD1 monomers, enhanced dismutase activity, and reduced ROS accumulation in L-NAME-treated HUVECs. Mechanistically, tris(2-carboxyethyl) phosphine hydrochloride (TCEP), a specific reducer of cysteine thiol, increased SOD1 monomer formation, thus preventing the NO-induced increase in dismutase activity and the decrease in ROS. Furthermore, SNP inhibited HUVEC apoptosis caused by the decrease in endogenous NO, whereas TCEP abolished this protective effect of SNP. In summary, our data reveal that NO protects endothelial cells against apoptosis by inhibiting cysteine-dependent SOD1 monomerization to enhance SOD1 activity and inhibit oxidative stress.

Compensatory role of endogenous sulfur dioxide in nitric oxide deficiency-induced hypertension.

OBJECTIVE: This study aimed to determine the communicational pattern of gaseous signaling molecules sulfur dioxide (SO2) and nitric oxide (NO) between vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs), and elucidate the compensatory role and significance of endogenous SO2 in the development of hypertension due to NO deficiency. APPROACH AND RESULTS: Blood pressure was monitored by the tail-cuff and implantable physiological signal telemetry in L-nitro-arginine methyl ester (l-NAME)-induced hypertensive mice, and structural alterations of mouse aortic vessels were detected by the elastic fiber staining method. l-NAME-treated mice showed decreased plasma NO levels, increased SO2 levels, vascular remodeling, and increased blood pressure, and application of l-aspartate-ß-hydroxamate, which inhibits SO2 production, further aggravated vascular structural remodeling and increased blood pressure. Moreover, in a co-culture system of HAECs and HASMCs, NO from HAECs did not influence aspartate aminotransferase (AAT)1 protein expression but decreased AAT1 activity in HASMCs, thereby resulting in the inhibition of endogenous SO2 production. Furthermore, NO promoted S-nitrosylation of AAT1 protein in HASMCs and purified AAT1 protein. Liquid chromatography with tandem mass spectrometry showed that the Cys192 site of AAT1 purified protein was modified by S-nitrosylation. In contrast, dithiothreitol or C192S mutations in HASMCs blocked NO-induced AAT1 S-nitrosylation and restored AAT1 enzyme activity. CONCLUSION: Endothelium-derived NO inhibits AAT activity by nitrosylating AAT1 at the Cys192 site and reduces SO2 production in HASMCs. Our findings suggest that SO2 acts as a compensatory defense system to antagonize vascular structural remodeling and hypertension when the endogenous NO pathway is disturbed.

Endogenous SO2 Controls Cell Apoptosis: The State-of-the-Art.

SO2, previously known as the product of industrial waste, has recently been proven to be a novel gasotransmitter in the cardiovascular system. It is endogenously produced from the metabolism pathway of sulfur-containing amino acids in mammalians. Endogenous SO2 acts as an important controller in the regulation of many biological processes including cardiovascular physiological and pathophysiological events. Recently, the studies on the regulatory effect of endogenous SO2 on cell apoptosis and its pathophysiological significance have attracted great attention. Endogenous SO2 can regulate the apoptosis of vascular smooth muscle cells, endothelial cells, cardiomyocytes, neuron, alveolar macrophages, polymorphonuclear neutrophils and retinal photoreceptor cells, which might be involved in the pathogenesis of hypertension, pulmonary hypertension, myocardial injury, brain injury, acute lung injury, and retinal disease. Therefore, in the present study, we described the current findings on how endogenous SO2 is generated and metabolized, and we summarized its regulatory effects on cell apoptosis, underlying mechanisms, and pathophysiological relevance.

Changes in prevalence of nosocomial infection pre- and post-COVID-19 pandemic from a tertiary Hospital in China.

BACKGROUND: Nosocomial infections (NIs) are an important cause of mortality, and increasing evidence reveals that the prevalence of NIs can be reduced through effective prevention and control measures. The aim of this study was to investigate the impact of the prevention and control measures for the COVID-19 pandemic on NIs. METHODS: A retrospective study was conducted to analyze the prevalence of NIs before and after COVID-19 pandemic for 6 months in the Children's Hospital of Soochow University. RESULTS: A total of 39,914 patients in 2019 and 34,645 patients in 2020 were admitted to the hospital during the study. There were 1.39% (481/34645) of patients with NIs in 2020, which was significantly lower than the 2.56% (1021/39914) of patients in 2019. The rate of critical and fatal cases was also decreased. In addition, the rate of appropriate handwashing, the number of protective gloves and aprons used per person and the number of healthcare staff per patients were significantly increased. Except for the ICU, the prevalence of nosocomial infection in most departments decreased from 2019 to 2020. Regarding the source of infections, a significant reduction was mainly observed in respiratory (0.99% vs 0.42%, p = 0.000) and digestive tract (0.63% vs 0.14%, p = 0.000). The microorganism analysis of respiratory infections indicated an obvious decline in acinetobacters and fungi. The most significant decline of pathogens in gastrointestinal infections was observed for rotavirus. The comparison of catheter-related nosocomial infections between 2019 and 2020 did not show significant differences. CONCLUSIONS: The prevention and control measures for the COVID-19 pandemic have reduced the nosocomial infection in almost all departments, except the ICU, mainly regarding respiratory, gastrointestinal, and oral infections, while catheter-related infections did not show any differences.

Nano-Mechanical Properties and Creep Behavior of Ti6Al4V Fabricated by Powder Bed Fusion Electron Beam Additive Manufacturing.

Effects of scanning strategy during powder bed fusion electron beam additive manufacturing (PBF-EB AM) on microstructure, nano-mechanical properties, and creep behavior of Ti6Al4V alloys were compared. Results show that PBF-EB AM Ti6Al4V alloy with linear scanning without rotation strategy was composed of 96.9% α-Ti and 2.7% ß-Ti, and has a nanoindentation range of 4.11-6.31 GPa with the strain rate ranging from 0.001 to 1 s-1, and possesses a strain-rate sensitivity exponent of 0.053 ± 0.014. While PBF-EB AM Ti6Al4V alloy with linear and 90° rotate scanning strategy was composed of 98.1% α-Ti and 1.9% ß-Ti and has a nanoindentation range of 3.98-5.52 GPa with the strain rate ranging from 0.001 to 1 s-1, and possesses a strain-rate sensitivity exponent of 0.047 ± 0.009. The nanohardness increased with increasing strain rate, and creep displacement increased with the increasing maximum holding loads. The creep behavior was mainly dominated by dislocation motion during deformation induced by the indenter. The PBF-EB AM Ti6Al4V alloy with only the linear scanning strategy has a higher nanohardness and better creep resistance properties than the alloy with linear scanning and 90° rotation strategy. These results could contribute to understanding the creep behavior of Ti6Al4V alloy and are significant for PBF-EB AM of Ti6Al4V and other alloys.

Metabolic Reprogramming of Vascular Endothelial Cells: Basic Research and Clinical Applications.

Vascular endothelial cells (VECs) build a barrier separating the blood from the vascular wall. The vascular endothelium is the largest endocrine organ, and is well-known for its crucial role in the regulation of vascular function. The initial response to endothelial cell injury can lead to the activation of VECs. However, excessive activation leads to metabolic pathway disruption, VEC dysfunction, and angiogenesis. The pathways related to VEC metabolic reprogramming recently have been considered as key modulators of VEC function in processes such as angiogenesis, inflammation, and barrier maintenance. In this review, we focus on the changes of VEC metabolism under physiological and pathophysiological conditions.

Power controllable gain switched fiber laser at ~ 3 µm and ~ 2.1 µm.

Based on a hybrid pumping method consisting of a 1150 nm continuous-wave pump source and a 1950 nm pulsed pump source, we demonstrate a power controllable gain-switched fiber laser in dual wavebands at ~ 3 µm and ~ 2.1 µm. Different pumping schemes for pumping a Ho3+-doped ZBLAN fiber are studied. Using only the 1950 nm pulsed pump source, ~ 2.1 µm gain-switched pulses with single and double pulses are obtained separately at different pump powers. This phenomenon indicates that the 1950 nm pulsed pump source acts as a modulator to trigger different states of the ~ 2.1 µm pulses. Moreover, by fixing the 1150 nm pump power at 3.259 W and adjusting the 1950 nm pump power, the output power of the ~ 2.1 µm gain-switched pulsed laser is flexibly controlled while the ~ 3 µm laser power is almost unchanged, inducing the maximum output powers of 167.96 mW and 260.27 mW at 2910.16 nm and 2061.65 nm, respectively. These results suggest that the comparatively low power of the ~ 2.1 µm gain-switched pulsed laser in dual-waveband laser can be efficiently overcome by reasonably controlling the 1950 nm pump power.

Sulphenylation of CypD at Cysteine 104: A Novel Mechanism by Which SO2 Inhibits Cardiomyocyte Apoptosis.

Objectives: The study was designed to explore the role of endogenous gaseous signaling molecule sulfur dioxide (SO2) in the control of cardiomyocyte apoptosis and its molecular mechanisms. Methods: Neonatal mouse cardiac myocytes (NMCMs) and H9c2 cells were used in the cell experiments. The endogenous SO2 pathway including SO2 level and the expression of SO2-generating enzyme aspartate aminotransferase 1/2 (AAT1/2) were detected in NMCMs. The apoptosis of cardiomyocytes was examined by a TUNEL assay. The cleavage and the activity of apoptotic proteins caspase9 and caspase3 were measured. The content of ATP, the opening of mitochondrial permeability transition pore (mPTP), and the cytochrome c (cytc) leakage were detected by immunofluorescence. The sulphenylation of cyclophilin-D (CypD) was detected by biotin switch analysis. The four CypD mutant plasmids in which cysteine sites were mutated to serine were constructed to identify the SO2-affected site in vitro. Results: ISO down-regulated the endogenous SO2/AAT pathway of cardiomyocytes in association with a significant increase in cardiomyocyte apoptosis, demonstrated by the increases in apoptosis, cleaved-caspase3/caspase3 ratio, and caspase3 activity. Furthermore, ISO significantly reduced ATP production in H9c2 cells, but the supplement of SO2 significantly restored the content of ATP. ISO stimulated mPTP opening, resulting in an increase in the release of cytc, which further increased the ratio of cleaved caspase9/caspase9 and enhanced the protein activity of caspase9. While, the supplementation of SO2 reversed the above effects. Mechanistically, SO2 did not affect CypD protein expression, but sulphenylated CypD and inhibited mPTP opening, resulting in an inhibition of cardiomyocyte apoptosis. The C104S mutation in CypD abolished SO2-induced sulphenylation of CypD, and thereby blocked the inhibitory effect of SO2 on the mPTP opening and cardiomyocyte apoptosis. Conclusion: Endogenous SO2 sulphenylated CypD at Cys104 to inhibit mPTP opening, and thus protected against cardiomyocyte apoptosis.

Post-translational Modifications of IκBα: The State of the Art.

The nuclear factor-kappa B (NF-κB) signaling pathway regulates a variety of biological functions in the body, and its abnormal activation contributes to the pathogenesis of many diseases, such as cardiovascular and respiratory diseases and cancers. Therefore, to ensure physiological homeostasis of body systems, this pathway is strictly regulated by IκBα transcription, IκBα synthesis, and the IκBα-dependent nuclear transport of NF-κB. Particularly, the post-translational modifications of IκBα including phosphorylation, ubiquitination, SUMOylation, glutathionylation and hydroxylation are crucial in the abovementioned regulatory process. Because of the importance of the NF-κB pathway in maintaining body homeostasis, understanding the post-translational modifications of IκBα can not only provide deeper insights into the regulation of NF-κB pathway but also contribute to the development of new drug targets and biomarkers for the diseases.

Negative auto-regulation of sulfur dioxide generation in vascular endothelial cells: AAT1 S-sulfenylation.

Recently, endogenous sulfur dioxide (SO2) has been found to exert an important function in the cardiovascular system. However, the regulatory mechanism for SO2 generation has not been entirely clarified. Hence, we aimed to explore the possible auto-regulation of endogenous SO2 generation and its mechanisms in vascular endothelial cells. We showed that SO2 did not affect the protein expression of aspartate aminotransferase 1 (AAT1), a major SO2 synthesis enzyme, but significantly inhibited AAT activity in primary human umbilical vein endothelial cells (HUVECs) and porcine purified AAT1 protein. An AAT1 enzymatic kinetic study showed that SO2 reduced the Vmax (1.89 ± 0.10 vs 2.55 ± 0.12, µmol/mg/min, P < 0.05) and increased the Km (35.97 ± 9.54 vs 19.33 ± 1.76 µmol/L, P < 0.05) values. Furthermore, SO2 induced S-sulfenylation of AAT1 in primary HUVECs and purified AAT1 protein. LC-MS/MS analysis indicated that SO2 sulfenylated AAT1 at Cys192. Mechanistically, thiol reductant DTT treatment or C192S mutation prevented SO2-induced AAT1 sulfenylation and the subsequent inhibition of AAT activity in purified AAT1 protein and primary HUVECs. Our findings reveal, for the first time, a mechanism of auto-regulation of SO2 generation through sulfenylation of AAT1 at Cys192 to suppress AAT activity in vascular endothelial cells. These findings will greatly deepen the understanding of regulatory mechanisms in the cardiovascular homeostasis.

Large aspect ratio gold nanorods (LAR-GNRs) for mid-infrared pulse generation with a tunable wavelength near 3 µm.

We report a tunable passively Q-switched fiber laser at the wavelengths near 3 µm, using large aspect ratio gold nanorods (LAR-GNRs) as a saturable absorber (SA) for the first time. The GNRs with a large average aspect ratio of up to ~20 were prepared using the seed-mediated growth method, which yielded a strong absorption band of 2.2-3 µm with a peak at ~2600 nm, stemming from longitudinal surface plasmon resonance (SPR). The corresponding nonlinear absorption was characterized using 2.87 µm ultrafast pulses, giving the modulation depth of 8.89%, saturation intensity of 14.9 MW/cm2, and nonsaturation loss of 39.9%. When introducing the material into a tunable Ho3+/Pr3+ codoped ZBLAN fiber laser as a SA, stable Q-switched pulses with a tunable wavelength within 2.83-2.88 µm were achieved. The largest output power of 30.8 mW, repetition rate of 78.12 kHz, and narrowest pulse width of 2.18 µs were simultaneously attained when tuned to ~2.865 µm at the pump power of 307.2 mW, while the largest pulse energy of 0.48 µJ was obtained at the longest tuning edge of 2.88 µm. Our work indicates that LAR-GNRs are a type of versatile broadband SA material available for the mid-infrared region.

Watt-level gain-switched fiber laser at 3.46 µm.

We demonstrate a gain-switched fiber laser, yielding a maximum average power of 1.04 W at 3.46 µm, which is the current record of a pulsed rare-earth-doped fiber laser at the wavelength beyond 3 µm, to our knowledge. The corresponding pulse energy is 10.4 µJ with a repetition rate of 100 kHz. A dual-wavelength pumping scheme consisting of a home-made 1950 nm passively Q-switched fiber laser system with a µs-scale pulse width. A 976 nm continuous wave laser diode was used to gain-switch a double-cladding Er-doped ZBLAN fiber laser cavity. Possible laser-quenching behavior during a single-pump pulse was circumvented for the moderate pump peak power and relatively large-pump pulse width. Synchronous gain-switched pulses were achieved with a tunable repetition rate at a wide range of 55~120 kHz, which is the highest gain-switching repetition rate at this band and only limited by our pulsed-pump source. Moreover, the significance of pump pulse width for repetition rate improvement is also discussed. These results provide an available way to produce high-power pulses at the mid-infrared range of 3~5 µm.

Microstructure and Properties of Porous High-N Ni-Free Austenitic Stainless Steel Fabricated by Powder Metallurgical Route.

Porous high-N Ni-free austenitic stainless steel was fabricated by a powder metallurgical route. The microstructure and properties of the prepared porous austenitic stainless steel were studied. Results reveal that the duplex stainless steel transforms into austenitic stainless steel after nitridation sintering for 2 h. The prepared high-N stainless steel consists of γ-Fe matrix and FCC structured CrN. Worm-shaped and granular-shaped CrN precipitates were observed in the prepared materials. The orientation relationship between CrN and austenite matrix is [011]CrN//[011]γ and (-1-11)CrN//(1-11)γ. Results show that the as-fabricated porous high-nitrogen austenitic stainless steel features a higher mechanical property than common stainless steel foam. Both compressive strength and Young’s modulus decrease with an increase in porosity. The 3D morphology of the prepared porous materials presents good pore connectivity. The prepared porous high-N Ni-free austenitic stainless steel has superior pore connectivity, a good combination of compressive strength and ductility, and low elastic modulus, which makes this porous high-N Ni-free austenitic stainless steel very attractive for metal foam applications.