1.Synthesis and biological evaluation of 68Ga-NOTA-CD44: a novel tracer targeting atherosclerotic plaques
Bo WANG ; Li LI ; Xue YU ; Chuxin ZHANG ; Min YAN ; Huiling LI ; Huibin RU ; Ping WU ; Ruonan WANG ; Zhifang WU ; Sijin LI
Chinese Journal of Nuclear Medicine and Molecular Imaging 2024;44(2):104-108
Objective:To construct 68Ga-1, 4, 7-trizacyclononane-1, 4, 7-triacetic acid (NOTA)-CD44 as a novel atherosclerosis tracer targeting hyaluronic acid (HA), and evaluate its biological property and molecular imaging features. Methods:Low molecular weight (LMW) recombinant human CD44 protein was selected, and the C-terminal of the protein was modified by sulfonation and coupled to the bifunctional ligand NOTA to synthesize a novel molecular probe 68Ga-NOTA-CD44 targeting HA. The biological properties of the probe, such as labeling rate and in vitro stability, were studied. Three atherosclerotic plaque model mice and three normal C57BL/6 mice were studied by 68Ga-NOTA-CD44 microPET/CT imaging and pathological examination. Results:68Ga-NOTA-CD44 tracer was synthesized and purified with the radiochemical purity above 99%, and the specific activity was up to 62.22 MBq/nmol. lts stability was good in PBS, and the radiochemical purity was over 90% after incubation for 3 h. After intravenous injection, the probe was metabolized mainly by the kidneys, and its metabolic level decreased successively in the liver, lungs and blood. MicroPET/CT imaging results of atherosclerotic model mice suggested that the uptake in the plaque of abdominal aorta was higher at 60 min after injection, with SUV max and target/background ratio (TBR) max of 1.14±0.02 and 4.95±0.93, and the probe had certain atherosclerotic plaque eroded targeting, which was consistent with the pathological result. Conclusions:As a novel probe, 68Ga-NOTA-CD44 is simple to prepare and has a high labeling rate. It has good physicochemical properties and in vivo biological properties, and can display atherosclerotic eroded plaques sensitively. 68Ga-NOTA-CD44 has a promising prospect to be a new molecular probe for early noninvasive recognition of atherosclerotic eroded plaques.
2.Construction and characterization of lpxC deletion strain based on CRISPR/Cas9 in Acinetobacter baumannii
Zong-ti SUN ; You-wen ZHANG ; Hai-bin LI ; Xiu-kun WANG ; Jie YU ; Jin-ru XIE ; Peng-bo PANG ; Xin-xin HU ; Tong-ying NIE ; Xi LU ; Jing PANG ; Lei HOU ; Xin-yi YANG ; Cong-ran LI ; Lang SUN ; Xue-fu YOU
Acta Pharmaceutica Sinica 2024;59(5):1286-1294
Lipopolysaccharides (LPS) are major outer membrane components of Gram-negative bacteria. Unlike most Gram-negative bacteria,
3.Evaluation of Extrathyroidal Extension of Papillary Thyroid Microcarcinoma With Three-Dimensional Tomographic Ultrasound Imaging.
Ru-Yu LIU ; Yu-Xin JIANG ; Rui-Na ZHAO ; Xing-Jian LAI ; Chuan-Ying-Zi LU ; Lu-Ying GAO ; Ying WANG ; Xue-Hua XI ; Bo ZHANG
Acta Academiae Medicinae Sinicae 2023;45(3):361-365
Objective To evaluate extrathyroidal extension (ETE) in papillary thyroid microcarcinoma (PTMC) with three-dimensional tomographic ultrasound imaging (3D-TUI). Methods A total of 97 thyroid nodules of 79 patients with PTMC treated in PUMC Hospital from February 2016 to January 2018 were included in this study.Two ultrasound experts performed independent blinded assessment of the relationship between thyroid nodules and thyroid capsule by two-dimensional ultrasound (2D-US) and 3D-TUI.The results of 2D-US and 3D-TUI in evaluating ETE were compared with intraoperative findings and postoperative histological and pathological results. Results Among the 97 nodules,54 (55.7%) nodules had ETE.The diagnostic sensitivity (68.5% vs.37.0%;χ2=10.737,P=0.002),accuracy (74.5% vs.56.7%;χ2=6.686,P=0.015),and area under the receiver operating characteristic curve[0.761 (95%CI=0.677-0.845) vs.0.592 (95%CI=0.504-0.680);Z=3.500,P<0.001] of 3D-TUI were higher than those of 2D-US.However,3D-TUI and 2D-US showed no significant difference in the specificity (84.1% vs.81.4%;χ2=0.081,P=0.776),negative predictive value (67.9% vs.50.7%;χ2=3.645,P=0.066),or positive predictive value (84.1% vs.71.4%;χ2=1.663,P=0.240). Conclusion Compared with 2D-US,3D-TUI demonstrates increased diagnostic efficiency for ETE of PTMC.
Humans
;
Thyroid Nodule
;
Thyroid Neoplasms/diagnosis*
;
Carcinoma, Papillary/pathology*
;
Ultrasonography/methods*
;
Retrospective Studies
4.Clinical Comparison of the Efficacy of Systemic Thrombolysis,Catheter-Directed Thrombolysis,and AngioJet Percutaneous Mechanical Thrombectomy in Acute Lower Extremity Deep Venous Thrombosis.
Jin-Wang LI ; Jun XUE ; Fei GUO ; Lei HAN ; Ru-Bo BAN ; Xue-Liang WU
Acta Academiae Medicinae Sinicae 2023;45(3):410-415
Objective To compare the clinical effects of three treatment methods including systemic thrombolysis(ST),catheter-directed thrombolysis(CDT),and AngioJet percutaneous mechanical thrombectomy(PMT)in acute lower extremity deep venous thrombosis(LEDVT). Methods The data of 82 patients diagnosed with LEDVT in the Department of Vascular and Gland Surgery of the First Affiliated Hospital of Hebei North University from January 2017 to December 2020 were collected.The patients were assigned into a ST group(n=50),a CDT group(n=16),and a PMT group(n=16)according to different treatment methods.The efficacy and safety were compared among the three groups. Results Compared with that before treatment,the circumferential diameter difference of both lower limbs on days 1,2,and 3 of treatment in the ST,CDT,and PMT groups reduced(all P<0.001).The PMT group showed smaller circumferential diameter difference of lower limbs on days 1,2,and 3 of treatment than the ST group(all P<0.001)and smaller circumferential diameter difference of the lower patellar margin on day 1 of treatment than the CDT group(P<0.001).The PMT group showed higher diminution rate for swelling of the affected limb at the upper and lower edges of the patella than the ST group(P<0.001)and higher diminution rate for swelling at the upper edge of the patella than the CDT group(P=0.026).The incidence of complications after treatment showed no significant differences among the three groups(all P>0.05).The median of hospital stay in the PMT group was shorter than that in the ST and CDT groups(P=0.002,P=0.001).The PMT group had higher thrombus clearance rate than the ST group(P=0.002)and no significant difference in the thrombus clearance rate from the CDT group(P=0.361).The vascular recanalization rates in the PMT(all P<0.001)and CDT(P<0.001,P=0.002,P=0.009)groups 3,6,and 12 months after treatment were higher than those in ST group,and there were no significant differences between PMT and CDT groups(P=0.341,P=0.210,P=0.341). Conclusions ST,CDT,and PMT demonstrated significant efficacy in the treatment of LEDVT,and PMT was superior to ST and CDT in terms of circumferential diameter difference of the lower limbs,diminution rate for swelling of the affected limb,thrombus clearance rate,length of hospital stay,and long-term vascular recanalization.There was no obvious difference in safety among the three therapies.
Humans
;
Thrombolytic Therapy/methods*
;
Fibrinolytic Agents/therapeutic use*
;
Treatment Outcome
;
Thrombectomy/methods*
;
Venous Thrombosis/drug therapy*
;
Lower Extremity/blood supply*
;
Catheters
;
Retrospective Studies
5.Antidepressant mechanism of Shenling Kaixin Granules based on BDNF/TrkB/CREB pathway.
Yan XU ; Dong-Guang LIU ; Ting-Bo NING ; Jian-Guo ZHU ; Ru YAO ; Xue MENG ; Jing-Chun YAO ; Wen-Xue ZHAO
China Journal of Chinese Materia Medica 2023;48(8):2184-2192
To investigate the antidepressant mechanism of Shenling Kaixin Granules(SLKX) in treating chronic unpredictable mild stress(CUMS) model rats. Ninety male SD rats were randomly divided into control group, model group, Shugan Jieyu Capsules(110 mg·kg~(-1)) group and SLKX low-(90 mg·kg~(-1)), medium-(180 mg·kg~(-1)), and high-dose(360 mg·kg~(-1)) groups. Depression rat model was replicated by CUMS method. After treatment, the behavioral changes of rats were evaluated by sugar preference, open field, elevated cross maze and forced swimming experiments. The contents of interleukin 1 beta(IL-1β), tumor necrosis factor α(TNF-α), brain-derived neurotrophic factor(BDNF) and 5-hydroxytryptamine(5-HT) in serum were determined by enzyme linked immunosorbent assay(ELISA), and the activities of superoxide dismutase(SOD) and catalase(CAT) in hippocampal CA1 region were also detected. Pathological changes in hippocampal CA1 region were detected by hematoxylin-eosin(HE) staining, and Western blot was used to determine the expression of nerve growth factor(NGF), BDNF, phospho-tyrosine kinase receptor(p-TrkB)/TrkB, phospho-cAMP-response element binding protein(p-CREB)/CREB, nuclear factor E2 related factor 2(Nrf2), heme oxygenase 1(HO-1), B-cell lymphoma-2(Bcl-2)/Bcl-2 associated X protein(Bax) and caspase-3 in hippocampal CA1 region. RESULTS:: showed that compared with the control group, the model group had decreased sugar preference, reduced number of entries and time spent in the center of open field and shortened total distance of movement, reduced number of entries and proportion of time spent in open arm, and increased number and time of immobility in forced swimming experiment. Additionally, the serum contents of IL-1β and TNF-α and the expression of caspase-3 were higher, while the contents of BDNF and 5-HT, the activities of SOD and CAT in hippocampal CA1 region, the expressions of NGF, BDNF, p-TrkB/TrkB, p-CREB/CREB, HO-1 and Bcl-2/Bax, and the Nrf2 nuclear translocation were lower in model group than in control group. Compared with the conditions in model group, the sugar preference, the number of entries and time spent in the center of open, total distance of movement, and the number of entries and proportion of time spent in open arm in treatment groups were increased while the number and time of immobility in forced swimming experiment were decreased; the serum contents of IL-1β and TNF-α and the expression of caspase-3 were down regulated, while the contents of BDNF and 5-HT, the activities of SOD and CAT in hippocampal CA1 region, the expressions of NGF, BDNF, p-TrkB/TrkB, p-CREB/CREB, HO-1, Bcl-2/Bax, and Nrf2 nuclear translocation were enhanced. In conclusion, SLKX might regulate the Nrf2 nucleus translocation by activating BDNF/TrkB/CREB pathway, lower oxidative stress damage in hippocampus, inhibit caspase-3 activity, and reduce apoptosis of hippocampal nerve cells, thereby playing an antidepressant role.
Rats
;
Male
;
Animals
;
bcl-2-Associated X Protein/metabolism*
;
Caspase 3/metabolism*
;
Nerve Growth Factor/metabolism*
;
Brain-Derived Neurotrophic Factor/metabolism*
;
Signal Transduction
;
Tumor Necrosis Factor-alpha/metabolism*
;
Serotonin/metabolism*
;
NF-E2-Related Factor 2/metabolism*
;
Rats, Sprague-Dawley
;
Antidepressive Agents/pharmacology*
;
Hippocampus/metabolism*
;
Superoxide Dismutase/metabolism*
;
Sugars/pharmacology*
;
Depression/genetics*
;
Stress, Psychological/metabolism*
6.Establishment of a screening cell model for cannabinoid type 1 receptor agonists
Xiao-tong WANG ; Cheng-lu ZHANG ; Ru-xue BO ; Shi-qi ZHOU ; Nai-hong CHEN ; Yu-he YUAN
Acta Pharmaceutica Sinica 2023;58(6):1603-1610
Cannabinoid receptors are one of the most expressed G protein-coupled receptors in the central nervous system, which are potential drug targets for inflammation, pain and drug abuse. Cannabinoid receptors are composed of type 1 receptor (CB1R), type 2 receptor (CB2R) and other receptors, of which CB1R plays a vital role in regulating central memory, cognition, and motor function. Therefore, screening CB1R agonists has potential value in treating nervous system diseases. In this study, the intracellular loop 3 (ICL3) domain of CB1R was replaced with a circular-permutated enhanced green fluorescent protein (cpEGFP). After infecting HEK 293T cells with lentivirus particles, we obtained a stable cell line that was overexpressed human CB1R-cpEGFP after puromycin selection. The interaction between receptor agonists and CB1R led to the change of receptor conformation, resulting in de-protonation of the EGFP, and enhancing the fluorescence intensity. Therefore, active CB1R compounds could be verified by measuring the fluorescence intensity. Using CB1R agonist arachidonyl-2′-chloroethylamide (ACEA) as a positive control to evaluate the reliability of this model, studies have shown that ACEA could induce receptor activation and increase fluorescence intensity, while antagonist rimonabant inhibited receptor activation with unchanged fluorescence intensity. In conclusion, this study successfully constructed a fluorescent probe screening model for CB1R agonists.
7.Incidence and prognosis of olfactory and gustatory dysfunctions related to infection of SARS-CoV-2 Omicron strain: a national multi-center survey of 35 566 population.
Meng Fan LIU ; Rui Xia MA ; Xian Bao CAO ; Hua ZHANG ; Shui Hong ZHOU ; Wei Hong JIANG ; Yan JIANG ; Jing Wu SUN ; Qin Tai YANG ; Xue Zhong LI ; Ya Nan SUN ; Li SHI ; Min WANG ; Xi Cheng SONG ; Fu Quan CHEN ; Xiao Shu ZHANG ; Hong Quan WEI ; Shao Qing YU ; Dong Dong ZHU ; Luo BA ; Zhi Wei CAO ; Xu Ping XIAO ; Xin WEI ; Zhi Hong LIN ; Feng Hong CHEN ; Chun Guang SHAN ; Guang Ke WANG ; Jing YE ; Shen Hong QU ; Chang Qing ZHAO ; Zhen Lin WANG ; Hua Bin LI ; Feng LIU ; Xiao Bo CUI ; Sheng Nan YE ; Zheng LIU ; Yu XU ; Xiao CAI ; Wei HANG ; Ru Xin ZHANG ; Yu Lin ZHAO ; Guo Dong YU ; Guang Gang SHI ; Mei Ping LU ; Yang SHEN ; Yu Tong ZHAO ; Jia Hong PEI ; Shao Bing XIE ; Long Gang YU ; Ye Hai LIU ; Shao wei GU ; Yu Cheng YANG ; Lei CHENG ; Jian Feng LIU
Chinese Journal of Otorhinolaryngology Head and Neck Surgery 2023;58(6):579-588
Objective: This cross-sectional investigation aimed to determine the incidence, clinical characteristics, prognosis, and related risk factors of olfactory and gustatory dysfunctions related to infection with the SARS-CoV-2 Omicron strain in mainland China. Methods: Data of patients with SARS-CoV-2 from December 28, 2022, to February 21, 2023, were collected through online and offline questionnaires from 45 tertiary hospitals and one center for disease control and prevention in mainland China. The questionnaire included demographic information, previous health history, smoking and alcohol drinking, SARS-CoV-2 vaccination, olfactory and gustatory function before and after infection, other symptoms after infection, as well as the duration and improvement of olfactory and gustatory dysfunction. The self-reported olfactory and gustatory functions of patients were evaluated using the Olfactory VAS scale and Gustatory VAS scale. Results: A total of 35 566 valid questionnaires were obtained, revealing a high incidence of olfactory and taste dysfunctions related to infection with the SARS-CoV-2 Omicron strain (67.75%). Females(χ2=367.013, P<0.001) and young people(χ2=120.210, P<0.001) were more likely to develop these dysfunctions. Gender(OR=1.564, 95%CI: 1.487-1.645), SARS-CoV-2 vaccination status (OR=1.334, 95%CI: 1.164-1.530), oral health status (OR=0.881, 95%CI: 0.839-0.926), smoking history (OR=1.152, 95%CI=1.080-1.229), and drinking history (OR=0.854, 95%CI: 0.785-0.928) were correlated with the occurrence of olfactory and taste dysfunctions related to SARS-CoV-2(above P<0.001). 44.62% (4 391/9 840) of the patients who had not recovered their sense of smell and taste also suffered from nasal congestion, runny nose, and 32.62% (3 210/9 840) suffered from dry mouth and sore throat. The improvement of olfactory and taste functions was correlated with the persistence of accompanying symptoms(χ2=10.873, P=0.001). The average score of olfactory and taste VAS scale was 8.41 and 8.51 respectively before SARS-CoV-2 infection, but decreased to3.69 and 4.29 respectively after SARS-CoV-2 infection, and recovered to 5.83and 6.55 respectively at the time of the survey. The median duration of olfactory and gustatory dysfunctions was 15 days and 12 days, respectively, with 0.5% (121/24 096) of patients experiencing these dysfunctions for more than 28 days. The overall self-reported improvement rate of smell and taste dysfunctions was 59.16% (14 256/24 096). Gender(OR=0.893, 95%CI: 0.839-0.951), SARS-CoV-2 vaccination status (OR=1.334, 95%CI: 1.164-1.530), history of head and facial trauma(OR=1.180, 95%CI: 1.036-1.344, P=0.013), nose (OR=1.104, 95%CI: 1.042-1.171, P=0.001) and oral (OR=1.162, 95%CI: 1.096-1.233) health status, smoking history(OR=0.765, 95%CI: 0.709-0.825), and the persistence of accompanying symptoms (OR=0.359, 95%CI: 0.332-0.388) were correlated with the recovery of olfactory and taste dysfunctions related to SARS-CoV-2 (above P<0.001 except for the indicated values). Conclusion: The incidence of olfactory and taste dysfunctions related to infection with the SARS-CoV-2 Omicron strain is high in mainland China, with females and young people more likely to develop these dysfunctions. Active and effective intervention measures may be required for cases that persist for a long time. The recovery of olfactory and taste functions is influenced by several factors, including gender, SARS-CoV-2 vaccination status, history of head and facial trauma, nasal and oral health status, smoking history, and persistence of accompanying symptoms.
Female
;
Humans
;
Adolescent
;
SARS-CoV-2
;
Smell
;
COVID-19/complications*
;
Cross-Sectional Studies
;
COVID-19 Vaccines
;
Incidence
;
Olfaction Disorders/etiology*
;
Taste Disorders/etiology*
;
Prognosis
8.Correlation between daily fluid intake behavioral habits and pathological characteristics of upper tract urothelial carcinoma.
Zhi Hua LI ; Chun Ru XU ; Ying LIU ; Hua GUAN ; Meng ZHANG ; Xin Yan CHE ; Qi TANG ; Yan Bo HUANG ; Xue Song LI ; Li Qun HOU
Journal of Peking University(Health Sciences) 2022;54(4):621-627
OBJECTIVE:
To investigate the correlation between drinking habits and pathological characteristics of patients with upper tract urothelial carcinoma (UTUC).
METHODS:
A preoperative questionnaire survey was conducted to understand the drinking habits of UTUC patients who were admitted to the Department of Urology, Peking University First Hospital for radical nephroureterectomy within one year from August 2020 to July 2021, and statistical analysis was performed in combination with their postoperative pathological characteristics. The statistical procedure was performed using SPSS 22.0 software, and firstly, the preliminary analysis was performed one by one using the columnar χ2 test on the pathological characteristics of UTUC tumors as the dependent variable and the factors related to patients' general information, past history and drinking habits as the independent variables, and the independent variables that met P < 0.2 between the case and control groups for each dependent variable were specified for screening. The screened variables were included in the binary Logistic regression analysis. A difference of P < 0.05 was used to indicate a statistically significant difference.
RESULTS:
A total of 239 patients, 134 males and 105 females, with a mean age of (68.1±9.98)years and a median disease duration of 4.8 months, were included in this study. Multifactorial Logistic regression results suggested that after adjusting for the effects of other variables, UTUC patients who had the habit of drinking at least once every hour during the daytime had a significantly increased risk of high grade (G3) tumors(OR=1.941, 95%CI: 0.352-1.029, P < 0.01); these patients also had a significantly decreased risk of multifocal UTUC tumors (OR=0.344, 95% CI: 1.18-5.582, P=0.004). The patients who had the habit of drinking over 100 mL water each time had a significantly decreased risk of mutifocal UTUC incidence (OR=0.477, 95%CI: 0.225-1.012, P=0.046). Patients who pay attention to daily water intakes had a significantly increased risk of renipelvic carcinoma (OR=2.530, 95%CI: 1.434-4.463, P=0.001) and a significantly decreased risk of ureteral carcinoma (OR=0.314, 95%CI: 0.172-0.573, P < 0.01). Other variables included in the regression model did not differ significantly in their effects on the occurrence of tumor pathological characteristics.
CONCLUSION
Having the awareness of drinking water every 1 h during the day, drinking over 100 mL water each time, having the awareness of daily drinking habits correlated significantly with pathological characteristics of UTUC such as the presence of G3 tumor, multifocal tumors and location of the tumor. This conclusion still needs to be verified by subsequent trials with higher levels of evidence.
Carcinoma, Transitional Cell/surgery*
;
Female
;
Habits
;
Humans
;
Male
;
Neoplasm Recurrence, Local/epidemiology*
;
Retrospective Studies
;
Ureteral Neoplasms/surgery*
;
Urinary Bladder Neoplasms/surgery*
;
Water
9.Application of lymphocytes test in peripheral blood of patients with systemic sclerosis during the treatment.
Xiang Bo MA ; Xue Wu ZHANG ; Ru Lin JIA ; Ying GAO ; Hong Jiang LIU ; Yu Fang LIU ; Ying Ni LI
Journal of Peking University(Health Sciences) 2021;53(4):721-727
OBJECTIVE:
To explore the significance of lymphocytes in systemic sclerosis (SSc), by detecting the levels of T lymphocytes, B lymphocytes and natural killer (NK) cells, and analyzing the correlation between the lymphocytes and clinical laboratory indexes.
METHODS:
The numbers and proportion of T, CD4+T, CD8+T, B, and NK cells were detected by flow cytometry in peripheral blood of 32 SSc patients who had taken immunosuppressive drugs and 30 healthy controls (HC). The comparison of the lymphocyte subsets in SSc with them in the HC groups, and the correlation between the lymphocytes and other clinical and laboratory indicators were analyzed by the relevant statistical analysis.
RESULTS:
Compared with the HC group, the numbers of T, CD4+T, CD8+T, and NK cells in peripheral blood of SSc group, who had taken immunosuppressive drugs, were significantly decreased (P < 0.05). More-over, the proportion of NK cells in peripheral blood of the SSc group was also significantly lower than that in the HC group (P=0.004). In addition, all the lymphocyte subsets were decreased in peripheral blood of more than 65% of the SSc patients who had taken immunosuppressive drugs. Compared with CD4+T normal group, the positivity of Raynaud's phenomenon, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) was significantly increased in CD4+T reduction group, respectively (P=0.024, P < 0.001, P=0.018). ESR was higher in CD8+T reduction group than CD8+T normal group (P=0.022). The prevalence of fingertip ulcer was significantly increased in B cell decrease group (P=0.019). Compared with NK cell normal group, the prevalence of fingertip ulcer was significantly increased in NK cell lower group (P=0.033), IgM was remarkablely decreased yet (P=0.049). The correlation analysis showed that ESR was negatively correlated with the counts of T lymphocytes (r=-0.455, P=0.009), CD4+T lymphocytes (r=-0.416, P=0.018), CD8+T lymphocytes (r=-0.430, P=0.014), B cells (r=-0.366, P=0.039).
CONCLUSION
The number of CD4+T, CD8+T, B, and NK cells significantly decreased in peripheral blood of SSc patients who had used immunosuppressive drugs, some lymphocyte subsets might be related with Raynaud's phenomenon and fingertip ulcer, and reflected the disease activity by negatively correlated with ESR and CRP; the numbers of lymphocyte subsets in peripheral blood should be detected regularly in SSc patients who had taken immunosuppressive drugs.
B-Lymphocytes
;
Flow Cytometry
;
Humans
;
Killer Cells, Natural
;
Lymphocyte Subsets
;
Scleroderma, Systemic
;
T-Lymphocyte Subsets
;
T-Lymphocytes
10.Engineering CrtW and CrtZ for improving biosynthesis of astaxanthin in Escherichia coli.
Di LI ; Yang LI ; Jiao-Yang XU ; Qing-Yan LI ; Jin-Lei TANG ; Shi-Ru JIA ; Chang-Hao BI ; Zhu-Bo DAI ; Xin-Na ZHU ; Xue-Li ZHANG
Chinese Journal of Natural Medicines (English Ed.) 2020;18(9):666-676
This study engineered β-carotene ketolase CrtW and β-carotene hydroxylase CrtZ to improve biosynthesis of astaxanthin in Escherichia coli. Firstly, crtW was randomly mutated to increase CrtW activities on conversion from β-carotene to astaxanthin. A crtW* mutant with A6T, T105A and L239M mutations has improved 5.35-fold astaxanthin production compared with the wild-type control. Secondly, the expression levels of crtW* and crtZ on chromosomal were balanced by simultaneous modulation RBS regions of their genes using RBS library. The strain RBS54 selected from RBS library, directed the pathway exclusively towards the desired product astaxanthin as predominant carotenoid (99%). Lastly, the number of chromosomal copies of the balanced crtW-crtZ cassette from RBS54 was increased using a Cre-loxP based technique, and a strain with 30 copies of the crtW*-crtZ cassette was selected. This final strain DL-A008 had a 9.8-fold increase of astaxanthin production compared with the wild-type control. Fed-batch fermentation showed that DL-A008 produced astaxanthin as predominant carotenoid (99%) with a specific titer of 0.88 g·L without addition of inducer. In conclusion, through constructing crtW mutation, balancing the expression levels between crtW* and crtZ, and increasing the copy number of the balanced crtW*-crtZ cassette, the activities of β-carotene ketolase and β-carotene hydroxylase were improved for conversion of β-carotene to astaxanthin with higher efficiency. The series of conventional and novel metabolic engineering strategies were designed and applied to construct the astaxanthin hetero-producer strain of E. coli, possibly offering a general approach for the construction of stable hetero-producer strains for other natural products.

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