Plasminogen improves lung lesions and hypoxemia in patients with COVID-19

BACKGROUND

Lungs from patients with coronavirus disease 2019 (COVID-19) have shown typical signs of acute respiratory distress syndrome (ARDS), formation of hyaline membrane mainly composed of fibrin and 'ground-glass' opacity. Previously, we showed plasminogen itself is a key regulator in fibrin degradation, wound healing and infection.

AIM

We aimed to investigate whether plasminogen can improve lung lesions and hypoxemia of COVID-19.

DESIGN

Thirteen clinically moderate, severe or critical COVID-19 patients were treated with atomization inhalation of freeze-dried plasminogen.

METHODS

Levels of their lung lesions, oxygen saturation and heart rates were compared before and after treatment by computed tomography scanning images and patient monitor.

RESULTS

After plasminogen inhalation, conditions of lung lesions in five clinically moderate patients have quickly improved, shown as the decreased range and density of 'ground glass' opacity. Improvements of oxygen saturation were observed in six clinically severe patients. In the two patients with critical conditions, the oxygen levels have significantly increased from 79-82% to 91% just about 1 h after the first inhalation. In 8 of 13 patients, the heart rates had slowed down. For the five clinically moderate patients, the difference is even statistically significant. Furthermore, a general relief of chest tightness was observed.

CONCLUSION

Whereas it is reported that plasminogen is dramatically increased in adults with ARDS, this study suggests that additional plasminogen may be effective and efficient in treating lung lesions and hypoxemia during COVID-19 infections. Although further studies are needed, this study highlights a possible hope of efficiently combating this rapid epidemic emergency.

FRI0443 CLINICAL CHARACTERISTICS AND RELATED FACTORS OF COMMON RHEUMATIC DISEASES COMPLICATED WITH TUBERCULOSIS INFECTION

Background:

Rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and syndrome(SS) are common rheumatic diseases with high incidence. Patients with those rheumatic diseases are at high risk of tuberculosis (TB) infection. However, manifestations can be atypical and easily confused with those of rheumatic disease itself. For those patients, diagnosis is usually much more difficult and further make treatment delayed. Sometimes it may lead to mistreatment. Therefore, it is important to recognize the clinical characteristics of those patients.

Objectives:

To explore the clinical characteristics and high risk factors of common systemic rheumatism complicated with tuberculosis infection.

Methods:

A total of 3,906 cases of RA, SLE, and SS common systemic rheumatism diagnosed in the People’s Hospital of Sichuan Province from January 2007 to January 2017 were collected with carefully exclusion with other infectious diseases and neoplastic disease. One hundred and five patients with TB were included as infection group, including 42 cases of RA, 41 cases of SLE, and 22 cases of SS. In the control group, 84 patients with RA, 82 patients with SLE, and 44 patients with SS were randomly selected from the corresponding rheumatoid non-infected patients hospitalized during the same period.

Results:

Fever was the most common symptom among 42 cases of RA, 41 cases of SLE, and 22 cases of SS with TB, accounting for 83.3%, 92.7%, and 68.2%, respectively. Cough, weight loss or fatigue was less common. For 41 cases of SLE and 22 cases of SS with TB, the proportion of pulmonary was 46.3%, 59.01%, respectively.In TB infection group, 27 cases of RA, 21 cases of SLE, and 13 cases of SS with TB had two or more chest CT findings, accounting for 59%, 57%, 62%, respectively. Lesions located in the posterior or posterior segment which TB usually affected were 9 cases(33.3%),9cases(42.9%),6cases(27.2%),respectively.The daily average dose of hormones within 1 year in TB infection group was higher than that in the control group (P<0.05). For SLE patients, lower counts of CD4+TL were found in TB infection group (P<0.05), while no such differences were found in RA and SS group.

Conclusion:

Patients with RA who have TB infection are mainly pulmonary TB. For SLE and SS patients, the chance of pulmonary tuberculosis and extra-pulmonary tuberculosis is similar.Symptoms of RA, SLE, SS with TB, such as fever, cough, weight loss, fatigue, are similar with the primary disease or other infection. Chest imaging is diversity. It is difficult to diagnose.Daily average dose of hormone within one year may be a common risk factor for RA, SLE and SS patients with TB. Decreased CD4+TL may also be a risk factor for SLE patients with TB.

References:

[1]Cantini F, Nannini C, Niccoli L, et al. Risk of Tuberculosis Reactivation in Patients with Rheumatoid Arthritis, Ankylosing Spondylitis, and Psoriatic Arthritis Receiving Non-Anti-TNF-Targeted Biologics[J]. Mediators of Inflammation, 2017, 2017(6):1-15.

[2]Ruangnapa K, Dissaneewate P, Vachvanichsanong P. Tuberculosis in SLE patients: rare diagnosis, risky treatment.[J]. Clinical & Experimental Medicine, 2015, 15(3):429-432.

[3]Manuela D F, Bruno L, Martina S, et al. Lung Infections in Systemic Rheumatic Disease: Focus on Opportunistic Infections[J]. International Journal of Molecular Sciences, 2017, 18(2):293-315.

[4]Disseminated tuberculosis masquerading as a presentation of systemic lupus erythematosus.Li JC, Fong W, Wijaya L, Leung YY.Int J Rheum Dis. 2017 Oct 2. doi: 10.1111/1756-185X.13195.

[5]Handa R, Upadhyaya S, Kapoor S, et al. Tuberculosis and biologics in rheumatology: India – A special situation[J]. International Journal of Rheumatic Diseases, 2017, 51(2):115.

Disclosure of Interests:

None declared

SAT0209 PREVALENCE AND RELATED FACTORS OF SLEEP DISTURBANCE IN PATIENTS WITH PRIMARY SJÖGREN’S SYNDROME

Background:

The incidence of primary Sjögren’s syndrome(pSS) is increasing gradually,and it was ranking second among connective tissue diseases(CTDs)in China.Studies recently have shown that many patients with various CTDs have sleep disturbances,which seriously degraded the patient’s quality of life.As well known, Sleep is an important physiological process to maintain human metabolism, tissue repair,and homeostasis. At present,there are relatively several studies on sleep quality in patients with Rheumatoid arthritis(RA)and Systemic lupus erythematosus(SLE),but less reports on pSS in China have been published.Therefore,it is important to explore the quality of sleep and its influencing factors in such patients.

Objectives:

The purpose of this study is to evaluate the quality of sleep and related factors in China Mainland patients with primary Sjögren’s syndrome(pSS),and to provide reference and theoretical basis for constructing targeted sleep interventions and improve their quality of life.

Methods:

A all of 103 pSS patients and 40 matched healthy controls were enrolled in a comparative study of sleep quality using the Pittsburgh Sleep Quality Index(PSQI),and demographic,clinical,and laboratory data were collected from them.The patients completed questionnaires on the European League Against Rheumatism (EULAR)SS Patient Reported Index(ESSPRI), EULAR SS Disease Activity Index (ESSDAI),Xerostomia inventory(XI)with the help of researchers,Pain and fatigue were evaluated with a 100-mm visual analogue scale(VAS).Generalized Anxiety Disorder(GAD-7) and Patient Health Questionnaire(PHQ-9) were used to assess anxiety and depression separately,and whether they have autonomic symptoms (such as sweating, palpitations.)will be asked.

Results:

The PSQI score and the frequency of poor sleep quality(PSQI>7) were higher in the pSS patients (11.60±5.03,71.8%)than the healthy controls(5.98±3.85,25%).Poor sleepers had a significantly higher GAD-7,PHQ-9,XI,ESSPRI,pain and fatigue VAS,and longer disease duration than good sleepers.Additionally, poor sleepers show more frequent autonomic symptoms.Sleep quality of patients with pSS was positive correlated with GAD-7,PHQ-9,XI,ESSPRI,pain and fatigueVAS scores,but no correlation with disease activity.Meanwhile,depression is a independent factor of sleep quality.

Conclusion:

Our study showed that the sleep disturbance seen in patients with pSS may contribute to the depression associated with this disease,Future research should investigate that whether antidepressant treatment improve sleep and directly improve quality of life.

References:

[1]AustadC, Kvien TK, Olsen I C.Sleep disturbance in patients with rheumatoid arthritis is related to fatigue, disease activity,and other patient-reported outcomes[J]. Scandinavian journal of rheumatology, 2017, 46(2): 95-103.

[2]Lewis I, Hackett K L,Ng W F,et al.A two-phase cohort study of the sleep phenotype within primary Sjögren’s syndrome and its clinical correlates[J].Clinical and experimental rheumatology,2019,37(3):78-82.

[3]Chung S W, Hur J, Ha Y J, et al. Impact of sleep quality on clinical features of primary Sjögren’s syndrome[J]. The Korean journal of internal medicine, 2019,34(5):1154.

[4]Liu X, Tang M, Hu L. Reliability and validity of the Pittsburgh sleep quality index[J].Chinese journal of psychiatry,1996,29:103-107.

[5]Grabovac I,Haider S, Berner C,et al.Sleep quality in patients with rheumatoid arthritis and associations with pain, disability, disease duration, and activity[J].Journal of clinical medicine,2018,7(10):336.

Disclosure of Interests:

None declared

Sustained IFN-I stimulation impairs MAIT cell responses to bacteria by inducing IL-10 during chronic HIV-1 infection

Mucosal-associated invariant T (MAIT) cells in HIV-1-infected individuals are functionally impaired by poorly understood mechanisms. Single-cell transcriptional and surface protein analyses revealed that peripheral MAIT cells from HIV-1-infected subjects were highly activated with the up-regulation of interferon (IFN)-stimulated genes as compared to healthy individuals. Sustained IFN-α treatment suppressed MAIT cell responses to Escherichia coli by triggering high-level interleukin-10 (IL-10) production by monocytes, which subsequently inhibited the secretion of IL-12, a crucial costimulatory cytokine for MAIT cell activation. Blocking IFN-α or IL-10 receptors prevented MAIT cell dysfunction induced by HIV-1 exposure in vitro. Moreover, blocking the IL-10 receptor significantly improved anti-Mycobacterium tuberculosis responses of MAIT cells from HIV-1-infected patients. Our findings demonstrate the central role of the IFN-I/IL-10 axis in MAIT cell dysfunction during HIV-1 infection, which has implications for the development of anti-IFN-I/IL-10 strategies against bacterial coinfections in HIV-1-infected patients.

Correction to: Pelvic fat volume reduction with preoperative very low energy diet (VLED): implications for rectal cancer surgery in the obese

Due to substantial contributions by Dr. Phillip Malouf and Dr. Stephen Bell.

Pelvic fat volume reduction with preoperative very low energy diet (VLED): implications for rectal cancer surgery in the obese

BACKGROUND

Obese patients have higher complication rates after pelvic surgery. Laparoscopic rectal surgery may not be possible in the obese individual due to mesorectal, total pelvic and general visceral fat volumes. Very low energy diets reduce visceral fat but the changes within the pelvis and mesorectum are unknown. The aim of the present study was to quantify the proportion of fat lost from total pelvic and mesorectal fat with a very low energy diet (VLED) and define simple, accessible measurements that correlate with expected volume reduction.

METHODS

A study was conducted on proportion change in mesorectal and intrapelvic fat volumes in patients on a VLED prior to bariatric surgery at the Alfred Hospital in Melbourne. The VLED was a standardized 4-week meal replacement. Proportion change in mesorectal and intrapelvic fat volumes were measured. Patients had standardized pre-diet and post-diet magnetic resonance imaging (MRI) of the pelvis. Body mass index, weight and girth measures were obtained. Adipose quantification analysis was performed using Q-Fat.

RESULTS

Nine patients were included in this study, who were preparing for bariatric (not colorectal) surgery (5 females, median age 42 years, range 27-59 years) pre-protocol body mass index was 55.8 (range 39.5-60.6 kg/m²); median weight was 163 kg. Median mesorectal fat reduction was 29.9% (range 11.6-66.6%). Linear regression showed a relationship between the amount of mesorectal fat reduction and two variables: patient height and the distance from S1 to the posterior aspect of the rectum on MRI. The relationship predicted response to the diet (R² 67%, p = 0.040).

CONCLUSIONS

Very low energy diets result in a clinically significant reduction in mesorectal fat with a lesser change in total pelvic fat, suggesting that very low energy diets may be useful for preparation for pelvic surgery in the obese. The distance from S1 to the posterior rectum correlates well with mesorectal reduction, making this a valuable clinical tool when volumetric analysis is not possible. This analysis is limited to the quantification of the effect of the diet and cannot comment on the safety of this approach before pelvic cancer surgery.

[Effects of parthenolide on estradiol-synthesizing enzyme, ER isoforms and VEGF in human endometriotic stromal cells]

Objective: To evaluate the effects of parthenolide on estradiol-synthesizing enzyme, steroidogenic acute regulatory protein (StAR), and ER isoforms,VEGF in human endometriotic stromal cells. Methods: Primary endometriotic stromal cells were treated with different concentrations (1, 5, 10 and 20 μmol/L) of parthenolide. The mRNA of StAR, ER isoforms (ERα and ERβ), PR, vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), tumour necrosis factor-α (TNFα), tumour necrosis factor receptor (TNFR) 1, TNFR2 were measured by real-time PCR. The levels of estradiol and progesterone in the cell supernatant were measured by ELISA. Results: Different concentrations of parthenolide could up-regulate the mRNA of StAR in primary endometriotic stromal cells (F=5.722, P<0.05); the mRNA of StAR in the group of 20 μmol/L was significantly higher than that of the control group [2.6±0.3 versus 1.0, P<0.01]. Different concentrations of parthenolide could down-regulate the mRNA of ERα (F=6.921, P<0.01); the mRNA of ERα in the group of 20 μmol/L and 10 μmol/L were significantly lower than those of the control group [0.2±0.3 versus 0.3±0.3 versus 1.0, all P<0.05]. Different concentrations of parthenolide could down-regulate the ratios of ERα/ERβ mRNA levels (F=4.209, P<0.05). Different concentrations of parthenolide could up-regulate the mRNA of VEGF and TNFR1 (F=10.964, P<0.01; F=7.286, P<0.01). There were no statiscal significances with different concentrations of parthenolide on the mRNA of ERβ, PR, IL-6, TNFα and TNFR2, and the levels of estradiol and progesterone in the cell supernatant (all P>0.05). Conclusions: Parthenolide may regulate the expression of estradiol-synthesizing enzyme, ER isoforms and angiogenesis in endometriotic stromal cells. Parthenolide may promote the development of endometriosis.

Endoscopic submucosal multi-tunnel dissection for large early esophageal cancer lesions

OBJECTIVE

To evaluate the safety and efficacy of endoscopic submucosal multi-tunnel dissection (ESMTD) for early esophageal cancer lesions larger than 3 cm in diameter or cumulatively greater than 1/2 lumen size.

METHOD

Early esophageal cancer lesions in 15 patients were detected by endoscopy and endoscopic ultrasonography in our endoscopy center from December 2012 to June 2015. All lesions were successfully resected by ESMTD and diagnosed by pathology, and therapeutic efficiency and safety were followed after surgery.

RESULTS

All 15 of the early esophageal cancer lesions were resected by ESMTD. The pathological results showed 9 moderately differentiated and 6 highly differentiated squamous cell carcinomas. En bloc resection was achieved in 13 lesions, with negative lateral and basal margins on pathology, whereas the other 2 required additional surgery. The average diameter of the resected lesions was 4.2±0.9 cm. The mean procedure time was 94.7±52.9 min. Esophageal stenosis was observed in 7 patients for whom esophageal water balloon dilatation was performed. No residual or recurrent lesion was found during the 6-36-month follow-up period.

CONCLUSION

ESMTD is a safe and efficient technique for treating large early esophageal cancer lesions. Grasping the key techniques of this procedure can reduce operating difficulty and shorten the operating time.

[Prediction of syncope with nonlinear dynamic analysis during head-up tilt in vasovagal syncope patients]

OBJECTIVE

To quantify the relationship between cerebral blood flow velocity and peripheral blood pressure during hypotension period, aiming to predict the brain hypotension before symptomatic occurrence.

METHODS

Twenty vasovagal syncope (VVS) patients who had a previous clinical history were selected in groups and 20 pair-matched control subjects underwent 70° tilt-up test. The subjects remained supine for 30 minutes before recordings when Doppler probes, electrodes and Finapres device were prepared. After continuous baseline recordings for 10 min, the subjects underwent head up tilt (HUT) test (70°), and were standing upright for 30 minutes or until syncope was imminent. For ethical reasons, the subjects were turned back to supine position immediately after SBP dropped to ≥20 mmHg, when their consciousness persisted. The point of syncope was synchronized for all the subjects by the point SBP reached the minima. Their beat-to-beat blood pressures (BP) were recorded continuously and bilateral middle cerebral artery (MCA) flow velocities were obtained with two 2 MHz Doppler probes from a transcranial Doppler ultrasonography (TCD) system. A nonlinear dynamic method--multimodal pressure flow (MMPF) analysis was introduced to access cerebral autoregulation during different time intervals. We introduced a new indicator--syncope index (SI), which was extracted from blood flow velocity (BFV) signal to evaluate the variation of cerebral vascular tension, and could reflect the deepness of dicrotic notch in BFV signal.

RESULTS

Compared with the syncope index of the baseline value at the beginning of the tilt test, SI in VVS group showed significantly lower when the VVS occurred (0.16±0.10 vs.0.27±0.10,P<0.01),while there was no significant difference in syncope index between the control group at the end of the tilt test and the baseline value at the beginning of the tilt test. For those VVS patients, pulse index and resistance index had no significant change. Syncope index decreased significantly 3 minutes before the point of syncope (0.23±0.07 vs.0.29±0.07,P<0.01).

CONCLUSION

Dynamic regulation is exhausted when vasovagal syncope occurred. Tension decrease of small vessels could have some relationship with loss of the cerebral autoregulation capability. The proposed syncope index could be a useful parameter in predicting syncope of VVS patients since it decreased significantly up to 3 minutes earlier from the point of syncope.

Vibrational spectroscopic study on feed molecular structure properties of oil-seeds and co-products from Canadian and Chinese bio-processing and relationship with protein and carbohydrate degradation fractions in ruminant systems

The objective of this study was to apply ATR-FTIR spectroscopy to reveal feed molecular structure properties of oil-seeds and co-products and relationship with protein and carbohydrate degradation fractions in ruminant systems. The oil-seeds and co-products were from both various bio-processing industries in Canada and China. The protein and carbohydrate degradation fractions were evaluated with updated CNCPS system. Results showed that in the co-products from canola processing industries there are strong relationship between 1) soluble true protein (PA2) fraction and the following protein molecular structure spectral characteristics; spectral peak area of amide I and amide II (r = 0.56, P = 0.001), area of amide I (r = 0.67, P < 0.001), height of amide I (r = 0.74, P < 0.001), amide I and II ratio (r = 0.57, P = 0.001), α-helix (r = 0.82, P < 0.001), and β-sheet (r = 0.61, P < 0.001), 2) slowly degradable true protein (PB2) fraction and height of amide I (r = -0.60, P = 0.001), α-helix (r = -0.72, P < 0.001), and β-sheet (r = -0.51, P = 0.004), 3) soluble fiber (CB2) fraction and α-helix and β-sheet height ratio (r = -0.63, P < 0.001), and 4) unavailable NDF (CC) fraction and height of amide I (r = 0.55, P = 0.002). These results indicated feed molecular structure spectral properties of the oil-seeds and co-products related to CNCPS protein and carbohydrate degradation fractions in ruminant systems.

[Comparison of parameters for diffusion-weighted intravoxel incoherent motion imaging in lung cancer patients with different histopathological subtypes]

Objective: To explore the intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) model in lung cancer patients with different histopathological subtypes. Methods: A total of 105 patients were recruited, including 68 cases of adenocarcinoma, 22 cases of squamous carcinoma and 15 cases of small cell carcinoma. All patients underwent magnetic resonance examination consisting of axial IVIM-DWI sequence on a 3.0 T whole body scanner, then the standard ADC (sADC), diffusion coefficient (D), pseudo-diffusion coefficient(D(*)), perfusion fraction (f), distributed diffusion coefficient (DDC) and water diffusion heterogeneity index (α) were calculated for each lesion within the IVIM-DWI model. Results: Mean sADC values were (1.45±0.26) ×10(-3)mm(2)/s, (1.36±0.48) ×10(-3)mm(2)/s and (1.35±0.40) ×10(-3)mm(2)/s for adenocarcinoma, squamous carcinoma and small cell carcinoma, respectively. Mean f values were (59.75±16.37) %, (47.41±18.69) % and (48.96±19.88) % for adenocarcinoma, squamous carcinoma and small cell carcinoma, respectively. Mean α values were 0.72±0.13 for adenocarcinoma, 0.62±0.12 for squamous carcinoma, and 0.63±0.11 for small cell carcinoma, respectively. Statistical analyses indicated that the sADC, f and α values among different histopathological subtypes were significantly different (P<0.05), while there was no significant difference in D, D(*) and DDC values (P>0.05). Furthermore, the comparison showed that the sADC, f and α values of patients with adenocarcinoma were significantly higher than those with squamous carcinoma or small cell carcinoma (P<0.05), whereas there was no significant difference between squamous carcinoma group and small cell carcinoma group (P>0.05). Conclusions: The sADC, f and α values derived from the IVIM-DWI model can be used for comprehensive non-invasive evaluation of diffusion, perfusion and heterogeneity of microenvironment in lung cancer patients. And the IVIM-DWI model may be a promising tool for predicting histopathological subtypes of lung cancer.

Development of broad-band high-reflectivity multilayer film for positron emission tomography system

The use of non-ideal reflective materials and low-precision manual manufacturing technologies is a fundamental technical obstacle blocking the positron emission tomography (PET) systems from achieving better performances. We propose to address that long-standing obstacle with advanced multilayer dielectric coating technologies. We designed an broad-band multilayer high-reflectivity (HR) film that can be coated directly on the surface of ultra-precision polished lutetiumyttrium oxyorthosilicate (LYSO) scintillators. The film consists of 48 layers of TiO2/SiO2/HfO2 which are deposited on LYSO scintillator crystal alternately using the electron beam evaporation method. The overall thickness of the HR film is about 3μm. The HR film combines 3 quarter wavelength reflective films, with the central wavelengths of 365 nm, 430 nm and 570 nm respectively, to match the emission spectrum of the LYSO scintillator. The optical experimental results show that the HR film achieved an excellent average reflectivity of 99.50% at 8° incident angle for incident lights with wavelengths between 360 to 620 nm. The average reflectivity at 60° incident angle is higher than 90%. The results of the hardness experiments and the adhesive strength experiments show that the HR film has an excellent mechanical strength. The HR coating technology developed in this study is very attractive because it allows to "print" high-performance reflectors on a scintillator directly with high-precision, instead of manually gluing reflective films on the scintillator. Thus, we conclude that the HR film provides a viable solution to the long standing technical bottleneck that limits the development of high-performance detectors for advanced PET imaging.

Galectin-1 is required for the regulatory function of B cells

Galectin-1 (Gal-1) is required for the development of B cells in the bone marrow (BM), however very little is known about the contribution of Gal-1 to the development of B cell regulatory function. Here, we report an important role for Gal-1 in the induction of B cells regulatory function. Mice deficient of Gal-1 (Gal-1^−/−) showed significant loss of Transitional-2 (T2) B cells, previously reported to include IL-10⁺ regulatory B cells. Gal-1^−/− B cells stimulated in vitro via CD40 molecules have impaired IL-10 and Tim-1 expression, the latter reported to be required for IL-10 production in regulatory B cells, and increased TNF-α expression compared to wild type (WT) B cells. Unlike their WT counterparts, T2 and T1 Gal-1^−/− B cells did not suppress TNF-α expression by CD4⁺ T cells activated in vitro with allogenic DCs (allo-DCs), nor were they suppressive in vivo, being unable to delay MHC-class I mismatched skin allograft rejection following adoptive transfer. Moreover, T cells stimulated with allo-DCs show an increase in their survival when co-cultured with Gal-1^−/− T2 and MZ B cells compared to WT T2 and MZ B cells. Collectively, these data suggest that Gal-1 contributes to the induction of B cells regulatory function.

A first-principles study of the structural, mechanical and electronic properties of precipitates of Al2Cu in Al-Cu alloys

The properties of precipitates are important in understanding the strengthening mechanism via precipitation during heat treatment and the aging process in Al-Cu based alloys, where the formation of precipitates is sensitive to temperature and pressure. Here we report a first-principles investigation of the effect of temperature and pressure on the structural stability, elastic constants and formation free energy for precipitates of Al₂Cu, as well as their mechanical properties. Based on the formation enthalpy of Guinier-Preston (GP(I)) zones, the size of the GP(I) zone is predicted to be about 1.4 nm in diameter, which is in good agreement with experimental observations. The formation enthalpies of the precipitates are all negative, suggesting that they are all thermodynamically stable. The present calculations reveal that entropy plays an important role in stabilizing θ-Al₂Cu compared with θ_C'-Al₂Cu. The formation free energies of θ''-Al₃Cu, θ_C'-Al₂Cu, θ_D'-Al₅Cu₃ and θ_t'-Al₁₁Cu₇ increase with temperature, while those of θ'-Al₂Cu, θ_O'-Al₂Cu and θ-Al₂Cu decrease. The same trend is observed with the effect of pressure. The calculated elastic constants for the considered precipitation phases indicate that they are all mechanically stable and anisotropic, except θ_C'-Al₂Cu. θ_D'-Al₅Cu₃ has the highest Vicker's hardness. The electronic structures are also calculated to gain insight into the bonding characteristics. The present results can help in understanding the formation of precipitates by different treatment processes.