Hypoxia in vivo induces oligozoospermia, azoospermia, and degeneration of the germinal epithelium, but the underlying molecular mechanism of this induction is not fully clarified. The aim of this ...study was to investigate the role of the death receptor pathway and the mitochondrial pathway in hypoxia‐induced apoptosis of mouse GC‐2spd (GC‐2) cells and the relationship between HIF‐1α and apoptosis of GC‐2 cells induced by hypoxia. GC‐2 cells were subjected to 1% oxygen for 48 hr. Apoptosis was detected by flow cytometry, TUNEL staining, LDH, caspase‐3/8/9 in the absence and presence of HIF‐1α siRNA. The protein levels of apoptosis‐related markers were determined by Western blot in the presence and absence of HIF‐1α siRNA. Mitochondrial transmembrane potential change was observed by in situ JC‐1 staining. Cell viability was assessed upon treatment of caspase‐8 and 9 inhibitors. The results indicated that hypoxia at 1% oxygen for 48 hr induced apoptosis of GC‐2 cells. A prolonged exposure of GC‐2 cells to hypoxic conditions caused downregulation of c‐FLIP, DcR2 and Bcl‐2 and upregulation of DR5, TRAIL, Fas, p53, and Bax, with an overproduction of caspase‐3/8/9. Moreover, hypoxia at this level had an effect on mitochondrial depolarization. In addition, specific inhibitors of caspase‐8/9 partially suppressed hypoxia‐induced GC‐2 cell apoptosis, and the anti‐apoptotic effects of the caspase inhibitors were additive. Of note, HIF‐1α knockdown attenuated hypoxia and induced apoptosis of GC‐2 cells. In conclusion, our data suggest that the death receptor pathway and mitochondrial pathway, which are likely mediated by HIF‐1α, contribute to hypoxia‐induced GC‐2 cell apoptosis.
It has been known that hypoxia induces male infertility with the underlying mechanisms to be clarified. This study determined that the death receptor pathway and mitochondrial pathway, which are likely mediated by HIF‐1α, contribute to hypoxia‐induced apoptosis of mouse pachytene spermatocytes.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Abnormal spermatogenesis is an important pathophysiological process underlying male infertility. Apoptosis of spermatogenic cells and disruption of ectoplasmic specialization (ES) have been ...characterized as the key biological events of this disorder. Under physiological and pathophysiological conditions (such as exposure to starvation, environmental chemicals, radiation), autophagy is activated in spermatogenic or Sertoli cells in order to maintain survival of the spermatogenic cells by inhibiting spermatogenic cell apoptosis and stabilizing the integrity of ES via degradation of PDZ and LIM domain 1 (PDLIM1), a negative regulator of cytoskeletal organization. Here, we review the most recent research progress towards understanding the pivotal effects of autophagy on spermatogenesis. Summary Sentence Autophagy plays a prosurvival role in spermatogenic cells and promotes stabilization of the integrity of ES, either by directly inhibiting apoptosis of spermatogenic cells and degrading PDLIM1 or indirectly by suppressing intracellular stressors.
Herein, we developed an enantioselective addition of aliphatic aldehydes to 2-hydroxychalcone promoted by cooperative organocatalysts, giving access to hybrid flavonoids in excellent ...enantioselectivities. This reaction took advantage of cycloisomerization of 2-hydroxychalcone to form a transient flavylium under the irradiation of 24 W CFL, which was trapped by the
in situ
generated chiral enamine intermediate. The synergistic action of chiral phosphoric acid secured the excellent outcome of this reaction by ion-pairing with the transient flavylium.
Herein, we developed an enantioselective addition of aliphatic aldehydes to 2-hydroxychalcone promoted by cooperative organocatalysts, giving access to hybrid flavonoids in excellent enantioselectivities.
Mitochondrial dysfunction plays a principal role in hypoxia‐induced endothelial injury, which is involved in hypoxic pulmonary hypertension and ischemic cardiovascular diseases. Recent studies have ...identified mitochondria‐associated membranes (MAMs) that modulate mitochondrial function under a variety of pathophysiological conditions such as high‐fat diet‐mediated insulin resistance, hypoxia reoxygenation‐induced myocardial death, and hypoxia‐evoked vascular smooth muscle cell proliferation. However, the role of MAMs in hypoxia‐induced endothelial injury remains unclear. To explore this further, human umbilical vein endothelial cells and human pulmonary artery endothelial cells were exposed to hypoxia (1% O2) for 24 hours. An increase in MAM formation was uncovered by immunoblotting and immunofluorescence. Then, we performed small interfering RNA transfection targeted to MAM constitutive proteins and explored the biological effects. Knockdown of MAM constitutive proteins attenuated hypoxia‐induced elevation of mitochondrial Ca2+ and repressed mitochondrial impairment, leading to an increase in mitochondrial membrane potential and ATP production and a decline in reactive oxygen species. Then, we found that MAM disruption mitigated cell apoptosis and promoted cell survival. Next, other protective effects, such as those pertaining to the repression of inflammatory response and the promotion of NO synthesis, were investigated. With the disruption of MAMs under hypoxia, inflammatory molecule expression was repressed, and the eNOS‐NO pathway was enhanced. This study demonstrates that the disruption of MAMs might be of therapeutic value for treating endothelial injury under hypoxia, suggesting a novel strategy for preventing hypoxic pulmonary hypertension and ischemic injuries.
MAMs formation is increased in endothelial cells under hypoxia. Disruption of mitochondria‐associated membrane (MAM) restores mitochondrial function in Ca2+m, respiration, reactive oxygen species (ROS), and mitochondrial membrane potential. Thus, hypoxia‐induced inflammation and apoptosis are attenuated and nitric oxide synthesis is promoted.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A tandem asymmetric Michael-addition/cyclization of cyclic 1,3-dicarbonyl compounds to β,γ-unsaturated α-ketoesters catalyzed by chiral phosphoric acid is presented. This protocol provides a facile ...approach for the construction of enantioenriched 9-alkyl tetrahydroxanthenones, an ubiquitous framework found in a number of natural products and pharmaceutical molecules, in high yields with good to high enantioselectivities.
Acute lung injury (ALI) is characterized by non-cardiogenic diffuse alveolar damage and often leads to a lethal consequence, particularly when hypoxia coexists. The treatment of ALI remains a ...challenge: pulmonary inflammation and hypoxia both contribute to its onset and progression and no effective prevention approach is available. Here, we aimed to investigate the underlying mechanism of hypoxia interaction with inflammation in ALI and to evaluate hypoxia-inducible factor 1 alpha (HIF-1α)-the crucial modulator in hypoxia-as a potential therapeutic target against ALI. First, we developed a novel ALI rat model induced by a combined low-dose of lipopolysaccharides (LPS) with acute hypoxia. Second, we used gene microarray analysis to evaluate the inflammatory profiles of bronchi alveolar lavage fluid cells of ALI rats. Third, we employed an alveolar macrophage cell line, NR8383 as an
system together with a toll-like receptor 4 (TLR4) antagonist TAK-242, to verify our
findings from ALI animals. Finally, we tested the therapeutic effects of HIF-1α augmentation against inflammation and hypoxia in ALI. We demonstrated that (i) LPS upregulated inflammatory genes, tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6), in the alveolar macrophages of ALI rats, which were further enhanced when ALI combined with hypoxia; (ii) hypoxia exposure could further enhance the upregulation of alveolar macrophageal TLR4 that was noticed in LPS-induced inflammatory ALI, conversely, TLR4 antagonist TAK-242 could suppress the macrophageal expression of TLR4 and inflammatory cytokines, including TNF-α, IL-1β, and IL-6, suggesting that the TLR4 signaling pathway as a central link between inflammation and hypoxia in ALI; (iii) manipulation of HIF-1α
could suppress TLR4 expression induced by combined LPS and hypoxia,
suppressing promoter activity of the TLR4 gene; (iv) preconditioning augmentation of HIF-1α
by HIF hydroxylase inhibitor, DMOG excreted protection against inflammatory, and hypoxic processes in ALI. Together, we see that hypoxia can exacerbate inflammation in ALI
the activation of the TLR4 signaling pathway in alveolar macrophages and predispose impairment of the alveolar-capillary barrier in the development of ALI. Targeting HIF-1α can suppress TLR4 expression and macrophageal inflammation, suggesting the potential therapeutic and preventative value of HIF-1α/TLR4 crosstalk pathway in ALI.
High-altitude cerebral edema (HACE) is the severe type of acute mountain sickness (AMS) and life threatening. A subclinical inflammation has been speculated, but the exact mechanisms underlying the ...HACE are not fully understood.
Human volunteers ascended to high altitude (3860 m, 2 days), and rats were exposed to hypoxia in a hypobaric chamber (5000 m, 2 days). Human acute mountain sickness was evaluated by the Lake Louise Score (LLS), and plasma corticotrophin-releasing hormone (CRH) and cytokines TNF-α, IL-1β, and IL-6 were measured in rats and humans. Subsequently, rats were pre-treated with lipopolysaccharide (LPS, intraperitoneal (ip) 4 mg/kg, 11 h) to induce inflammation prior to 1 h hypoxia (7000 m elevation). TNF-α, IL-1β, IL-6, nitric oxide (NO), CRH, and aquaporin-4 (AQP4) and their gene expression, Evans blue, Na(+)-K(+)-ATPase activity, p65 translocation, and cell swelling were measured in brain by ELISA, Western blotting, Q-PCR, RT-PCR, immunohistochemistry, and transmission electron micrography. MAPKs, NF-κB pathway, and water permeability of primary astrocytes were demonstrated. All measurements were performed with or without LPS challenge. The release of NO, TNF-α, and IL-6 in cultured primary microglia by CRH stimulation with or without PDTC (NF-κB inhibitor) or CP154,526 (CRHR1 antagonist) were measured.
Hypobaric hypoxia enhanced plasma TNF-α, IL-1β, and IL-6 and CRH levels in human and rats, which positively correlated with AMS. A single LPS injection (ip, 4 mg/kg, 12 h) into rats increased TNF-α and IL-1β levels in the serum and cortex, and AQP4 and AQP4 mRNA expression in cortex and astrocytes, and astrocyte water permeability but did not cause brain edema. However, LPS treatment 11 h prior to 1 h hypoxia (elevation, 7000 m) challenge caused cerebral edema, which was associated with activation of NF-κB and MAPKs, hypoxia-reduced Na(+)-K(+)-ATPase activity and blood-brain barrier (BBB) disruption. Both LPS and CRH stimulated TNF-α, IL-6, and NO release in cultured rat microglia via NF-κB and cAMP/PKA.
Preexisting systemic inflammation plus a short severe hypoxia elicits cerebral edema through upregulated AQP4 and water permeability by TLR4 and CRH/CRHR1 signaling. This study revealed that both infection and hypoxia can cause inflammatory response in the brain. Systemic inflammation can facilitate onset of hypoxic cerebral edema through interaction of astrocyte and microglia by activation of TLR4 and CRH/CRHR1 signaling. Anti-inflammatory agents and CRHR1 antagonist may be useful for prevention and treatment of AMS and HACE.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
BACKGROUND:Although the mechanisms and pathways mediating ARDS have been studied extensively, less attention has been given to the mechanisms and pathways that counteract injury responses. This study ...found that the apelin-APJ pathway is an endogenous counterinjury mechanism that protects against ARDS. METHODS:Using a rat model of oleic acid (OA)-induced ARDS, the effects of ARDS on apelin and APJ receptor expressions and on APJ receptor binding capacity were examined. The protective effect of activating the apelin-APJ pathway against OA- or lipopolysaccharide (LPS)-induced ARDS was evaluated. RESULTS:ARDS was coupled to upregulations of the apelin and APJ receptor. Rats with OA-induced ARDS had higher lung tissue levels of apelin proprotein and APJ receptor expressions; elevated plasma, BAL fluid (BALF), and lung tissue levels of apelin-36 and apelin-12/13; and an increased apelin-APJ receptor binding capacity. Upregulation of the apelin-APJ system has important pathophysiologic function. Stimulation of the apelin-APJ signaling using receptor agonist apelin-13 alleviated, whereas inhibition of the apelin-APJ signaling using receptor antagonist Ala-apelin-13 exacerbated, OA-induced lung pathologies, extravascular lung water accumulation, capillary-alveolar leakage, and hypoxemia. The APJ receptor agonist inhibited, and the APJ receptor antagonist augmented, OA-induced lung tissue and BALF levels of tumor necrosis factor-α and monocyte chemoattractant protein-1, and plasma and lung tissue levels of malondialdehyde. Postinjury treatment with apelin-13 alleviated lung inflammation and injury and improved oxygenation in OA- and LPS-induced lung injury. CONCLUSIONS:The apelin-APJ signaling pathway is an endogenous anti-injury and organ-protective mechanism that is activated during ARDS to counteract the injury response and to prevent uncontrolled lung injury.
High-altitude polycythemia (HAPC) affects individuals living at high altitudes, characterized by increased red blood cells (RBCs) production in response to hypoxic conditions. The exact mechanisms ...behind HAPC are not fully understood. We utilized a mouse model exposed to hypobaric hypoxia (HH), replicating the environmental conditions experienced at 6000 m above sea level, coupled with in vitro analysis of primary splenic macrophages under 1% O
to investigate these mechanisms. Our findings indicate that HH significantly boosts erythropoiesis, leading to erythrocytosis and splenic changes, including initial contraction to splenomegaly over 14 days. A notable decrease in red pulp macrophages (RPMs) in the spleen, essential for RBCs processing, was observed, correlating with increased iron release and signs of ferroptosis. Prolonged exposure to hypoxia further exacerbated these effects, mirrored in human peripheral blood mononuclear cells. Single-cell sequencing showed a marked reduction in macrophage populations, affecting the spleen's ability to clear RBCs and contributing to splenomegaly. Our findings suggest splenic ferroptosis contributes to decreased RPMs, affecting erythrophagocytosis and potentially fostering continuous RBCs production in HAPC. These insights could guide the development of targeted therapies for HAPC, emphasizing the importance of splenic macrophages in disease pathology.
A bio-inspired synthesis of hybrid flavonoids from 2-hydroxylchalcone is described. Under the irradiation of 24 W CFL, 2-hydroxychalcone reacts with various nucleophiles to deliver structurally ...diverse hybrid flavonoids in good to excellent yields in the presence of a catalytic Brønsted acid. Moreover, moderate enantioselectivities could be obtained using a catalytic chiral phosphoric acid
via
counter anion directed addition. Based on mechanistic studies, the reaction is proposed to proceed
via
tandem double-bond isomerization/dehydrated cyclization of 2-hydroxychalcone to form a transient flavylium cation, which is
in situ
captured by nucleophiles to afford hybrid flavonoids.
An efficient protocol for the synthesis of hybrid flavonoids was achieved
via
a bio-inspired tandem reaction of 2-hydroxychalcone with various nucleophiles.
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IJS, KILJ, NUK, UL, UM, UPUK
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