Retinoic acid attenuates ischemic injury-induced activation of glial cells and inflammatory factors in a rat stroke model

Stroke is a leading cause of death and long-term disability which can cause oxidative damage and inflammation of the neuronal cells. Retinoic acid is an active metabolite of vitamin A that has various beneficial effects including antioxidant and anti-inflammatory effects. In this study, we investigated whether retinoic acid modulates oxidative stress and inflammatory factors in a stroke animal model. A middle cerebral artery occlusion (MCAO) was performed on adult male rats to induce focal cerebral ischemia. Retinoic acid (5 mg/kg) or vehicle was injected into the peritoneal cavity for four days before MCAO surgery. The neurobehavioral tests were carried out 24 h after MCAO and cerebral cortex tissues were collected. The cortical damage was assessed by hematoxylin-eosin staining and reactive oxygen species assay. In addition, Western blot and immunohistochemical staining were performed to investigate the activation of glial cells and inflammatory cytokines in MCAO animals. Ionized calcium-binding adapter molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP) were used as markers of microglial and astrocyte activation, respectively. Tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were used as representative pro-inflammatory cytokines. Results showed that MCAO damage caused neurobehavioral defects and histopathological changes in the ischemic region and increased oxidative stress. Retinoic acid treatment reduced these changes caused by MCAO damage. We detected increases in Iba-1 and GFAP in MCAO animals treated with vehicle. However, retinoic acid alleviated increases in Iba-1 and GFAP caused by MCAO damage. Moreover, MCAO increased levels of nuclear factor-κB and pro-inflammatory cytokines, including TNF-α and IL-1β. Retinoic acid alleviated the expression of these inflammatory proteins. These findings elucidate that retinoic acid regulates microglia and astrocyte activation and modulates pro-inflammatory cytokines. Therefore, this study suggests that retinoic acid exhibits strong antioxidant and anti-inflammatory properties by reducing oxidative stress, inhibiting neuroglia cell activation, and preventing the increase of pro-inflammatory cytokines in a cerebral ischemia.

Modulation of thioredoxin by chlorogenic acid in an ischemic stroke model and glutamate-exposed neurons

Ischemic stroke increases the production of reactive oxygen species (ROS), which can eventually lead to neuronal death. Thioredoxin is a small reductase protein that acts as an eliminator of ROS and protects neurons from brain damage. Chlorogenic acid is known as a phenolic compound that has a neuroprotective effect. We investigated the change of thioredoxin expression by chlorogenic acid in a middle cerebral artery occlusion (MCAO) animal model. Adult rats were injected intraperitoneally with phosphate buffered saline or chlorogenic acid (30 mg/kg) 2 h after MCAO. MCAO damage induced neurological defects and increased ROS and lipid peroxidation levels, however, chlorogenic acid mitigated these changes. MCAO damage reduced thioredoxin expression, which was mitigated by chlorogenic acid treatment. The interaction between thioredoxin and apoptosis signal-regulating kinase 1 (ASK1) was decreased in MCAO animals, chlorogenic acid treatment prevented this decrease. In cultured neurons, chlorogenic acid dose-dependently attenuated glutamate-induced decreases in cell viability and thioredoxin expression. Glutamate toxicity downregulated bcl-2 and upregulated bax, cytochrome c, and caspase-3, however, chlorogenic acid attenuated these changes. The mitigating effect of chlorogenic acid was lower in thioredoxin siRNA-transfected cells than in non-transfected cells. These results provide evidence that chlorogenic acid exerts potent antioxidant and neuroprotective effects through regulation of thioredoxin and modulation of ASK1 and thioredoxin binding in ischemic brain injury. These findings indicate that chlorogenic acid exerts a neuroprotective effect by regulating thioredoxin expression in cerebral ischemia and glutamate exposure conditions.

Epigallocatechin gallate improves neuronal damage in animal model of ischemic stroke and glutamate-exposed neurons via modulation of hippocalcin expression

Epigallocatechin gallate (EGCG) is a polyphenolic component of green tea that has anti-oxidative and anti-inflammatory effects in neurons. Ischemic stroke is a major neurological disease that causes irreversible brain disorders. It increases the intracellular calcium concentration and induces apoptosis. The regulation of intracellular calcium concentration is important to maintain the function of the nervous system. Hippocalcin is a neuronal calcium sensor protein that controls intracellular calcium concentration. We investigated whether EGCG treatment regulates the expression of hippocalcin in stroke animal model and glutamate-induced neuronal damage. We performed middle cerebral artery occlusion (MCAO) to induce cerebral ischemia. EGCG (50 mg/kg) or phosphate buffered saline was injected into the abdominal cavity just before MCAO surgery. The neurobehavioral tests were performed 24 h after MCAO surgery and cerebral cortex tissue was collected. MCAO damage induced severe neurobehavioral disorders, increased infarct volume, and decreased the expression of hippocalcin in the cerebral cortex. However, EGCG treatment improved these deficits and alleviated the decrease in hippocalcin expression in cerebral cortex. In addition, EGCG dose-dependently alleviated neuronal cell death and intracellular calcium overload in glutamate-exposed neurons. Glutamate exposure reduced hippocalcin expression, decreased Bcl-2 expression, and increased Bax expression. However, EGCG treatment mitigated these changes caused by glutamate toxicity. EGCG also attenuated the increase in caspase-3 and cleaved caspase-3 expressions caused by glutamate exposure. The effect of EGCG was more pronounced in non-transfected cells than in hippocalcin siRNA-transfected cells. These findings demonstrate that EGCG protects neurons against glutamate toxicity through the regulation of Bcl-2 family proteins and caspase-3. It is known that hippocalcin exerts anti-apoptotic effect through the modulation of apoptotic pathway. Thus, we can suggest evidence that EGCG has a neuroprotective effect by regulating hippocalcin expression in ischemic brain damage and glutamate-exposed cells.

Chlorogenic acid regulates the expression of protein phosphatase 2A subunit B in the cerebral cortex of a rat stroke model and glutamate-exposed neurons

BACKGROUND

Ischemic stroke is a serious neurological disorder caused by blockages in cerebral artery. Protein phosphatase 2A (PP2A) is a phosphatase that performs a critical role in cell signaling and growth. PP2A subunit B acts as a neuroprotective agent in the nerve system. Chlorogenic acid, which is mainly found in roasted coffee, has antioxidant, anti-inflammatory, and anti-apoptotic effects. We hypothesized that chlorogenic acid modulates PP2A subunit B expression in ischemic stroke models and glutamate-mediated neurons. Middle artery occlusion (MCAO) surgery was operated and chlorogenic acid (30 mg/kg) or phosphate buffer saline was treated 2 h after MCAO. The cerebral cortex was collected 24 h after surgery and the change of PP2A subunit B expression was analyzed. Glutamate and/or chlorogenic acid were treated in cultured neurons, further study was performed.

RESULTS

A decrease in PP2A subunit B expression in MCAO animals was identified. Chlorogenic acid alleviated this decrease due to ischemic injury. Moreover, the number of PP2A subunit B-positive cells in the ischemic cerebral cortex was significantly decreased, chlorogenic acid alleviated this decrease. We also found protective effects of chlorogenic acid in neurons exposed to glutamate. Glutamate decreased the expression of PP2A subunit B and chlorogenic acid mitigated this decrease. Our results elucidated that chlorogenic acid performs neuroprotective functions and attenuates the reduction of PP2A subunit B by brain damage and glutamate-mediated excitotoxicity.

CONCLUSIONS

We showed that chlorogenic acid attenuated the decrease of PP2A subunit B in ischemic injury and neurons exposed to glutamate. Since PP2A subunit B contributes to the protection of brain tissue, we can suggest that chlorogenic acid preserves neurons by modulating PP2A subunit B during ischemic damage.

Neuroprotective effects of chlorogenic acid by controlling the Bcl-2 family protein in a stroke animal model

Ischemic stroke causes severe brain damage and high mortality. Chlorogenic acid is a phenolic compound that has neuroprotective properties. B-cell lymphoma-2 (Bcl-2) family proteins are important for apoptosis regulation. Bcl-2 and Bcl-xL are proteins that inhibit apoptosis, and Bax and Bad induce apoptosis. In this study, we investigated whether chlorogenic acid exerts a neuroprotective effect against ischemic stroke damage by regulating Bcl-2 family proteins. We performed middle cerebral artery occlusion (MCAO) to induce ischemic stroke in adult male rats. The animals were intraperitoneally injected with normal saline as a vehicle or chlorogenic acid (30 mg/kg) 2 hr after MCAO. Cerebral cortex tissue was collected 24 hr after MCAO damage. MCAO damage caused histopathological changes and increased the number of terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick end labeling-positive cells, while chlorogenic acid attenuated these changes. RT-qPCR and Western blot results showed decreases in Bcl-2 and Bcl-xL expression and an increase in Bax and Bad expression in MCAO animals. However, chlorogenic acid treatment attenuated these changes due to MCAO damage. The interaction of Bax with Bcl-2 or Bcl-xL decreased in MCAO animals, and the binding of Bad with Bcl-2 or Bcl-xL increased. However, chlorogenic acid treatment reduced these changes. Chlorogenic acid also prevented MCAO-induced increases in caspase-3 and caspase-9 expression. This study provides evidence that chlorogenic acid has neuroprotective effects against MCAO damage by modulating Bcl-2 family proteins including Bcl-2, Bcl-xL, Bax, and Bad. Furthermore, chlorogenic acid regulates the interaction between Bcl-2 family proteins. In conclusion, chlorogenic acid contributes to neuroprotection against ischemic stroke damage by controlling Bcl-2 family proteins.

Retinoic Acid Has Neuroprotective effects by Modulating Thioredoxin in Ischemic Brain Damage and Glutamate-exposed Neurons

Ischemic stroke is a neurological disorder that causes pathological changes by increasing oxidative stress. Retinoic acid is one of the metabolites of vitamin A. It regulates oxidative stress and exerts neuroprotective effects. Thioredoxin is a small redox protein with antioxidant activity. The aim of this study was to investigate whether retinoic acid modulates the expression of thioredoxin in ischemic brain injury. Cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) surgery and retinoic acid (5 mg/kg) or vehicle was administered to adult male rats for four days prior to surgery. MCAO induced neurological deficits and increased oxidative stress and retinoic acid attenuated these changes. Retinoic acid ameliorated the MCAO-induced decrease in thioredoxin expression. MCAO decreases the interaction between thioredoxin and apoptosis signal-regulating kinase 1 (ASK1), and retinoic acid treatment alleviates this decrease. Glutamate (5 mM) exposure induced cell death and decreased thioredoxin expression in cultured neurons. Retinoic acid treatment attenuated these changes in a dose-dependent manner. Retinoic acid prevented the decrease of bcl-2 expression and the increase of bax expression caused by glutamate exposure. Moreover, retinoic acid attenuated the increases in caspase-3, cleaved caspase-3, and cytochrome c in glutamate-exposed neurons. However, the mitigation effects of retinoic acid were lower in thioredoxin siRNA-transfected neurons than in non-transfected neurons. These results demonstrate that retinoic acid regulates oxidative stress and thioredoxin expression, maintains the interaction between thioredoxin and ASK1, and modulates apoptosis-associated proteins. Taken together, these results suggest that retinoic acid has neuroprotective effects by regulating thioredoxin expression and modulating apoptotic pathway.

Identification of proteins regulated by chlorogenic acid in an ischemic animal model: a proteomic approach

BACKGROUND

Cerebral ischemia is a serious neurological disorder that can lead to high morbidity and mortality. Chlorogenic acid is a polyphenol compound with antioxidant that can regulate proteins in cerebral ischemia. Middle cerebral artery occlusion (MCAO) surgery was performed to induce ischemic brain injury and was maintained for 24 h. Chlorogenic acid (30 mg/kg) or vehicle was administrated into the peritoneal cavity 2 h after MCAO surgery. The cerebral cortical tissues were collected for further study and a proteomic approach was performed to identify the proteins changed by chlorogenic acid in the MCAO animals.

RESULTS

We found that chlorogenic acid alleviated in changes in adenosylhomocysteinase, glycerol-3-phosphate dehydrogenase, eukaryotic translation initiation factor 4A-II, apolipoprotein A-I, and mu-crystallin. These proteins were reduced in MCAO animals with vehicle, and these reductions were attenuated by chlorogenic acid treatment. The mitigation of this reduction by chlorogenic acid was confirmed by the reverse transcription PCR technique. These proteins are associated with energy metabolism, protein synthesis, inflammation, and physiological metabolism. They are involved in the neuroprotective effect of chlorogenic acid. These results showed that chlorogenic acid alleviates the neurological disorders caused by MCAO and regulates the expression of proteins involved in neuroprotection.

CONCLUSIONS

Therefore, our findings provide evidence that chlorogenic acid plays a neuroprotective role in stroke animal models by controlling specific proteins.

[Regulation of colony-stimulating factor 1 receptor inhibitor pexidartinib on the senescence of mouse bone marrow-derived macrophages stimulated by lipopolysaccharide]

Objective: To investigate the effects of colony-stimulating factor 1 receptor (CSF-1R) inhibitor pexidartinib (PLX3397) on the senescence of bone marrow-derived macrophages (BMDM) stimulated by lipopolysaccharide (LPS). Methods: BMDM were isolated and cultured from femurs and tibiae of 10 male C57BL/6 mice aged 6-8 weeks (obtained from Laboratory Animal Center of Guizhou Medical University). They were divided into blank control group, LPS group (treated with 1 μg/ml LPS for 24 h) as well as low, medium and high concentration PLX3397 pretreatment groups (treated with 100, 500 and 1 000 nmol/L PLX3397 for 4 h respectively followed by 1 μg/ml LPS for 24 h). The corresponding markers of macrophages were detected by flow cytometry. Cell viability was detected by cell counting kit-8 and cellular senescence was detected by senescence-associated-β-galactosidase (SA-β-gal) staining. Meanwhile, protein expressions of cycle-dependent kinase inhibitor p16, p21 and CSF-1R were detected by Western blotting, and the expressions of p16 and p21 were detected by intracellular immunofluorescence. Real-time fluorescence quantitative PCR (RT-qPCR) was used to investigate the mRNA levels of senescence-associated secretory phenotype (SASP) genes including interleukin (IL), IL-1β, chemokine-1/10 (CXCL-1/10), matrix metalloproteinase-8 (MMP-8), and transforming growth factor-β (TGF-β). Results: The rate of SA-β-gal positive staining in medium and high concentration PLX3397 pretreatment groups [(39.33±4.93)% and (36.33±3.06)% respectively] were significantly downregulated compared with LPS group [(52.00±3.00)%] (P=0.020, P=0.005). The expression of CSF-1R protein in low, medium and high concentration PLX3397 pretreatment groups were (0.74±0.18, 0.61±0.07, 0.54±0.06), all of which were significantly lower than that in LPS group (1.16±0.08) (P=0.013, P=0.002, P<0.001). The expression levels of CSF-1R mRNA in low, medium and high concentration PLX3397 pretreatment groups (1.04±0.06, 0.90±0.05, 1.18±0.08) showed similar trend (2.90±0.25) (P<0.001). The average fluorescence intensity of p16 in all PLX3397 pretreatment groups were 49.76±3.65, 48.21±1.72, 47.99±1.26 respectively, which were significantly lower than that in LPS group (66.88±5.85) (P=0.001, P<0.001, P<0.001). The average fluorescence intensity of p21 in medium and high concentration PLX3397 pretreatment groups were (34.43±3.62, 30.13±0.86), significantly lower than that in LPS group (46.82±5.33) (P=0.043, P=0.007). The expression of p16 protein in low, medium and high concentration PLX3397 pretreatment groups (0.56±0.04, 0.55±0.04, 0.35±0.19) were significantly lower than that in LPS group (0.98±0.10) (P=0.003, P=0.002, P<0.001), as well the expression of p21 protein (0.69±0.20, 0.42±0.08, 0.26±0.14) (P=0.032, P=0.002, P<0.001). According to the results of RT-qPCR, the expressions of IL-6, IL-1β, CXCL-1, CXCL-10 and MMP-8 in PLX3397 pretreatment groups were significantly lower than those in LPS group (P<0.001), while the expression of TGF-β increased (P<0.001). Conclusions: LPS could induce the cell senescence, increase the secretion of SASP and aggravate local inflammation by activating the CSF-1R on the cell surface of bone marrow-derived macrophages. CSF-1R inhibitor PLX3397 might attenuate CSF-1R activation associated with LPS and inhibit the senescence of bone marrow-derived macrophages induced by LPS.

Epigallocatechin gallate restores the reduction of protein phosphatase 2 A subunit B caused by middle cerebral artery occlusion

BACKGROUND

Epigallocatechin gallate (EGCG) is a flavonoid compound commonly found in green tea. It exhibits antioxidant, anti-inflammatory, and neuroprotective effects in cerebral ischemia. Protein phosphatase 2 A (PP2A) is an important serine/threonine phosphatase enzyme involved in various cellular activities. PP2A subunit B is present abundantly in the brain and plays an important role in the nervous system. We investigated the effect of EGCG on the expression level of PP2A subunit B in cerebral ischemia caused by middle cerebral artery occlusion (MCAO). EGCG (50 mg/kg) or vehicle was injected into the peritoneal cavity prior to MCAO surgery. Neurological behavior tests were performed 24 h after MCAO, and right cerebral cortex tissue was collected. Cerebral ischemia caused serious neurological abnormalities, which were alleviated by EGCG administration. We screened the expression of PP2A subunits containing A, B, and C using reverse-transcription PCR. We confirmed that PP2A subunit B exhibited significant changes in MCAO animals compared to subunits A and C. We continuously examined the expression of PP2A subunit B protein in MCAO animals using Western blot analysis.

RESULTS

EGCG alleviated the reduction of PP2A subunit B protein by MCAO damage. In addition, immunohistochemistry demonstrated a decrease in the number of PP2A subunit B-positive cells in the cerebral cortex, and EGCG attenuated this decrease. Maintenance of PP2A subunit B is important for normal brain function.

CONCLUSION

Therefore, our findings suggest that EGCG exerts neuroprotective effects against cerebral ischemia through modulation of PP2A subunit B expression.

Chlorogenic acid modulates the ubiquitin-proteasome system in stroke animal model

BACKGROUND

Chlorogenic acid, a phenolic compound, has potent antioxidant and neuroprotective properties. The ubiquitin-proteasome system is an important regulators of neurodevelopment and modulators of neuronal function. This system is associated with neurodevelopment and neurotransmission through degradation and removal of damaged proteins. Activation of the ubiquitin-proteasome system is a critical factor in preventing cell death. We have previously reported a decrease in the activity of the ubiquitin-proteasome system during cerebral ischemia. This study investigated whether chlorogenic acid regulates the ubiquitin-proteasome system in an animal stroke model. In adult rats, middle cerebral artery occlusion (MCAO) surgery was performed to induce focal cerebral ischemia. Chlorogenic acid (30 mg/kg) or normal saline was injected into the abdominal cavity 2 h after MCAO surgery, and cerebral cortex tissues were collected 24 h after MCAO damage.

RESULTS

Chlorogenic acid attenuated neurobehavioral disorders and histopathological changes caused by MCAO damage. We identified the decreases in ubiquitin C-terminal hydrolase L1, ubiquitin thioesterase OTUB1, proteasome subunit α type 1, proteasome subunit α type 3, and proteasome subunit β type 4 expression using a proteomics approach in MCAO animals. The decrease in these proteins was alleviated by chlorogenic acid. In addition, the results of reverse transcription-polymerase chain reaction confirmed these changes. The identified proteins were markedly reduced in MCAO damage, while chlorogenic acid prevented these reductions induced by MCAO. The decrease of ubiquitin-proteasome system proteins in ischemic damage was associated with neuronal apoptosis.

CONCLUSIONS

Our results showed that chlorogenic acid regulates ubiquitin-proteasome system proteins and protects cortical neurons from neuronal damage. These results provide evidence that chlorogenic acid has neuroprotective effects and maintains the ubiquitin-proteasome system in ischemic brain injury.

Chlorogenic acid alleviates the reduction of Akt and Bad phosphorylation and of phospho-Bad and 14-3-3 binding in an animal model of stroke

BACKGROUND

Stroke is caused by disruption of blood supply and results in permanent disabilities as well as death. Chlorogenic acid is a phenolic compound found in various fruits and coffee and exerts antioxidant, anti-inflammatory, and anti-apoptotic effects.

OBJECTIVES

The purpose of this study was to investigate whether chlorogenic acid regulates the PI3K-Akt-Bad signaling pathway in middle cerebral artery occlusion (MCAO)-induced damage.

METHODS

Chlorogenic acid (30 mg/kg) or vehicle was administered peritoneally to adult male rats 2 h after MCAO surgery, and animals were sacrificed 24 h after MCAO surgery. Neurobehavioral tests were performed, and brain tissues were isolated. The cerebral cortex was collected for Western blot and immunoprecipitation analyses.

RESULTS

MCAO damage caused severe neurobehavioral disorders and chlorogenic acid improved the neurological disorders. Chlorogenic acid alleviated the MCAO-induced histopathological changes and decreased the number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells. Furthermore, MCAO-induced damage reduced the expression of phospho-PDK1, phospho-Akt, and phospho-Bad, which was alleviated with administration of chlorogenic acid. The interaction between phospho-Bad and 14-3-3 levels was reduced in MCAO animals, which was attenuated by chlorogenic acid treatment. In addition, chlorogenic acid alleviated the increase of cytochrome c and caspase-3 expression caused by MCAO damage.

CONCLUSIONS

The results of the present study showed that chlorogenic acid activates phospho-Akt and phospho-Bad and promotes the interaction between phospho-Bad and 14-3-3 during MCAO damage. In conclusion, chlorogenic acid exerts neuroprotective effects by activating the Akt-Bad signaling pathway and maintaining the interaction between phospho-Bad and 14-3-3 in ischemic stroke model.

Retinoic acid regulates the ubiquitin-proteasome system in a middle cerebral artery occlusion animal model

Background

Retinoic acid is a major metabolite of vitamin A and exerts beneficial effects including anti-oxidant and anti-inflammatory activities in neurons. The ubiquitin–proteasome system is an important biological system that regulates cell survival. Ubiquitination regulates protein degradation and plays an important role in oxidative stress. Deubiquitinating enzymes cleave ubiquitin from proteins and control ubiquitination-induced degradation. We detected decreases in ubiquitin carboxy-terminal hydrolase L1, ubiquitin thioesterase OTUB1, and proteasome subunit alpha types 1 and 3 in cerebral ischemic damage. In this study, we investigated whether retinoic acid regulates the expression of deubiquitinating enzymes ubiquitin carboxy-terminal hydrolase L1, ubiquitin thioesterase OTUB1, and proteasome subunit alpha types 1 and 3 in cerebral ischemic injury. Right middle cerebral artery occlusion (MCAO) was performed to induce cerebral ischemic damage in male rats. Retinoic acid (5 mg/kg) or vehicle was intraperitoneally injected every day from 4 days before surgery. Neurological behavioral tests were performed 24 h after MCAO, and right cerebral cortical tissues were collected.

Results

MCAO damage caused neurological behavioral dysfunction, and retinoic acid alleviated these deficits. The identified proteins decreased in MCAO animals with vehicle, while retinoic acid treatment attenuated these decreases. The results of proteomic study were confirmed by a reverse transcription-PCR technique. Expressions of ubiquitin carboxy-terminal hydrolase L1, ubiquitin thioesterase OTUB1, and proteasome subunit alpha types 1 and 3 were decreased in MCAO animals treated with vehicle. Retinoic acid treatment alleviated these MCAO-induced reductions. The ubiquitin–proteasome system plays an essential role in maintaining cell function and preserving cell shape against ischemic damage.

Conclusions

These findings suggest that retinoic acid regulates ubiquitin- and proteasome-related proteins including ubiquitin carboxy-terminal hydrolase L1, ubiquitin thioesterase OTUB1, and proteasome subunit alpha types 1 and 3 in a brain ischemia model. Changes in these proteins are involved in the neuroprotective effects of retinoic acid.

Quercetin ameliorates glutamate toxicity-induced neuronal cell death by controlling calcium-binding protein parvalbumin

Background

Glutamate is the main excitatory neurotransmitter. Excessive glutamate causes excitatory toxicity and increases intracellular calcium, leading to neuronal death. Parvalbumin is a calcium-binding protein that regulates calcium homeostasis. Quercetin is a polyphenol found in plant and has neuroprotective effects against neurodegenerative diseases.

Objectives

We investigated whether quercetin regulates apoptosis by modulating parvalbumin expression in glutamate induced neuronal damage.

Methods

Glutamate was treated in hippocampal-derived cell line, and quercetin or vehicle was treated 1 h before glutamate exposure. Cells were collected for experimental procedure 24 h after glutamate treatment and intracellular calcium concentration and parvalbumin expression were examined. Parvalbumin small interfering RNA (siRNA) transfection was performed to detect the relation between parvalbumin and apoptosis.

Results

Glutamate reduced cell viability and increased intracellular calcium concentration, while quercetin preserved calcium concentration and neuronal damage. Moreover, glutamate reduced parvalbumin expression and quercetin alleviated this reduction. Glutamate increased caspase-3 expression, and quercetin attenuated this increase in both parvalbumin siRNA transfected and non-transfected cells. The alleviative effect of quercetin was statistically significant in non-transfected cells. Moreover, glutamate decreased bcl-2 and increased bax expressions, while quercetin alleviated these changes. The alleviative effect of quercetin in bcl-2 family protein expression was more remarkable in non-transfected cells.

Conclusions

These results demonstrate that parvalbumin contributes to the maintainace of intracellular calcium concentration and the prevention of apoptosis, and quercetin modulates parvalbumin expression in glutamate-exposed cells. Thus, these findings suggest that quercetin performs neuroprotective function against glutamate toxicity by regulating parvalbumin expression.

[Pathogen distribution and antimicrobial resistance among lower respiratory tract infections in patients with hematological malignancies]

Objective: To investigate the pathogen distribution and antimicrobial resistance among lower respiratory tract infections in patients with hematological malignancies. Methods: Sputum samples were collected from 967 patients with hematological malignancies and lower respiratory tract infections in Department of Hematology,the Second Hospital of Shanxi Medical University from January 2017 to July 2020. The pathogens and drug sensitivity reports were carried out by automatic bacterial identification instruments. WHONET 5.6 and SPSS 20.0 softwares were used for statistical analysis. Results: A total of 961 strains of pathogens were isolated, 516 (53.7%) pathogens were Gram-negative bacteria, mainly 118 strains of Klebsiella pneumonia (12.3%), 68 strains of Pseudomonas aeruginosa (7.1%), 67 strains of Acinetobacter baumannii (7.0%),52 strains of Stenotrophomonas maltophilia (5.4%), 43 strains of Escherichia coli (4.5%), and 42 strains of Enterbacter cloacae (4.4%). There were 171 (17.8%) strains of Gram-positive bacteria and 274 (28.5%) fungi. The drug resistance rates of Pseudomonas aeruginosa and Acinetobacter baumannii to carbapenem were 22.1%-31.3%. Stenotrophomonas maltophilia was sensitive to levofloxacin, compound sulfamethoxazole and minocycline. The antimicrobial resistance rates of these three enterobacteria to carbapenems, cefoperazone/sulbactam, piperacillin/tazobactam were low (<10%). The resistant Gram-positive bacteria to ticoplanin, vancomycin and linazolamide were not detected. Conclusion: The major pathogens related to lower respiratory tract infections in patients with hematological malignancies are gram-negative bacteria in our centre. Different pathogens appear different characteristics of antimicrobial resistance.

Retinoic acid exerts neuroprotective effects against focal cerebral ischemia by preventing apoptotic cell death

Cerebral ischemia is a neurological disorder that leads to cognitive decline and high mortality. Retinoic acid is a metabolite of vitamin A that has anti-inflammatory and anti-apoptotic effects. This study investigated whether retinoic acid prevents neuronal cell damage on focal cerebral ischemia through modulating apoptosis signaling pathway. Middle cerebral artery occlusion (MCAO) was performed to induce focal cerebral ischemia in adult male rats. Retinoic acid (5 mg/kg) or vehicle was injected intraperitoneally for 4 days prior to MCAO. Neurological behavior deficit tests were performed 24 h after MCAO. Brain edema and infarct volume were measured, and TUNEL histochemistry was carried out. We also investigated the changes in apoptosis-related proteins including bcl-2 family proteins and caspases. MCAO injury induced severe neurological behavior deficits and brain edema. It also increased infarct volume, histopathological damages, and the number of TUNEL-positive cells in cerebral cortex. However, retinoic acid pretreatment attenuated MCAO-induced neurological behavior deficits, brain edema, and infarction. It also alleviated histopathological lesion and decreased the number of TUNEL-positive cells. Bcl-2 and bax proteins are representative bcl-2 family proteins. MCAO injury induced a decrease in bcl-2 expression and an increase in bax expression, and retinoic acid pretreatment alleviated these changes. MCAO injury caused a decrease in bcl-2/bax expression ratio in cerebral cortex, while retinoic acid restored this decrease by MCAO. Moreover, our result showed increases in caspase-9, caspase-3, PARP protein levels in MCAO-operated animals. Retinoic acid pretreatment prevented these increases. We identified the changes in cleaved forms of these proteins, similar to the changes in full-length protein. Activation of caspases and PARP proteins are considered to be representative apoptosis indicators. This study showed that retinoic acid regulates bcl-2 family proteins and caspase proteins in focal cerebral ischemia. Thus, our findings demonstrate that retinoic acid exhibits a neuroprotective effect against ischemic damage by modulating apoptosis signaling pathway.

Quercetin attenuates the reduction of parvalbumin in middle cerebral artery occlusion animal model

Background

Calcium is a critical factor involved in modulation of essential cellular functions. Parvalbumin is a calcium buffering protein that regulates intracellular calcium concentrations. It prevents rises in calcium concentrations and inhibits apoptotic processes during ischemic injury. Quercetin exerts potent antioxidant and anti-apoptotic effects during brain ischemia. We investigated whether quercetin can regulate parvalbumin expression in cerebral ischemia and glutamate toxicity-induced neuronal cell death. Adult male rats were treated with vehicle or quercetin (10 mg/kg) 30 min prior to middle cerebral artery occlusion (MCAO) and cerebral cortical tissues were collected 24 h after MCAO. We used various techniques including Western blot, reverse transcription-PCR, and immunohistochemical staining to elucidate the changes of parvalbumin expression.

Results

Quercetin ameliorated MCAO-induced neurological deficits and behavioral changes. Moreover, quercetin prevented MCAO-induced a decrease in parvalbumin expression.

Conclusions

These findings suggest that quercetin exerts a neuroprotective effect through regulation of parvalbumin expression.

Decrease of protein phosphatase 2A subunit B by glutamate exposure in the cerebral cortex of neonatal rats

Glutamate induces neurotoxicity during brain development, causing nerve damage. Protein phosphatase 2A (PP2A) is a type of serine/threonine phosphatase that regulates various biological functions. Among the PP2A subunit types, subunit B is abundant in brain tissue and plays an essential role in the nervous system. This study investigated changes in PP2A subunit B expression through glutamate exposure in the cerebral cortex of newborn rats. Sprague-Dawley rat pups (7 days after birth) were injected intraperitoneally with vehicle or glutamate (10 mg/kg). After 4 h of drug treatment, the brain tissue was isolated and fixed for morphological study. In addition, the cerebral cortex was collected for RNA and protein works. We observed severe histopathological changes including swollen neuron and atrophied dendrite in the glutamate exposed cerebral cortex. Glutamate exposure leads to a decrease in PP2A subunit B. Reverse-transcription PCR and Western blot analyses confirmed that glutamate induces a decrease of PP2A subunit B in the cerebral cortex of newborn rats. Moreover, immunohistochemical study showed a decrease in PP2A subunit B positive cells. The reduction of PP2A subunit B expression is considered an indicator of neurodegenerative damage. These results suggest that glutamate exposure causes neuronal damage in the cerebral cortex of new born rats through a decrease in PP2A subunit B.

Baicalin alleviates lipopolysaccharide-induced neuroglial activation and inflammatory factors activation in hippocampus of adult mice

Baicalin is a natural flavonoid that exerts a variety of pharmaceutical effects such as anti-inflammatory and antioxidant. Lipopolysaccharide (LPS) is an endotoxin that releases inflammatory cytokines and induces inflammatory response. This study was investigated the anti-inflammatory mechanism of baicalin against LPS-induced inflammatory response in the hippocampus. Adult mice were randomly grouped into control, LPS-treated, and LPS and baicalin co-treated animals. LPS (250 μg/kg/day) and baicalin (10 mg/kg/day) were administered intraperitoneally for 7 consecutive days. We measured neuroglia cells activation and inflammatory factors activation using Western blot analysis and immunofluorescence staining techniques. Ionized calcium binding adaptor molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP) are widely used as microglia and astrocyte markers, respectively. LPS treatment increased Iba-1 and GFAP expression, while baicalin co-treatment attenuated this overexpression. Nuclear factor-kappa B (NF-κB) is a key mediator of inflammation. Baicalin co-treatment alleviated LPS-induced increase of NF-κB in the hippocampus. In addition, LPS treatment upregulated pro-inflammatory cytokines including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). However, baicalin co-treatment prevented LPS-induced increases of IL-1β and TNF-α in the hippocampus. Results from the present study showed that baicalin suppresses LPS-induced neuroinflammation by regulating microglia and astrocyte activation and modulating inflammatory factors in the hippocampus. Thus, these results demonstrate that baicalin has neuroprotective effect by alleviates microglia and astrocyte activation and modulates inflammatory response by suppressing NF-κB expression in hippocampus with neuroinflammation caused by LPS.

Decrease of 14-3-3 proteins by glutamate exposure in the cerebral cortex of newborn rats

Glutamate is a representative excitatory neurotransmitter. However, excessive glutamate exposure causes neuronal cell damage by generating neuronal excitotoxicity. Excitotoxicity in neonates caused by glutamate treatment induces neurological deficits in adults. The 14-3-3 family proteins are conserved proteins that are expressed ubiquitously in a variety of tissues. These proteins contribute to cellular processes, including signal transduction, protein synthesis, and cell cycle control. We proposed that glutamate induces neuronal cell damage by regulating 14-3-3 protein expression in newborn animals. In this study, we investigated the histopathological changes and 14-3-3 proteins expressions as a result of glutamate exposure in the neonatal cerebral cortex. Rat pups at post-natal day 7 were intraperitoneally administrated with vehicle or glutamate (10 mg/kg). Animals were sacrificed 4 h after treatment, and brain tissues were fixed for histological study. Cerebral cortices were isolated and frozen for proteomic study. We observed serious histopathological damages including shrunken dendrites and atypical neurons in glutamate-treated cerebral cortices. In addition, we identified that 14-3-3 family proteins decreased in glutamate-exposed cerebral cortices using a proteomic approach. Moreover, Western blot analysis provided results that glutamate treatment in neonates decreased 14-3-3 family proteins expressions, including the β/α, ζ/δ, γ, ε, τ, and η isoforms. 14-3-3 proteins are involved in signal transduction, metabolism, and anti-apoptotic functions. Thus, our findings suggest that glutamate induces neonatal neuronal cell damage by modulating 14-3-3 protein expression.

Epigallocatechin gallate alleviates neuronal cell damage against focal cerebral ischemia in rats

Cerebral ischemia is a neurological disorder that causes permanent disability and is sometimes fatal. Epigallocatechin gallate (EGCG) is a natural polyphenol that exerts beneficial antioxidant and anti-inflammatory effects. The aim of this study was to investigate the neuroprotective effects of EGCG against cerebral ischemia. Middle cerebral artery occlusion was surgically initiated to induce focal cerebral ischemia in adult male rats. EGCG (50 mg/kg) or vehicle was intraperitoneally injected just prior to middle cerebral artery occlusion (MCAO) induction. Neuronal behavior tests were performed 24 hr after MCAO. Brain tissues were isolated to evaluate infarct volume, histological changes, apoptotic cell death, and caspase-3 and poly ADP-ribose polymerase (PARP) levels. MCAO injury led to serious functional neurological deficits and increased infarct volume. Moreover, it induced histopathological lesions and increased the numbers of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cells in the cerebral cortex. However, EGCG improved MCAO-induced neurological deficits and reduced infarct volume, alleviated histopathological changes, and decreased TUNEL-positive cells in the cerebral cortex of MCAO rats. Western blot analysis showed increases of caspase-3 and PARP expression levels in MCAO rats with vehicle, whereas EGCG administration alleviated these increases after MCAO injury. These results demonstrate that EGCG exerts a neuroprotective effect by regulating caspase-3 and PARP proteins during cerebral ischemia. In conclusion, we suggest that EGCG acts as a potent neuroprotective agent by modulating the apoptotic signaling pathway.

Quercetin Reduces Ischemic Brain Injury by Preventing Ischemia-induced Decreases in the Neuronal Calcium Sensor Protein Hippocalcin

Calcium acts as a second messenger that mediates physiologic functions, such as metabolism, cell proliferation, and apoptosis. Hippocalcin is a neuronal calcium sensor protein that regulates intracellular calcium concentration. Moreover, it prevents neuronal cell death from oxidative stress. Quercetin has excellent antioxidant properties and preventative effects. We studied modulation of hippocalcin expression by quercetin treatment in cerebral ischemic injury and glutamate-induced neuronal cell damage. Focal cerebral ischemia was induced by permanent middle cerebral artery occlusion (pMCAO). Male Sprague-Dawley rats were injected with vehicle or quercetin (10 mg/kg) 1 h prior to pMCAO, and cerebral cortical tissues were isolated 24 h after pMCAO. Quercetin improved pMCAO-induced neuronal movement deficit and infarction. pMCAO induced a decrease in hippocalcin expression in the cerebral cortex. However, quercetin treatment attenuated this pMCAO-induced decrease. In cultured hippocampal cells, glutamate excitotoxicity dramatically increased the intracellular calcium concentration, whereas quercetin alleviated intracellular calcium overload. Moreover, Western blot and immunocytochemical studies showed reduction of hippocalcin expression in glutamate-exposed cells. Quercetin prevented this glutamate-induced decrease. Furthermore, caspase-3 expression in hippocalcin siRNA transfection conditions is higher than caspase-3 expression in un-transfection conditions. Quercetin treatment attenuated the increase of caspase-3. Taken together, these results suggest that quercetin exerts a preventative effect through attenuation of intracellular calcium overload and restoration of down-regulated hippocalcin expression during ischemic injury.

Quercetin Attenuates Decrease of Thioredoxin Expression Following Focal Cerebral Ischemia and Glutamate-induced Neuronal Cell Damage

Quercetin is a bioactive flavonoid which abundantly exists in vegetables and fruits. Quercetin exerts a neuroprotective effect against cerebral ischemia. Thioredoxin acts as antioxidant by regulating redox signaling. This study investigated whether quercetin regulates thioredoxin expression in focal cerebral ischemia and glutamate-induced neuronal cell death. Male Sprague Dawley rats (210-230 g) were intraperitoneally injected with vehicle or quercetin (10 mg/kg) 1 h prior to middle cerebral artery occlusion (MCAO). Cerebral cortex was collected 24 h after MCAO. MCAO led to neurological movement deficits, brain edema, and serious histopathological damages in cerebral cortex, and quercetin alleviated these damages following MCAO. We observed the change of thioredoxin expression in MCAO animals with quercetin using proteomic approach, reverse-transcription PCR, and Western blot analyses. Thioredoxin expression decreased in vehicle-treated MCAO animals, while quercetin attenuated this decrease. Moreover, quercetin treatment alleviated the decrease in the number of thioredoxin-positive cells in cerebral cortex of MCAO animals. Furthermore, immunoprecipitation analysis demonstrated that interaction of apoptosis signal-regulating kinase 1 (ASK1) and thioredoxin was decreased in MCAO animals with vehicle, while quercetin prevented MCAO-induced decrease in these binding. In addition, quercetin also alleviated the reduction of cell viability and the decrease in thioredoxin expression in glutamate-treated hippocampal cell line and primary cultures of cortical neurons. However in thioredoxin-silenced cortical neuron, anti-apoptotic effect of quercetin was decreased. Thus, changes of thioredoxin expression by quercetin may contribute to the neuroprotective effect of quercetin in focal cerebral ischemia. Our findings suggest that quercetin mediates its neuroprotective function by regulation of thioredoxin expression and maintenance of interaction between ASK1 and thioredoxin.

Identification of proteins differentially expressed by glutamate treatment in cerebral cortex of neonatal rats

Glutamate leads to neuronal cell damage by generating neurotoxicity during brain development. The objective of this study is to identify proteins that differently expressed by glutamate treatment in neonatal cerebral cortex. Sprague-Dawley rat pups (post-natal day 7) were intraperitoneally injected with vehicle or glutamate (10 mg/kg). Brain tissues were isolated 4 h after drug treatment and fixed for morphological study. Moreover, cerebral cortices were collected for protein study. Two-dimensional gel electrophoresis and mass spectrometry were carried out to identify specific proteins. We observed severe histopathological changes in glutamate-exposed cerebral cortex. We identified various proteins that differentially expressed by glutamate exposure. Identified proteins were thioredoxin, peroxiredoxin 5, ubiquitin carboxy-terminal hydrolase L1, proteasome subunit alpha proteins, isocitrate dehydrogenase, and heat shock protein 60. Heat shock protein 60 was increased in glutamate exposed condition. However, other proteins were decreased in glutamate-treated animals. These proteins are related to anti-oxidant, protein degradation, metabolism, signal transduction, and anti-apoptotic function. Thus, our findings can suggest that glutamate leads to neonatal cerebral cortex damage by regulation of specific proteins that mediated with various functions.

Lipopolysaccharide induces neuroglia activation and NF-κB activation in cerebral cortex of adult mice

Lipopolysaccharide (LPS) acts as an endotoxin, releases inflammatory cytokines, and promotes an inflammatory response in various tissues. This study investigated whether LPS modulates neuroglia activation and nuclear factor kappa B (NF-κB)-mediated inflammatory factors in the cerebral cortex. Adult male mice were divided into control animals and LPS-treated animals. The mice received LPS (250 μg/kg) or vehicle via an intraperitoneal injection for 5 days. We confirmed a reduction of body weight in LPS-treated animals and observed severe histopathological changes in the cerebral cortex. Moreover, we elucidated increases of reactive oxygen species and oxidative stress levels in LPS-treated animals. LPS administration led to increases of ionized calcium-binding adaptor molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP) expression. Iba-1 and GFAP are well accepted as markers of activated microglia and astrocytes, respectively. Moreover, LPS exposure induced increases of NF-κB and pro-inflammatory factors, such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). Increases of these inflammatory mediators by LPS exposure indicate that LPS leads to inflammatory responses and tissue damage. These results demonstrated that LPS activates neuroglial cells and increases NF-κB-mediated inflammatory factors in the cerebral cortex. Thus, these findings suggest that LPS induces neurotoxicity by increasing oxidative stress and activating neuroglia and inflammatory factors in the cerebral cortex.

Resveratrol modulates the Akt/GSK-3β signaling pathway in a middle cerebral artery occlusion animal model

Cerebral ischemia is a major cause of neurodegenerative disease. It induces neuronal vulnerability and susceptibility, and leads to neuronal cell death. Resveratrol is a polyphenolic compound that acts as an anti-oxidant. It exerts a neuroprotective effect against focal cerebral ischemic injury. Akt signaling pathway is accepted as a representative cell survival pathway, including proliferation, growth, and glycogen synthesis. This study investigated whether resveratrol regulates Akt/glycogen synthase kinase-3β (GSK-3β) pathway in a middle cerebral artery occlusion (MCAO)-induced ischemic brain injury. Adult male rats were intraperitoneally injected with vehicle or resveratrol (30 mg/kg) and cerebral cortices were isolated 24 h after MCAO. Neurological behavior test, corner test, brain edema measurment, and 2,3,5-triphenyltetrazolium chloride staining were performed to elucidate the neuroprotective effects of resveratrol. Phospho-Akt and phospho-GSK-3β expression levels were measured using Western blot analysis. MCAO injury led to severe neurobehavioral deficit, infraction, and histopathological changes in cerebral cortex. However, resveratrol treatment alleviated these changes caused by MCAO injury. Moreover, MCAO injury induced decreases in phospho-Akt and phospho-GSK-3β protein levels, whereas resveratrol attenuated these decreases. Phosphorylations of Akt and GSK-3β act as a critical role for the suppression of apoptotic cell death. Thus, our finding suggests that resveratrol attenuates neuronal cell death in MCAO-induced cerebral ischemia and Akt/GSK-3β signaling pathway contributes to the neuroprotective effect of resveratrol.

Baicalin attenuates lipopolysaccharide-induced neuroinflammation in cerebral cortex of mice via inhibiting nuclear factor kappa B (NF-κB) activation

Baicalin is a plant-derived flavonoid that has anti-inflammatory and anti-oxidative effects. We investigated an anti-inflammatory effect of baicalin against lipopolysaccharide (LPS)-induced damage in cerebral cortex. Adult mice were divided into control, LPS-treated, and LPS and baicalin co-treated animals. LPS (250 µg/kg/day) and baicalin (10 mg/kg/day) were intraperitoneally injected for 7 days. LPS treatment induced histopathological changes in cerebral cortex, whereas baicalin protected neuronal cells against LPS toxicity. Moreover, baicalin treatment attenuated LPS-induced increases of reactive oxygen species and oxidative stress in cerebral cortices. Ionized calcium binding adaptor molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP) are known as markers of activated microglia and astrocyte, respectively. Results of Western blot and immunofluorescence staining showed that LPS exposure induces increases of Iba-1 and GFAP expressions, whereas baicalin alleviates LPS-induced increases of these proteins. Baicalin also prevented LPS-induced increase of nuclear factor kappa B (NF-κB). LPS treatment led to increases of pro-inflammatory factors including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). Increases of these pro-inflammatory mediators were attenuated in baicalin co-treated animals. These results demonstrated that baicalin regulates neuroglia activation and modulates inflammatory factors in LPS-induced neuronal injury. Thus, our findings suggest that baicalin exerts a neuroinflammatory effect against LPS-induced toxicity through decreasing oxidative stress and inhibiting NF-κB mediated inflammatory factors, such as IL-1β and TNF-α.

Quercetin alleviates the injury-induced decrease of protein phosphatase 2A subunit B in cerebral ischemic animal model and glutamate-exposed HT22 cells

Quercetin is a plant flavonoid that has anti-oxidant, anti-inflammatory, anti-cancer, and anti-ischemic properties. Moreover, quercetin exerts neuroprotective effects against focal cerebral ischemia. Protein phosphatase 2A (PP2A) is a form of serine/threonine phosphatase that modulates various biological functions. Among PP2A subunit types, subunit B exists abundantly in brain tissue and plays an essential function in nervous system. We previously reported the decrease of PP2A subunit B in focal cerebral animal model. This study explored the change of PP2A subunit B expression by quercetin treatment in cerebral ischemic animal model and glutamate-treated hippocampal-derived (HT22) cell culture. Quercetin (10 mg/kg) or vehicle was injected intraperitoneally into male rats before 30 min of middle cerebral artery occlusion (MCAO), and cerebral cortices were isolated 24 hr after MCAO. MCAO induced the neurological behavioral deficit and increased infarct volume. However, quercetin treatment attenuated the increase of neurological deficit and infarction. We detected the alleviation of MCAO-induced the decrease in PP2A subunit B by quercetin treatment using a proteomic approach. Reverse-transcription PCR and Western blot analyses confirmed lower PP2A subunit B expression levels in MCAO group with vehicle. However, quercetin treatment attenuated MCAO-induced this reduction. We also observed the neuroprotective effect of quercetin and the change of PP2A subunit B expression in glutamate-exposed HT22 cells. Glutamate exposure dramatically reduced cell viability and PP2A subunit B expression, and quercetin treatment significantly improved these decreases. We clearly showed that quercetin performs a neuroprotective function and modulates down-regulation of PP2A subunit B against MCAO injury and glutamate toxicity. Thus, our finding suggests that the regulation of PP2A subunit B by quercetin contributes to neuroprotective function in ischemic brain injury.

Treatability of organic fractions derived from secondary effluent by reverse osmosis membrane

Dissolved organic matters (DOMs) from two batches of secondary effluent collected from a local water reclamation plant were fractionated using column chromatographic method with non-ionic resins XAD-8, AG MP-50 and IRA-96. Seven isolated fractions were obtained from the fractionation study and these fractions were quantified using DOC, UV(254) and SUVA values. The fractionation study revealed that the secondary effluent samples comprised about 47.3-60.6% of hydrophobic and 39.4-52.7% of hydrophilic solutes. The treatability of each isolated fraction was investigated by subjecting each fraction to reverse osmosis (RO) treatment individually. It was noted that RO process could achieve high DOC rejections for acid and neutral fractions (ranging from 80% to 98% removal) probably due to the negative charge of RO membrane. The results obtained also indicated that hydrophobicity of DOMs is significant in determining treatability of organic species by RO process. The performance of RO in terms of DOC rejection of un-fractionated secondary effluent was also investigated to assess possible effects of interactions among organic fractions on their treatability by RO process. It was noted that DOC rejection associated with the un-fractionated secondary effluent was generally higher (ranging from 2% to 45%) than the corresponding rejection obtained from each individual fraction isolated from the secondary effluent. This finding suggested there is a beneficial interaction among the fractions that in turn has contributed towards a better overall DOC rejection performance by RO treatment.

Insulin regulates protein kinase CbetaII expression through enhanced exon inclusion in L6 skeletal muscle cells. A novel mechanism of insulin- and insulin-like growth factor-i-induced 5' splice site selection

The protein kinase Cbeta (PKCbeta) gene encodes two isoforms, PKCbetaI and PKCbetaII, as a result of alternative splicing. The unique mechanism that underlies insulin-induced alternative splicing of PKCbeta pre-mRNA was examined in L6 myotubes. Mature PKCbetaII mRNA and protein rapidly increased >3-fold following acute insulin treatment, while PKCbetaI mRNA and protein levels remained unchanged. Mature PKCbetaII mRNA resulted from inclusion of the PKCbetaII-specific exon rather than from selection of an alternative polyadenylation site. Increased PKCbetaII expression was also not likely accounted for by transcriptional activation of the gene or increased stabilization of the PKCbetaII mRNA, and suggest that PKCbetaII expression is regulated primarily at the level of alternative splicing. Insulin effects on exon inclusion were observed as early as 15 min after insulin treatment; by 20 min, a new 5'-splice site variant of PKCbetaII was also observed. After 30 min, the longer 5'-splice site variant became the predominate species through activation of a downstream 5' splice site. Similar results were obtained using IGF-I. Although the role of this new PKCbetaII mRNA species is presently unknown, inclusion of either PKCbetaII-specific exon results in the same PKCbetaII protein.

15-Hydroxyeicosatetraenoic acid dehydrogenase activity in microsomal fraction of mouse liver homogenate

The microsomal fraction of mouse liver homogenate showed NAD(P)-dependent dehydrogenase activity involved in the conversion of 15-hydroxyeicosatetraenoic acid to 15-ketoeicosatetraenoic acid, which was determined quantitatively by HPLC assay. This enzyme, tightly bound to membranes and relatively stable, possessed apparent values of Km of 8.3 microM and Vmax of 2.8 nmoles/mg.min in the oxidation of 15-HETE, and gave an optimum pH of 9.8. Additionally, the enzyme, not susceptible to the inhibition by indomethacin and showing a similar cosubstrate specificity between NAD and NADP, utilized other hydroxylated eicosanoids as substrates, based on HPLC analyses.

Soybean lipoxygenase-catalyzed formation of lipoxin A and lipoxin B isomers from arachidonic acid via 5,15-dihydroperoxyeicosatetraenoic acid

Soybean lipoxygenase converted arachidonic acid to a group of polar products (lambda max, 300-301 nm), which were increasingly formed during the continued incubation at 20 degrees C after the initial incubation (2 hrs, at 4 degrees C). These products were identified as lipoxin A and B isomers, based on the chromatographic and spectrometric analyses. In further chromatographic analyses, the lipoxin A and B isomers were separated into at least three isomers, respectively. The exposure of 5,15-dihydroperoxyeicosatetraenoic acid to the soybean lipoxygenase produced the identical product profile of chromatography, substantiating the intermediacy of 5,15-dihydroperoxyeicosatetraenoic acid in the soybean lipoxygenase-catalyzed formation of lipoxins. Based on these results, it is proposed that the conversion of arachidonic acid into lipoxins by soybean lipoxygenase may bear a mechanistic resemblance to the formation of lipoxins in the human leukocytes.

Use of adenine nucleotide derivatives to assess the potential of exo-active-site-directed reagents as species- or isozyme-specific enzyme inactivators. 3. Synthesis of adenosine 5'-triphosphate derivatives with N6- or 8-substituents bearing iodoacetyl groups

Several series of N6- or 8-substituted derivatives of adenosine 5'-triphosphate (ATP) were synthesized. N6-(omega-Aminoalkyl) derivatives of adenosine 5'-monophosphate (AMP) were converted into their omega-N-carbobenzyloxy derivatives, and these were converted, via the 2',3'-O-carbonyl derivatives of their 5'-phosphorimidazolidates, into the corresponding ATP derivatives. Hydrogenolytic removal of the carbobenzyloxy groups, followed by iodoacetylation of the omega-amino groups with N-(iodoacetoxy)succinimide, gave N6-R-ATP, where R = (CH2)nNHCOCH2I (n = 2--8) or (CH2)nCON)CH3)(CH2)mN(CH3)CO(CH2)nNHCOCH2I (n = m = 3; n = 3, m = 4; n = 4, m = 3; n = m = 4). Condensation of N6-(omega-aminoalkyl) derivatives of AMP with N-hydroxysuccinimide esters of omega-[N-(carbobenzyloxy)amino] carboxylic acids gave N6-(CH2)nNHCO(CH2)mNH-Cbz derivatives of AMP which, upon conversion to the corresponding derivatives of ATP, followed by removal of the carbobenzyloxy group and iodoacetylation, as described above, gave N6-(CH2)nNHCO(CH2)mNHCOCH2I-ATP derivatives (n = 3, m = 5 or 6; n = 4, m = 5; n = 6, m = 1--6). The same sequence of reactions starting with N6-[omega-(methylamino)alkyl] derivatives of N6-CH3-AMP gave N6-CH3, N6-(CH2)nH(CH3)CO(CH2)mNHCOCH2I derivatives of ATP (n = 4, m = 3, 5 or 6; n = 6, m = 5 or 6). Reaction of alpha, omega-diaminoalkanes with 8-Br-ATP gave 8-NH(CH2)nNH2 derivatives of ATP, which upon iodoacetylation gave 8-NH(CH2)nNHCOCH2I derivatives of ATP (n = 2, 4, 6, or 8). Substrate and inhibitor properties indicated that the ATP derivatives are potential exco-ATP-site-directed inactivators of hexokinases, adenylate kinases, and pyruvate kinases.