Kodai Nishi

An aspergilloma is a fungus ball that forms within a preexisting cavity, most commonly in the lungs but also in the paranasal sinuses. It represents a chronic inflammatory disorder that can persist for months and cause life-threatening hemoptysis. In this study, we hypothesized that the fungus ball is predominantly composed of non-viable hyphae and that chronic inflammation is maintained primarily by host responses to these non-viable elements rather than by ongoing fungal proliferation. To investigate this, we created a murine fungus ball model by implanting heat-killed Aspergillus fumigatus fungus balls, allowing for ≥16 weeks of longitudinal assessment. The model recapitulated key pathological features of the human disease, including progressive fibrosis and sustained angiogenesis, coinciding with elevated vascular endothelial growth factor (VEGF). A distinct immune response was observed where neutrophils infiltrated the fungus ball core, while macrophages accumulated at the periphery. Strikingly, these macrophages surrounding the lesion progressively became lipid-laden foam-like cells with an M1-skewed profile, a phenomenon reproduced in vitro by exposure to non-viable hyphae alone. Thus, the fungal material itself can sustain chronic inflammation and vascular remodeling, implicating macrophage lipid accumulation as a process potentially contributing to the chronic host response. These findings highlight lipid dysregulation and failed fungal clearance as key features of the host-response disorder associated with the fungus ball and establish a tractable platform for evaluating host-directed therapies. IMPORTANCE: Aspergilloma, a fungus ball that forms in preexisting cavities of the lung or paranasal sinuses, can cause chronic symptoms and life-threatening bleeding. Current fungicidal treatments, including antifungals, are often ineffective, and surgery to remove the fungal ball is risky. To better understand why these lesions can persist even when active fungal growth is limited, we developed a murine subcutaneous fungus ball model using non-viable Aspergillus fumigatus . In this model, a fungal mass composed largely of non-viable hyphae was associated with chronic inflammation, neovascularization, fibrosis, and the accumulation of lipid-laden, foam cell-like macrophages around the fungus ball. These findings support the concept that persistent non-viable fungal material can sustain key features of aspergilloma-like pathology through dysregulated host responses. They provide a conceptual rationale for future studies of host-directed strategies that modulate inflammatory and lipid-handling pathways in addition to conventional antifungal approaches.

Background/Objectives: Epidemiological and clinical studies have linked both hypothyroidism and hyperthyroidism to adverse cardiac outcomes, including heart failure and myocardial fibrosis. Triiodothyronine (T3), a biologically active thyroid hormone, is important for cardiovascular homeostasis. While the effects of physiological and non-physiological T3 levels on cardiomyocytes have been extensively investigated, the impact of hypothyroidism and hyperthyroidism on cardiac stromal cells (CSCs), which constitute the majority of the cells in the heart, remains understudied. Given CSCs’ essential role in extracellular matrix (ECM) remodeling and paracrine signaling, understanding their response to altered T3 states is necessary to fully elucidate the thyroid hormone-induced cardiac responses. Methods: Cardiac stromal cells were isolated from human atrial appendages and cultured under hypothyroid (0 nM T3), euthyroid (2.5 nM T3), and hyperthyroid (25 nM T3) conditions for 24 (short term) and 120 h (long term). The cells were harvested after 24 h of treatment using trypsin and automatically counted, and their ECM-related gene and growth factor expression levels were assessed using quantitative RT-PCR. Cardiac glucose uptake in hypothyroid, euthyroid, and hyperthyroid mice was monitored using [18F]-FDG PET/CT at acute (7 days) and chronic (42 days) time points. Results: Both hypo- and hyperthyroidism significantly increased the number of CSCs harvested after 24 h. There were acute alterations in the expression of the ECM-related genes COL1A1, COL3A1, TIMP3 (p < 0.05), and TIMP1 (p < 0.01). Similarly, growth factors such as PDGF-A (p < 0.001), TGF-b, and IGF1 (p < 0.05) were transiently upregulated under non-physiological T3 conditions, especially hypothyroidism. Most of these alterations were attenuated or reversed at the 120 h time point. In vivo PET imaging revealed significant increases in cardiac glucose uptake under acute hypothyroidism (p < 0.05) and decreases under acute hyperthyroidism (p < 0.05). However, these metabolic shifts normalized with chronic exposure, paralleling the transient nature of the gene expression changes observed in vitro. Conclusions: Non-physiological T3 concentrations induce proliferation and changes in ECM-related and growth factor gene expression in CSCs. Most of these changes are acute and return to normal levels after chronic exposure. These transient cellular responses correlate closely with the cardiac metabolic response patterns to acute and chronic hypothyroidism and hyperthyroidism.

No effective vaccines or treatments are currently available for severe fever with thrombocytopenia syndrome (SFTS), a fatal tick-borne infectious disease caused by the SFTS virus (SFTSV). This study evaluated the potential of ¹¹¹In-labeled anti-SFTSV antibodies targeting SFTSV structural proteins as single-photon emission computed tomography (SPECT) imaging agents for the selective visualization of SFTSV-infected sites. This study used nuclear medicine imaging to elucidate the pathology of SFTS and assess its therapeutic efficacy. Immunostaining experiments confirmed that the anti-SFTSV antibody (N-mAb), which targets the N protein, specifically accumulated in SFTSV-infected Vero E6 cells. ¹¹¹In-labeled N-mAb was successfully prepared using a diethylenetriaminepentaacetic acid (DTPA) chelator, resulting in [¹¹¹In]In-DTPA-N-mAb with high radiochemical purity exceeding 95% and a radiochemical yield of 55%. Cell-binding assays using SFTSV-infected Vero E6 cells demonstrated that [¹¹¹In]In-DTPA-N-mAb binding was detectable even without membrane permeabilization, with the binding intensity correlating with infection levels. In vivo studies using SFTSV-infected A129 mice showed high spleen accumulation of [¹¹¹In]In-DTPA-N-mAb (87.5% ID/g), consistent with SFTSV tropism, compared to 12.3% ID/g in mock-infected mice. SPECT/CT imaging clearly revealed high radioactivity in these regions. Although nonspecific accumulation was noted in the liver and spleen, this issue may be mitigated through antibody modifications such as fragmentation or PEGylation. Overall, [¹¹¹In]In-DTPA-N-mAb is a promising imaging agent for non-invasive visualization of SFTSV-infected sites and may aid in elucidating SFTS pathology and assessing therapeutic efficacy.

The World Health Organization has cautioned that antimicrobial resistance (AMR) will be responsible for an estimated 10 million deaths annually by 2050. To facilitate prompt and accurate diagnosis and treatment of infectious disease, we investigated the potential of amino acids for use as indicators of bacterial growth activity by clarifying which amino acids are taken up by bacteria during the various growth phases. In addition, we examined the amino acid transport mechanisms that are employed by bacteria based on the accumulation of labeled amino acids, Na⁺ dependence, and inhibitory effects using a specific inhibitor of system A. We found that ³H-L-Ala accurately reflects the proliferative activity of Escherichia coli K-12 and pathogenic EC-14 in vitro. This accumulation in E. coli could be attributed to the amino acid transport systems being different from those found in human tumor cells. Moreover, biological distribution assessed in infection model mice with EC-14 using ³H-L-Ala showed that the ratio of ³H-L-Ala accumulated in infected muscle to that in control muscle was 1.20. By detecting the growth activity of bacteria in the body that occurs during the early stages of infection by nuclear imaging, such detection methods may result in expeditious diagnostic treatments for infectious diseases.

We evaluated the whole-body distribution of orally-administered radioiodine-125 labeled acetaminophen (¹²⁵I-AP) to estimate gastrointestinal absorption of anionic drugs. ¹²⁵I-AP was added to human embryonic kidney (HEK)293 and Flp293 cells expressing human organic anion transporting polypeptide (OATP)1B1/3, OATP2B1, organic anion transporter (OAT)1/2/3, or carnitine/organic cation transporter (OCTN)2, with and without bromosulfalein (OATP and multidrug resistance-associated protein (MRP) inhibitor) and probenecid (OAT and MRP inhibitor). The biological distribution in mice was determined by oral administration of ¹²⁵I-AP with and without bromosulfalein and by intravenous administration of ¹²⁵I-AP. The uptake of ¹²⁵I-AP was significantly higher in HEK293/OATP1B1, OATP1B3, OATP2B1, OAT1, and OAT2 cells than that in mock cells. Bromosulfalein and probenecid inhibited OATP- and OAT-mediated uptake, respectively. Moreover, ¹²⁵I-AP was easily excreted in the urine when administered intravenously. The accumulation of ¹²⁵I-AP was significantly lower in the blood and urinary bladder of mice receiving oral administration of both ¹²⁵I-AP and bromosulfalein than those receiving only ¹²⁵I-AP, but significantly higher in the small intestine due to inhibition of OATPs and/or MRPs. This study indicates that whole-body distribution after oral ¹²⁵I-AP administration can be used to estimate gastrointestinal absorption in the small intestine via OATPs, OATs, and/or MRPs by measuring radioactivity in the urinary bladder.

Drug metabolizing enzyme activity is affected by various factors such as drug–drug interactions, and a method to quantify drug metabolizing enzyme activity in real time is needed. In this study, we developed a novel radiopharmaceutical for quantitative imaging to estimate hepatic CYP3A4 and CYP2D6 activity. Iodine-123- and 125-labeled O-desmethylvenlafaxine (^123/125I-ODV) was obtained with high labeling and purity, and its metabolism was found to strongly involve CYP3A4 and CYP2D6. SPECT imaging in normal mice showed that the administered ¹²³I-ODV accumulated early in the liver and was excreted into the gallbladder, as evaluated by time activity curves. In its biological distribution, ¹²⁵I-ODV administered to mice accumulated early in the liver, and only the metabolite of ¹²⁵I-ODV was quickly excreted into the bile. In CYP3A4- and CYP2D6-inhibited model mice, the accumulation in bile decreased more than in normal mice, indicating inhibition of metabolite production. These results indicated that imaging and quantifying the accumulation of radioactive metabolites in excretory organs will aid in determining the dosages of various drugs metabolized by CYP3A4 and CYP2D6 for individualized medicine. Thus, ^123/125I-ODV has the potential to direct, comprehensive detection and measurement of hepatic CYP3A4 and CYP2D6 activity by a simple and less invasive approach.

In this study, we evaluated the use of 15-(4-¹²³I-iodophenyl)-3(R,S)-methylpentadecanoic acid (¹²³I-BMIPP) to visualize fatty acid metabolism in bacteria for bacterial infection imaging. We found that ¹²³I-BMIPP, which is used for fatty acid metabolism scintigraphy in Japan, accumulated markedly in Escherichia coli EC-14 similar to ¹⁸F-FDG, which has previously been studied for bacterial imaging. To elucidate the underlying mechanism, we evaluated changes in ¹²³I-BMIPP accumulation under low-temperature conditions and in the presence of a CD36 inhibitor. The uptake of ¹²³I-BMIPP by EC-14 was mediated via the CD36-like fatty-acid-transporting membrane protein and accumulated by fatty acid metabolism. In model mice infected with EC-14, the biological distribution and whole-body imaging were assessed using ¹²³I-BMIPP and ¹⁸F-FDG. The ¹²³I-BMIPP biodistribution study showed that, 8 h after infection, the ratio of ¹²³I-BMIPP accumulated in infected muscle to that in control muscle was 1.31 at 60 min after ¹²³I-BMIPP injection. In whole-body imaging 1.5 h after ¹²³I-BMIPP administration and 9.5 h after infection, infected muscle exhibited a 1.33-times higher contrast than non-infected muscle. Thus, ¹²³I-BMIPP shows potential for visualizing fatty acid metabolism of bacteria for imaging bacterial infections.

The effectiveness of L- and D-amino acids for detecting the early stage of infection in bacterial imaging was compared. We evaluated the accumulation of ³H-L-methionine (Met), ³H-D-Met, ³H-L-alanine (Ala), and ³H-D-Ala in E. coli EC-14 and HaCaT cells. Biological distribution was assessed in control and lung-infection-model mice with EC-14 using ³H-L- and D-Met, and ¹⁸F-FDG. A maximum accumulation of ³H-L- and D-Met, and ³H-L- and D-Ala occurred in the growth phase of EC-14 in vitro. The accumulation of ³H-L-Met and L-Ala was greater than that of ³H-D-Met and D-Ala in both EC-14 and HaCaT cells. For all radiotracers, the accumulation was greater in EC-14 than in HaCaT cells at early time points. The accumulation was identified at 5 min after injection in EC-14, whereas the accumulation gradually increased in HaCaT cells over time. There was little difference in biodistribution between ³H-L-and D-Met except in the brain. ³H-L- and D-Met were sensitive for detecting areas of infection after the spread of bacteria throughout the body, whereas ¹⁸F-FDG mainly detected primary infection areas. Therefore, ¹¹C-L- and D-Met, radioisotopes that differ only in terms of ³H labeling, could be superior to ¹⁸F-FDG for detecting bacterial infection in lung-infection-model mice.

Gastrointestinal tract absorption of cationic anticancer drugs and medicines was estimated using whole-body imaging following oral [¹²³I]MIBG administration. [¹²³I]MIBG was added to cultures of human embryonic kidney (HEK)293 cells expressing human organic anion transporting polypeptide (OATP)2B1, carnitine/organic cation transporter (OCTN)1 and OCTN2, and organic cation transporter (OCT)1, OCT2, and OCT3 with and without cimetidine (an OCTN and OCT inhibitor) and L-carnitine (an OCTN inhibitor). Biodistribution analyses and single-photon emission computed tomography (SPECT) imaging in normal and dextran sodium sulfate (DSS)-induced experimental colitis mice were conducted using [¹²³I]MIBG with and without cimetidine. [¹²³I]MIBG uptake was significantly higher in HEK293/OCTN1, 2, and OCT1-3 cells than in mock cells. Uptake via OCTN was inhibited by L-carnitine, whereas OCT-mediated uptake was inhibited by cimetidine. Biodistribution analyses and SPECT imaging studies showed significantly lower accumulation of [¹²³I]MIBG in the blood, heart, liver, and bladder in DSS-induced experimental colitis mice and mice with cimetidine loading compared with normal mice, whereas significantly higher accumulation in the stomach and kidney was observed after [¹²³I]MIBG injection. [¹²³I]MIBG imaging after oral administration can be used to estimate gastrointestinal absorption in the small intestine via OCTN and/or OCT by measuring radioactivity in the heart, liver, and bladder.

The accumulation of high levels of ^99mTc-tetrofosmin (^99mTc-TF) in the hepatobiliary system can lead to imaging artifacts and interference with diagnosis. The present study investigated the transport mechanisms of ^99mTc-TF and attempted to apply competitive inhibition using a specific inhibitor to reduce ^99mTc-TF hepatic accumulation. In this in vitro study, ^99mTc-TF was incubated in HEK293 cells expressing human organic anion transporting polypeptide 1B1 (OATP1B1), OATP1B3, OATP2B1, organic anion transporter 2 (OAT2), organic cation transporter 1 (OCT1), OCT2, and Na⁺-taurocholate cotransporting polypeptide with or without each specific inhibitor to evaluate the contribution of each transporter to ^99mTc-TF transportation. In vivo studies, dynamic planar imaging, and single photon emission computed tomography (SPECT) experiments with rats were performed to observe alterations to ^99mTc-TF pharmacokinetics using cimetidine (CMT) as an OCT1 inhibitor. Time–activity curves in the liver and heart were acquired from dynamic data, and the ^99mTc-TF uptake ratio was calculated from SPECT. From the in vitro study, ^99mTc-TF was found to be transported by OCT1 and OCT2. When CMT-preloaded rats and control rats were compared, the hepatic accumulation of the ^99mTc-TF was reduced, and the time to peak heart count shifted to an earlier stage. The hepatic accumulation of ^99mTc-TF was markedly suppressed, and the heart-to-liver ratio increased 1.6-fold. The pharmacokinetics of ^99mTc-TF were greatly changed by OCT1 inhibitor. Even in humans, the administration of OCT1 inhibitor before cardiac SPECT examination may reduce ^99mTc-TF hepatic accumulation and contribute to the suppression of artifacts and the improvement of SPECT image quality.