Unveiling the role of preceding seasonal influenza in the development of bacteremic pneumococcal pneumonia in older adults before the COVID-19 pandemic in Japan.

OBJECTIVE: We aimed to investigate the impact of preceding seasonal influenza on the clinical characteristics of adult patients with invasive pneumococcal disease (IPD) in Japan. METHODS: Data for 1722 adult patients with IPD were analyzed before (2017-2019) and during the COVID-19 pandemic (2020-2022). RESULTS: The seasonal influenza epidemic disappeared soon after the emergence of the pandemic. Compared with that before the pandemic (66.7%), we observed a lower bacteremic pneumonia proportion in patients with IPD during the pandemic (55.6%). The clinical presentations of IPD cases significantly differed between those with and without preceding influenza. The proportion of bacteremic pneumonia was higher in IPD patients with preceding influenza than in those without in both younger (44.9% vs 84.2%) and older adults (65.5% vs 87.0%) before the pandemic. The case fatality rate was significantly higher in IPD patients with preceding influenza (28.3%) than in those without (15.3%) in older adults before the pandemic (P = 0.020). Male and aging are high risk factors for death in older patients with IPD who had preceding influenza. CONCLUSION: Our study reveals that preceding seasonal influenza plays a role in the development of bacteremic pneumococcal pneumonia, increasing the risk of death in older adults.

Gut microbiota and metabolites in patients with COVID-19 are altered by the type of SARS-CoV-2 variant.

Introduction: Patients with COVID-19 have dysbiosis of the intestinal microbiota with altered metabolites in the stool. However, it remains unclear whether the differences among SARS-CoV-2 variants lead to differences in intestinal microbiota and metabolites. Thus, we compared the microbiome and metabolome changes for each SARS-CoV-2 variant in patients with COVID-19. Materials and methods: We conducted a multicenter observational study of patients with COVID-19 and performed fecal microbiome, metabolome, and calprotectin analyses and compared the results among the different SARS-CoV-2 variants. Results: Twenty-one patients with COVID-19 were enrolled and stratified according to the SARS-CoV-2 strain: six with the Alpha, 10 with the Delta, and five with the Omicron variant. Fecal microbiome analysis showed that α-diversity was reduced in the order of the Omicron, Delta, and Alpha variants (p = 0.07). Linear discriminant analysis revealed differences in the abundance of short-chain fatty acid-producing gut microbiota for each SARS-CoV-2 variant. Fecal metabolome analysis showed that the Omicron and Delta variants had markedly reduced propionic and lactic acid levels compared to the Alpha strain (p < 0.05). Conclusion: The intestinal microbiota of patients with COVID-19 varies depending on the SARS-CoV-2 variant. Dysbiosis of the intestinal microbiota due to differences in SARS-CoV-2 variants causes a decrease in intestinal short-chain fatty acids.

The impact of respiratory reactance in oscillometry on survival in patients with idiopathic pulmonary fibrosis.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) is a progressive disease with a poor prognosis. Pulmonary function tests (PFTs) aid in evaluating the disease status of IPF. The clinical significance of oscillometry measurements in interstitial lung diseases has recently been reported. Our previous study showed that respiratory reactance (Xrs) measured by oscillometry reflected disease severity and predicted subsequent lung capacity decline in patients with IPF. However, the direct impact of Xrs on survival needs to be determined, and there are currently no reference values in oscillometry to predict prognosis. Therefore, this study aimed to investigate the association between oscillometry measurements, particularly Xrs, and survival in patients with IPF and to determine the cutoff values of Xrs that predict 3-year survival. METHODS: We analyzed the relationship between the measured values of PFT and oscillometry derived from 178 patients with IPF. Univariate and multivariate Cox proportional hazards analyses were performed to investigate the relationships between clinical indices at the time of the first oscillometry and survival. We performed the time-dependent receiver operating characteristic (ROC) curve analysis to set the optimized cutoff values of Xrs for 3-year survival prediction. We examined the discriminating power of cutoff values of Xrs on survival using the Kaplan-Meier method and the log-rank test. RESULTS: Xrs components, especially in the inspiratory phase (In), significantly correlated with the PFT values. In the multivariate analyses, Xrs (all of reactance at 5 Hz [X5], resonant frequency [Fres], and low-frequency reactance area [ALX] in the inspiratory phase) had a significant impact on survival (X5, p = 0.003; Fres, p = 0.016; ALX, p = 0.003) independent of age, sex, and other prognostic factors derived from the univariate analysis. The area under the ROC curve was 0.765, 0.759, and 0.766 for X5 In, Fres In, and ALX In, with cutoff values determined at - 0.98, 10.67, and 5.32, respectively. We found significant differences in survival after dividing patients using each of the cutoff values of Xrs. CONCLUSIONS: In patients with IPF, Xrs measured by oscillometry significantly impacted survival. We also determined the cutoff values of Xrs to discriminate patients with poor prognoses.

Serum Testosterone Is Associated With the Severity of COVID-19.

BACKGROUND/AIM: Coronavirus disease 2019 (COVID-19) is more likely to be severe in men than in women. Its association with sex hormones as an aggravating factor for male patients has been attracting attention. This study aimed to investigate whether serum testosterone is associated with the aggravation of COVID-19. PATIENTS AND METHODS: Serum testosterone concentrations in 116 male patients with COVID-19 and residual serum were measured and examined upon their admission to Sapporo Medical University Hospital between February 1, 2020 and March 31, 2021. RESULTS: Blood samples collected from these patients with COVID-19 were analyzed. The serum testosterone levels were 2.19±1.35, 1.29±0.88, and 0.75±0.58 ng/ml in mild, moderate, and severe groups, respectively. Patients with severe COVID-19 on admission had lower testosterone levels (p<0.001). At a cutoff level of 1.31 ng/ml, the area under the curve for the comparison of severe with non-severe cases was 0.825. Furthermore, serum testosterone levels negatively correlated with C-reactive protein and serum amyloid A levels but positively correlated with calcium, zinc, C3, and C4. CONCLUSION: In male patients with COVID-19, low serum testosterone levels correlated with disease severity, accompanied by a strong inflammatory reaction and proportion of complement consumption.

Protective effect of Bifidobacterium longum BB536 against nausea caused by pirfenidone in a mouse model of pellagra.

Pellagra is caused by abnormal intake and/or use of nicotinic acid and is known in part to be induced by the use of medications such as isoniazid or pirfenidone. We previously investigated atypical phenotypes of pellagra, such as nausea, using a mouse model of pellagra and found that gut microbiota play an important role in the development of these phenotypes. Here, we investigated the effect of Bifidobacterium longum BB536 on pellagra-related nausea caused by pirfenidone in our mouse model. Our pharmacological data indicated that pirfenidone (PFD) causes modulation of the gut microbiota profile, which appeared to play an important role in the development of pellagra-related nausea. A gut microbiota-mediated protective effect of B. longum BB536 against nausea caused by PFD was also identified. Finally, the urinary ratio of nicotinamide/N-methylnicotinamide was shown to be a biomarker of pellagra-like adverse effects induced by PFD, and it may contribute to the prevention of these effects in patients with idiopathic pulmonary fibrosis.

The Soluble Lectin Families as Novel Biomarkers for COVID-19 Pneumonia.

BACKGROUND/AIM: The lung-specific soluble lectins, SP-A and SP-D have been clinically used to diagnose interstitial lung disease, but their clinical significance in COVID-19 remains controversial. This study was undertaken to determine their association with other lectins (MBL and FCN1), disease severity, and radiographs in COVID-19 patients. PATIENTS AND METHODS: A total of 131 patients with COVID-19 admitted in the Sapporo Medical University Hospital between May 22 and September 19, 2021, were enrolled in the study. Data including demographics, medical history, symptoms, signs, laboratory findings, and radiological images were collected from the patients' medical records. Chest computed tomography (CT) scanning was performed at admission. Serum levels of surfactant protein A and D (SP-A and SP-D), mannose-binding lectin (MBL) and ficolin1 (FCN1) were measured using enzyme-linked immunosorbent assay (ELISA) kits. RESULTS: Compared to the control group, the COVID-19 group had significantly higher serum SP-A and FCN1 levels on admission (SP-A: 59.60±38.89 vs. 35.61±11.22 ng/ml; p<0.01, FCN1: 542.45±506.04 vs. 250.6±161.1 ng/ml; p<0.01). The severe group in COVID-19 had significantly higher serum SP-D and lower MBL levels than the non-severe group (SP-D: 141.7±155.7 vs. 61.41±54.54 ng/ml; p<0.01, MBL: 1,670±1,240 vs. 2,170±1,140 ng/ml; p<0.05). SP-D strongly reflected the degree of imaging findings, whereas SP-A showed a significant correlation, albeit slightly weaker than SP-D. Conversely, MBL and FNC1 were not significantly correlated with imaging findings. CONCLUSION: Among soluble serum lectins, SP-A and SP-D may be more sensitive to CT findings than reported disease biomarkers such as IL-6, LDH, and CRP due to their lung-specific characteristics.

Development of a new HISCL automated CXCL9 immunoassay.

C-X-C motif chemokine ligand 9 (CXCL9), a candidate biomarker, reflects type 1 (T1) inflammation pathology. Here, we report the analytical performance and clinical characteristics of a new CXCL9 reagent for a fully automated immunoassay device. We evaluated the limits of blank, detection, and quantitation (LoQ) along with other efficacy parameters, and the ability of the assay to report patient health, COVID-19 status, and the presence of asthma and/or interstitial lung diseases (ILDs). The coefficient of variation for 5-day total precision using two instruments was 7% across two controls, serum, and plasma panels. LoQ of 2.2 pg/mL suggested the efficacy of the assay in detecting T1 inflammation in plasma or serum; no cross-reactivity or interference was observed. We identified high serum CXCL9 levels in samples from patients with acute COVID-19 infections (n = 57), chronic bird-related hypersensitivity pneumonitis (n = 61), asthma (n = 194), and ILDs (n = 84) compared to healthy individuals (< 39.0 pg/mL). Furthermore, CXCL9 levels increased with age in asthma patients, and an opposite trend was observed for T2 inflammatory factors. These results suggest the utility of the automated CXCL9 immunoassay for measuring CXCL9 in clinical samples and reflect its role in T1 inflammation.

Pseudo-outbreak of Mycobacterium lentiflavum at a general hospital in Japan.

BACKGROUND: Mycobacterium lentiflavum is a slow-growing nontuberculous mycobacterium that is widely distributed in soil and water systems, but it is sometimes pathogenic to humans. Although cases of M. lentiflavum infections are rare, 22 isolates of M. lentiflavum were identified at a single hospital in Japan. We suspected a nosocomial outbreak; thus, we conducted transmission pattern and genotype analyses. METHODS: Cases of M. lentiflavum isolated at Kushiro City General Hospital in Japan between May 2020 and April 2021 were analyzed. The patient samples and environmental culture specimens underwent whole-genome sequencing (WGS). Additionally, we retrospectively collected clinical data from patient medical records. RESULTS: Altogether, 22 isolates of M. lentiflavum were identified from sputum and bronchoalveolar lavage samples. Clinically, the instances with M. lentiflavum isolates were considered contaminants. In the WGS analysis, 19 specimens, including 18 patient samples and 1 environmental culture from the hospital's faucet, showed genetic similarity. The frequency of M. lentiflavum isolation decreased after we prohibited the use of taps where M. lentiflavum was isolated. CONCLUSIONS: WGS analysis identified that the cause of M. lentiflavum pseudo-outbreak was the water used for patient examinations, including bronchoscopy.

Factors affecting the sensitivity of quantitative severe acute respiratory syndrome coronavirus 2 antigen test.

INTRODUCTION: The accuracy of nucleic acid amplification tests (NAATs) is affected by various factors; however, studies examining the factors affecting the accuracy of quantitative severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen test (QAT) are limited. METHODS: A total of 347 nasopharyngeal samples were collected from patients with coronavirus disease 2019 (COVID-19), and the date of onset was obtained from the electronic medical records. The SARS-CoV-2 antigen level was measured using Lumipulse Presto SARS-CoV-2 Ag (Presto), while NAAT was performed using the Ampdirect 2019-nCoV Detection Kit. RESULTS: Presto had a sensitivity rate of 95.1% (95% confidence interval: 92.8-97.4) in detecting the SARS-CoV-2 antigen in 347 samples. The number of days from symptom onset to sample collection was negatively correlated with the amount of antigen (r = -0.515) and sensitivity of Presto (r = -0.711). The patients' age was lower in the Presto-negative samples (median age, 39 years) compared with that in the Presto-positive samples (median age, 53 years; p < 0.01). A significant positive correlation was observed between age (excluding teenagers) and Presto sensitivity (r = 0.764). Meanwhile, no association was found between the mutant strain, sex, and Presto results. CONCLUSION: Presto is useful for the accurate diagnosis of COVID-19 owing to its high sensitivity when the number of days from symptom onset to sample collection is within 12 days. Furthermore, age may affect the results of Presto, and this tool has a relatively low sensitivity in younger patients.

Invasive Haemophilus influenzae disease among adults in Japan during 2014-2018.

PURPOSE: We describe the epidemiology of invasive Haemophilus influenzae disease (IHD) among adults in Japan. METHODS: Data for 200 adult IHD patients in 2014-2018 were analyzed. The capsular type of H. influenzae was determined by bacterial agglutination and polymerase chain reaction (PCR), and non-typeable Haemophilus influenzae (NTHi) was identified by PCR. RESULTS: The annual incidence of IHD (cases per 100,000 population) was 0.12 for age 15-64 years and 0.88 for age ≥ 65 years in 2018. The median age was 77 years, and 73.5% were aged ≥ 65 years. About one-fourth of patients were associated with immunocompromising condition. The major presentations were pneumonia, followed by bacteremia, meningitis and other than pneumonia or meningitis (other diseases). The case fatality rate (CFR) was 21.2% for all cases, and was significantly higher in the ≥ 65-year group (26.1%) than in the 15-64-year group (7.5%) (p = 0.013). The percentage of cases with pneumonia was significantly higher in the ≥ 65-year group than in the 15-64-year group (p < 0.001). The percentage of cases with bacteremia was significantly higher in the 15-64-year group than in the ≥ 65-year group (p = 0.027). Of 200 isolates, 190 (95.0%) were NTHi strains, and the other strains were encapsulated strains. 71 (35.5%) were resistant to ampicillin, but all were susceptible to ceftriaxone. CONCLUSION: The clinical presentations of adult IHD patients varied widely; about three-fourths of patients were age ≥ 65 years and their CFR was high. Our findings support preventing strategies for IHD among older adults, including the development of NTHi vaccine.

Analysis of diagnostic performance and factors causing nonspecific reactions in SARS-CoV-2 rapid antigen detection tests.

INTRODUCTION: Early diagnosis and appropriate infection control are important to prevent the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this study, we aimed to assess the diagnostic performance of SARS-CoV-2 rapid antigen detection (RAD) tests and the factors that cause nonspecific reactions. METHODS: Nasopharyngeal swab specimens (n = 100), sputum specimens (n = 10), and lithium-heparin plasma samples (n = 100) were collected. We evaluated Espline®SARS-CoV-2 (Espline) and SARS-CoV-2 Rapid Antigen Test that also known as STANDARD Q® (STANDARD Q), with reverse transcription-polymerase chain reaction (RT-PCR) and Lumipulse® Presto SARS-CoV-2 Ag as reference tests. In addition, we investigated the effects of inadequate pretreatment methods and five potential causes of nonspecific reactions. RESULTS: The sensitivities of Espline and STANDARD Q were 60% and 57%, respectively, and their specificity was 100%. It was confirmed that the judgment line for the positive insufficiently mixed specimens was faint. A false-positive result was observed with STANDARD Q when sputum was used as a specimen to investigate judgment the effect of viscosity. CONCLUSIONS: Espline and STANDARD Q show good sensitivity for specimens with Ct values less than 25, but specimens collected within 9 days of symptom onset may still give false negatives. The test should be performed carefully, and the results should be judged comprehensively, taking into account clinical symptoms and patient background.

Deep-learning algorithm to detect fibrosing interstitial lung disease on chest radiographs.

BACKGROUND: Antifibrotic therapies are available to treat chronic fibrosing interstitial lung diseases (CF-ILDs), including idiopathic pulmonary fibrosis. Early use of these treatments is recommended to slow deterioration of respiratory function and to prevent acute exacerbation. However, identifying patients in the early stages of CF-ILD using chest radiographs is challenging. In this study, we developed and tested a deep-learning algorithm to detect CF-ILD using chest radiograph images. METHOD: From the image archive of Sapporo Medical University Hospital, 653 chest radiographs from 263 patients with CF-ILDs and 506 from 506 patients without CF-ILD were identified; 921 were used for deep learning and 238 were used for algorithm testing. The algorithm was designed to output a numerical score ranging from 0 to 1, representing the probability of CF-ILD. Using the testing dataset, the algorithm's capability to identify CF-ILD was compared with that of doctors. A second dataset, in which CF-ILD was confirmed using computed tomography images, was used to further evaluate the algorithm's performance. RESULTS: The area under the receiver operating characteristic curve, which indicates the algorithm's detection capability, was 0.979. Using a score cut-off of 0.267, the sensitivity and specificity of detection were 0.896 and 1.000, respectively. These data showed that the algorithm's performance was noninferior to that of doctors, including pulmonologists and radiologists; performance was verified using the second dataset. CONCLUSIONS: We developed a deep-learning algorithm to detect CF-ILDs using chest radiograph images. The algorithm's detection capability was noninferior to that of doctors.

Analysis of real-world data and a mouse model indicates that pirfenidone causes pellagra.

Background: Pirfenidone (PFD) is widely used in patients with idiopathic pulmonary fibrosis (IPF) and its adverse effects, such as nausea and photosensitivity, are well known. Many patients with IPF have reduced doses or even cessation of PFD because of its side-effects. No solutions have been found for these side-effects because the current mechanistic insights are insufficient. Methods: Using the results of real-world data analysis from the US Food and Drug Administration Adverse Events Reporting System, we hypothesised that PFD-related symptoms may be similar to pellagra. Reverse translational experiments using female BALB/c mice were performed to validate and estimate this hypothesis. Niacin and its metabolite responses were compared between patients with IPF treated with PFD and those treated without PFD. Results: The pellagra hypothesis was translated from real-world data analysis. Pharmacological and comprehensive genetic investigations showed that PFD caused pellagra-related nausea and photosensitivity in a mouse model, which may have been mediated by the actions of nicotinamide N-methyltransferase (NNMT). Higher NNMT substrate responses were observed in urine from patients and mice with PFD than in those without PFD. Conclusions: PFD may cause pellagra or pellagra-like symptoms such as photosensitivity. Further studies are required to investigate whether niacin prevents pellagra-like symptoms caused by PFD in patients with IPF.

Pneumocystis jirovecii Pneumonia Associated with COVID-19 in Patients with Interstitial Pneumonia.

Here, we report two cases of patients with interstitial pneumonia (IP) on steroids who developed Pneumocystis jirovecii pneumonia (PJP) following coronavirus disease 2019 (COVID-19) infection. Case 1: A 69-year-old man on 10 mg of prednisolone (PSL) daily for IP developed new pneumonia shortly after his COVID-19 infection improved and was diagnosed with PJP based on chest computed tomography (CT) findings and elevated serum ß-D-glucan levels. Trimethoprim-sulfamethoxazole (TMP-SMZ) was administered, and the pneumonia resolved. Case 2: A 70-year-old woman taking 4 mg/day of PSL for IP and rheumatoid arthritis developed COVID-19 pneumonia, which resolved mildly, but her pneumonia flared up and was diagnosed as PJP based on CT findings, elevated ß-D-glucan levels, and positive polymerase chain reaction for P. jirovecii DNA in the sputum. The autopsy revealed diffuse alveolar damage, increased collagen fiver and fibrotic foci, mucinous component accumulation, and the presence of a P. jirovecii cyst. In conclusion, steroids and immunosuppressive medications are well-known risk factors for PJP. Patients with IP who have been taking these drugs for a long time are frequently treated with additional steroids for COVID-19; thus, PJP complications should be avoided in such cases.

Study of post-opening stability of active ingredients in hand sanitizers.

INTRODUCTION: Hand disinfection plays an important role in infection control. Currently, hand sanitizers containing ethanol and chlorhexidine gluconate as active ingredients are widely used. Most of hand sanitizers have a defined expiration date for use. However, there was no rule about the expiration date after opening defined with the evidence. Therefore, we examined the fluctuation of active ingredients and disinfection effect after opening the bottle. METHOD: Twelve hand sanitizers from 44 to 921 days after opening set in different places in the hospital were examined and unopened hand sanitizer used as a control. Chlorhexidine gluconate and ethanol of each samples were measured by high performance liquid chromatography and gas chromatography, respectively. The correlation between the concentration of each ingredient obtained and the number of days after opening, bottle weight, storage temperature and humidity was analyzed. A time-kill test based on ASTM E2315-03 was performed to confirm the actual disinfection effect. RESULTS: It was observed that active ingredients had not been decreased up to 921 days after opening and were not affected by storage conditions after opening. In addition, a decrease of disinfection effect was not observed in any sample. CONCLUSIONS: We found that hand sanitizers do not need to be discard after a number of days have passed because the active ingredients are retained even after opening in it.

Genotypes and transmission routes of noroviruses causing sporadic acute gastroenteritis among adults and children, Japan, 2015-2019.

Noroviruses (NoVs) are major causes of acute viral gastroenteritis at all ages worldwide. The molecular epidemiology of sporadic cases remains poorly understood, especially in adults. Additionally, no studies have analyzed the transmission route in sporadic acute gastroenteritis. In this study, we investigated cases of very mild sporadic NoV acute gastroenteritis in adults (medical staff) who do not visit the outpatient clinic and child outpatients. We also evaluated genotype differences between adults and children and possible transmission routes in adults during 5 years. The number of NoV positives were 58 in adults and 124 in children. In adults, the NoV positivity rate in this study was higher (64.4%) than that in previous reports of outpatients (10%) and inpatients (5%) in the United State. This finding suggested that the NoV positivity rate might be high in adults with very mild acute gastroenteritis. In adults, human-to-human transmission rates from children and food-borne transmission (raw oysters) were 21.6% (11/51) and 19.6% (10/51), respectively. Among adults, GII.2, GII.4, and GII.17 were the predominant genotypes, with rates of 32.7%, 30.9%, and 21.8%, respectively. Among children, GII.4 and GII.2 were the predominant genotypes, with rates of 45.5% and 40.6%, respectively. GII.17 was only detected in 0.8% (1/123) of children. Trends in NoV genotypes are expected to differ depending on the patient's age. Investigating sporadic cases including the patient's background (age and transmission route) may be helpful to monitor the trend of NoV strains, forecast prevalent NoV GII genotypes, and develop NoV vaccines.

Viral load may impact the diagnostic performance of nasal swabs in nucleic acid amplification test and quantitative antigen test for SARS-CoV-2 detection.

INTRODUCTION: Compared to nasopharyngeal swabs (NPS), there has been insufficient evaluation of the diagnostic performance of nasal swabs (NS) for the detection of severe acute respiratory coronavirus 2 (SARS-CoV-2) in the nucleic acid amplification test (NAAT) and quantitative SARS-CoV-2 antigen test (QAT). METHODS: We prospectively compared healthcare worker-collected and flocked NS within nine days after symptom onset to paired NPS to detect SARS-CoV-2 in NAAT and QAT on the fully automated Lumipulse system. The agreement between sample types was evaluated, and cycle threshold (Ct) values and antigen levels were used as surrogate viral load measures. RESULTS: Sixty sets of NPS and NS samples were collected from 40 patients with COVID-19. The overall agreements between NAAT and QAT samples were 76.7% and 65.0%, respectively. In NAAT, the Ct value of NS was significantly higher, 5.9, than that of NPS. Thirty-nine (95.1%) NS tested positive in 41 positive-paired NPS with Ct ≤ 30. The negative correlation was observed between antigen levels of NS in QAT and Ct values of NS in NAAT (r = -0.88). In QAT, the antigen level of NS was significantly lower than that of NPS. Thirty-six (90.0%) NS tested positive in 40 positive-paired NPS with antigen levels >100 pg/mL, which were collected significantly earlier than those with antigen levels ≤100 pg/mL. CONCLUSIONS: In NAAT and QAT, NS had limited performance in detecting SARS-CoV-2 compared to NPS. However, NS may be helpful for patients with COVID-19 with high viral loads or those in the early stages of the illness.

Impaired tryptophan metabolism in the gastrointestinal tract of patients with critical coronavirus disease 2019.

Introduction: Coronavirus disease 2019 (COVID-19) is still causing a global pandemic. But the mechanism of COVID-19 severity is not well elucidated. Materials and methods: We conducted two single-center observational studies of patients with COVID-19. In the first study, the enrolled patients were distinguished based on critical vs. non-critical COVID-19. We collected blood samples from the patients at admission to measure markers related to inflammation and thrombosis and stool samples to analyze the fecal microbiome, metabolome, and calprotectin level. In the second study, we collected ileum and colon tissue samples from patients with critical COVID-19 who required colonoscopy due to severe gastrointestinal symptoms and analyzed mucosal gene expression. Results: A total of 19 blood samples and 10 stool samples were collected. Interleukin (IL)-6 was the only serum inflammatory marker with significantly higher levels in the critical group than in the non-critical group. The fecal calprotectin level in the critical group was significantly higher than that in the non-critical group (P = 0.03), regardless of the presence of gastrointestinal symptoms. Stool metabolomic analysis showed that the level of indole-3-propionic acid, a ligand for aryl hydrocarbon receptor (AhR), was markedly decreased in the critical group compared to that in the non-critical group (P = 0.01). The expression of genes involved in tryptophan metabolism, including ACE2, AHR, CARD9, and IL22, was downregulated in the ileum of critical COVID-19 patients who required a colonoscopy. Discussion: Critical COVID-19 patients have gastrointestinal inflammation potentially caused by impaired tryptophan metabolism in the small intestine due to decreased expression of genes involved in tryptophan metabolism.

Role of transient receptor potential vanilloid 4 in therapeutic antifibrotic effects of pirfenidone.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fatal lung disorder characterized by aberrant extracellular matrix deposition in the interstitium. Pirfenidone is an antifibrotic agent used to treat patients with IPF. Pirfenidone shows a pleiotropic mode of action, but its underlying antifibrotic mechanism is unclear. Transient receptor potential vanilloid 4 (TRPV4), which is a mechanosensitive calcium channel, was recently shown to be related to pulmonary fibrosis. To clarify the antifibrotic mechanisms of pirfenidone, we investigated whether TRPV4 blockade has a pharmacological effect in a murine model of pulmonary fibrosis and whether pirfenidone contributes to suppression of TRPV4. Our synthetic TRPV4 antagonist and pirfenidone treatment attenuated lung injury in the bleomycin mouse model. TRPV4-mediated increases in intracellular calcium were inhibited by pirfenidone. In addition, TRPV4-stimulated interleukin-8 release from cells was reduced and a delay in cell migration was abolished by pirfenidone. Furthermore, pirfenidone decreased TRPV4 endogenous ligands in bleomycin-administered mouse lungs and their production by microsomes of human lungs. We found TRPV4 expression in the bronchiolar and alveolar epithelium and activated fibroblasts of the lungs in patients with IPF. Finally, we showed that changes in forced vital capacity of patients with IPF treated with pirfenidone were significantly correlated with metabolite levels of TRPV4 endogenous ligands in bronchoalveolar lavage fluid. These results suggest that the antifibrotic action of pirfenidone is partly mediated by TRPV4 and that TRPV4 endogenous ligands in bronchoalveolar lavage fluid may be biomarkers for distinguishing responders to pirfenidone.