Search Results (37)

Background and Objectives: The worldwide incidence of renal cell carcinoma (RCC) rose by 22% between 2012 and 2022. In Australia, RCC accounted for 2.8% of all cancer diagnoses and contributing to 1.8% of cancer-related deaths. Identification of RCC biomarkers may aid in diagnosis and management. Methods: A systematic review of immunohistochemical markers of RCC studies published between 1990 and 2019 was undertaken to select candidate biomarkers of RCC. Immunohistochemical staining of 73 clear cell RCC tumors and paired normal tissue was undertaken using selected markers. Semi-quantitative and quantitative analysis of staining intensity between paired samples was undertaken to evaluate utility as potential biomarkers, using Chi-square tests and paired t-tests for analysis. As an exploratory analysis, staining intensity was also compared on clinical/demographic variables using linear and logistic regression. Results: There were 123 candidate biomarkers identified in 91 studies. Four candidate markers were selected for further investigation: aminopeptidase A (APA)/cluster of differentiation (CD)249, aminopeptidase N (APN)/CD13, gamma-glutamyl transferase (GGT), and neuron-specific enolase (NSE). APA, GGT, and APN all demonstrated reduced staining intensity in the tumor compared with normal tissue (p < 0.001 for all). NSE demonstrated a statistically significant increase in expression in tumor compared with normal tissue (p < 0.001), and this was more pronounced in patients aged >60 years (p = 0.038). Conclusions: The utility of APA, APN, and GGT as diagnostic biomarkers in clear cell RCC is limited. NSE may have some role as a biomarker for clear cell RCC, particularly among older patients; however, further investigation is required. Full article

Aminopeptidase N (APN), an enzyme expressed in the small intestinal mucosa, is involved in dietary protein digestion. Previous studies have shown that oral administration of fermented milk containing lactic acid bacteria (LAB) enhances mucosal APN activity in young mice. This study aimed to investigate whether LAB strains stimulate mucosal APN activity in aged mice and to evaluate its relevance to age-related changes in body composition. The underlying molecular mechanisms were also explored in vitro. Experiment 1: Aged C57BL/6J mice were fed diets supplemented with heat-killed LAB strains—Enterococcus faecalis OU-23 (EF), Leuconostoc mesenteroides OU-03 (LM), or Lactiplantibacillus plantarum SNK12 (LP). Compared to the aged Control group, the ileal APN activity was significantly higher in the LP group. LP administration also elevated serum Gla-osteocalcin levels and decreased serum CTX-1 levels. Experiment 2: IEC-6 cells were co-cultured with LP that had been treated with RNase, DNase, or lysozyme. APN activity was significantly lower in cells co-cultured with DNase- or lysozyme-treated LP compared to those co-cultured with untreated LP. A specific LAB strain may enhance mucosal APN activity in the aged intestine, potentially contributing to improved bone metabolism. This effect may be mediated by bacterial DNA and peptidoglycan. Full article

6-monoacetylmorphine (6-MAM), a primary active metabolite of heroin that reaches the human brain, plays a crucial role in producing heroin-associated physiological and lethal effects. Therefore, 6-MAM has emerged as a key target for alleviating the adverse consequences of heroin abuse. In this study, the proposed 6-MAM hydrolase E. coli aminopeptidase N (eAPN) was recombinantly produced, and its biochemical and functional profiles were investigated. eAPN’s biochemical properties, with respect to pH, metal ions, and temperature, and catalytic functions toward peptidase substrates and 6-MAM were thoroughly examined. Extensive experiments reveal that incorporation of an N-terminal His-tag notably affects eAPN’s aminopeptidase activity. This cost-effective recombinant eAPN exhibits favorable thermostability and optimal activity at pH 7.5. Kinetic analysis toward peptidase substrates reveals that eAPN preferentially cleaves peptides following amino acid residues in the order of Ala > Arg >> Met, Gly > Leu > Pro, indicating a preference for small or basic amino acid residues as substrates. Computational and experimental studies have, for the first time, discovered that eAPN is capable of catalyzing the hydrolysis of heroin and 6-MAM, which has shed light on its functional versatility and potential applications. This work elucidates the biochemical properties of eAPN and expands its catalytic functions, thereby laying the groundwork for a deep understanding and further reengineering of eAPN to enhance its activity toward 6-MAM for heroin detoxification. Full article

Enterotoxigenic Escherichia coli (ETEC) is one of the primary pathogens causing diarrhea in piglets, causing significant economic losses in the swine farming industry. Due to the numerous serotypes of ETEC, traditional vaccines fail to provide sufficient cross-protection, and subunit vaccines based on epitope design have emerged as a safer and more effective approach for prevention and control. Unlike vaccine development strategies that involve the tandem arrangement of multiple antigenic epitopes, this study used the K88-FaeG protein as a backbone and incorporated the antigenic epitopes of K99-FanC to achieve a better immunogenicity. By using bioinformatics software to predict B-cell linear epitopes (score of over 0.6), B-cell epitopes from three-dimensional structures (50% amino acid score of ≥0.2), and B-cell epitope IgG antibody subtypes, as well as docking analysis with Sus scrofa aminopeptidase N (APN) receptors, six antigenic epitopes of K99-FanC were selected. Through Western blotting and competitive ELISA, we confirmed that all six recombinant proteins exhibited binding capabilities to K88- and K99-positive serum. The ELISA results showed that the serum levels of specific IgG and IgA antibodies increased after immunization, with FaeG-Ep3 and FaeG-Ep5 inducing the highest antibody titers against FanC-IgG (Log2 = 14.96) and FaeG-IgG (Log2 = 17.96), respectively. Bacterial adhesion assays revealed that only FaeG-Ep3 effectively blocked the adhesion of both K99 and K88 to IPEC-J2 cells. Immunization challenge experiments showed that, in the unimmunized group, mice infected with K88 and K99 experienced weight loss (p < 0.05) with intestinal villus shedding and intestinal wall structural damage. However, in the FaeG-Ep3-immunized group, no significant weight loss occurred after infection, and the villus protection rate (83%) was the same as that in the FaeG and FanC immunized groups. Overall, the FaeG-Ep3 recombinant protein identified in this study shows potential vaccine application value and provides new insights for developing multivalent vaccines against ETEC. Full article

The role of the yolk sac membrane (YSM) and digestive tract in the processing of egg yolk proteins during embryogenesis is unexplored in the duck Anas platyrhynchos domestica. Here, we investigated in the duck embryo the function of the YSM, proventriculus, and small intestine in protein digestion and uptake. We tested the expression of aminopeptidase N (APN) and the oligopeptide transporter PepT1 as well as the expression of cathepsin B (CTSB) and cathepsin D (CTSD) lysosomal genes in the YSM during incubation days 12, 14, 16–18, 20, 22, 24, 26, and 28 (the day of hatch). Also, we examined embryonic duck pepsinogen (EDPg) expression in the proventriculus and APN and PepT1 expression in the small intestine. In the YSM, CTSD expression was weak compared to that of CTSB, and the expression of CTSB, APN, and PepT1 reached its maximum on day 24 and decreased afterwards. In the proventriculus, EDPg expression peaked on days 17 to 20 and decreased thereafter. The APN and PepT1 expression levels were highest in the jejunum and ileum and reached their maximum on day 28. Our results suggest that the YSM plays a role in the degradation and uptake of the peptides that are digested by the activated yolk proteases, and it also functions in the lysosomal digestion of yolk lipoproteins. Furthermore, the proventriculus is possibly involved in the digestion of yolk proteins. Finally, the jejunum and ileum appear to be the primary sites for peptide digestion and absorption at the end of the incubation. Full article

Background: To better understand ischaemia-related molecular alterations, temporal changes in angiogenic Aminopeptidase N (APN/CD13) expression and glucose metabolism were assessed with PET using a rat model of peripheral arterial disease (PAD). Methods: The mechanical occlusion of the base of the left hindlimb triggered using a tourniquet was applied to establish the ischaemia/reperfusion injury model in Fischer-344 rats. 2-[¹⁸F]FDG and [⁶⁸Ga]Ga-NOTA-c(NGR) PET imaging performed 1, 3, 5, 7, and 10 days post-ischaemia induction was followed by Western blotting and immunohistochemical staining for APN/CD13 in ischaemic and control muscle tissue extracts. Results: Due to a cellular adaptation to hypoxia, a gradual increase in [⁶⁸Ga]Ga-NOTA-c(NGR) and 2-[¹⁸F]FDG uptake was observed from post-intervention day 1 to 7 in the ischaemic hindlimbs, which was followed by a drop on day 10. Conforming pronounced angiogenic recovery, the NGR accretion of the ischaemic extremities differed significantly from the controls 5, 7, and 10 days after ischaemia induction (p ≤ 0.05), which correlated with the Western blot and immunohistochemical results. No remarkable radioactivity was depicted between the normally perfused hindlimbs of either the ischaemic or the control groups. Conclusions: The PET-based longitudinal assessment of angiogenesis-associated APN/CD13 expression and glucose metabolism during ischaemia may continue to broaden our knowledge on the pathophysiology of PAD. Full article

Inhibition of insulin-regulated aminopeptidase (IRAP) has been shown to improve cognitive functions in several animal models. Recently, we performed a screening campaign of approximately 10,000 compounds, identifying novel small-molecule-based compounds acting as inhibitors of the enzymatic activity of IRAP. Here we report on the chemical synthesis, structure-activity relationships (SAR) and initial characterization of physicochemical properties of a series of 48 imidazo [1,5-α]pyridine-based inhibitors, including delineation of their mode of action as non-competitive inhibitors with a small L-leucine-based IRAP substrate. The best compound displays an IC₅₀ value of 1.0 µM. We elucidate the importance of two chiral sites in these molecules and find they have little impact on the compound’s metabolic stability or physicochemical properties. The carbonyl group of a central urea moiety was initially believed to mimic substrate binding to a catalytically important Zn²⁺ ion in the active site, although the plausibility of this binding hypothesis is challenged by observation of excellent selectivity versus the closely related aminopeptidase N (APN). Taken together with the non-competitive inhibition pattern, we also consider an alternative model of allosteric binding. Full article

Swine enteric coronaviruses (SECoVs), including porcine deltacoronavirus (PDCoV), transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV), and swine acute diarrhea syndrome coronavirus (SADS-CoV), have caused high mortality in piglets and, therefore, pose serious threats to the pork industry. Coronaviruses exhibit a trend of interspecies transmission, and understanding the host range of SECoVs is crucial for improving our ability to predict and control future epidemics. Here, the replication of PDCoV, TGEV, and PEDV in cells from different host species was compared by measuring viral genomic RNA transcription and protein synthesis. We demonstrated that PDCoV had a higher efficiency in infecting human lung adenocarcinoma cells (A549), Madin–Darby bovine kidney cells (MDBK), Madin–Darby canine kidney cells (MDCK), and chicken embryonic fibroblast cells (DF-1) than PEDV and TGEV. Moreover, trypsin can enhance the infectivity of PDCoV to MDCK cells that are nonsusceptible to TGEV. Additionally, structural analyses of the receptor ectodomain indicate that PDCoV S1 engages Aminopeptidase N (APN) via domain II, which is highly conserved among animal species of different vertebrates. Our findings provide a basis for understanding the interspecies transmission potential of these three porcine coronaviruses. Full article

Since angiogenesis/neoangiogenesis has a major role in tumor development, progression and metastatic spread, the establishment of angiogenesis-targeting imaging and therapeutic vectors is of utmost significance. Aminopeptidase N (APN/CD13) is a pivotal biomarker of angiogenic processes abundantly expressed on the cell surface of active vascular endothelial and various neoplastic cells, constituting a valuable target for cancer diagnostics and therapy. Since the asparagine–glycine–arginine (NGR) sequence has been shown to colocalize with APN/CD13, the research interest in NGR-peptide-mediated vascular targeting is steadily growing. Earlier preclinical experiments have already demonstrated the imaging and therapeutic feasibility of NGR-based probes labeled with different positron emission tomography (PET) and single-photon emission computed tomography (SPECT) radionuclides, including Gallium-68 (⁶⁸Ga), Copper-64 (⁶⁴Cu), Technetium-99m (^99mTc), Lutetium-177 (¹⁷⁷Lu), Rhenium-188 (¹⁸⁸Re) or Bismuth-213 (²¹³Bi). To improve the tumor binding affinity and the retention time of single-receptor targeting peptides, NGR motifs containing heterodimers have been introduced to identify multi-receptor overexpressing malignancies. Preclinical studies with various tumor-bearing experimental animals provide useful tools for the investigation of the in vivo imaging behavior of NGR-based heterobivalent ligands. Herein, we review the reported preclinical achievements on NGR heterodimers that could be highly relevant for the development of further target-specific multivalent compounds in diagnostic and therapeutic settings. Full article

The primary objectives of this study were to assess the inhibitory effects of Allium ampeloprasum L. extract (AAE) and its derived organosulfur and polyphenolic compounds on the enzymatic activities of cGMP-specific PDE V (PDE5) and aminopeptidase N (APN). Additionally, the study aimed to investigate their potential as inhibitors against these two target enzymes through kinetic analyses and molecular docking studies. The in vitro enzyme assays demonstrated that both AAE and its derived compounds significantly decreased the activity of PDE5 and APN. Further analyses involving kinetics and molecular docking provided insights into the specific inhibitor types of AAE and its derived compounds along with the proposed molecular docking models illustrating the interactions between the ligands (the compounds) and the enzymes (PDE5 and APN). In particular, AAE-derived polyphenolic compounds showed relatively stable binding affinity (−7.2 to −8.3 kcal/mol) on PDE5 and APN. Our findings proved the potential as an inhibitor against PDE5 and APN of AAE and AAE-derived organosulfur and polyphenolic compounds as well as a functional material for erectile dysfunction improvement. Full article

Angiogenesis plays a crucial role in tumour progression and metastatic spread; therefore, the development of specific vectors targeting angiogenesis has attracted the attention of several researchers. Since angiogenesis-associated aminopeptidase N (APN/CD13) is highly expressed on the surface of activated endothelial cells of new blood vessels and a wide range of tumour cells, it holds great promise for imaging and therapy in the field of cancer medicine. The selective binding capability of asparagine-glycine-arginine (NGR) motif containing molecules to APN/CD13 makes radiolabelled NGR peptides promising radiopharmaceuticals for the non-invasive, real-time imaging of APN/CD13 overexpressing malignancies at the molecular level. Preclinical small animal model systems are major keystones for the evaluation of the in vivo imaging behaviour of radiolabelled NGR derivatives. Based on existing literature data, several positron emission tomography (PET) and single-photon emission computed tomography (SPECT) radioisotopes have been applied so far for the labelling of tumour vasculature homing NGR sequences such as Gallium-68 (⁶⁸Ga), Copper-64 (⁶⁴Cu), Technetium-99m (^99mTc), Lutetium-177 (¹⁷⁷Lu), Rhenium-188 (¹⁸⁸Re), or Bismuth-213 (²¹³Bi). Herein, a comprehensive overview is provided of the recent preclinical experiences with radiolabelled imaging probes targeting angiogenesis. Full article

Angiogenesis-related cell-surface molecules, including integrins, aminopeptidase N, vascular endothelial growth factor, and gastrin-releasing peptide receptor (GRPR), play a crucial role in tumour formation. Radiolabelled imaging probes targeting angiogenic biomarkers serve as valuable vectors in tumour identification. Nowadays, there is a growing interest in novel radionuclides other than gallium-68 (⁶⁸Ga) or copper-64 (⁶⁴Cu) to establish selective radiotracers for the imaging of tumour-associated neo-angiogenesis. Given its ideal decay characteristics (E_β⁺_average: 632 KeV) and a half-life (T_1/2 = 3.97 h) that is well matched to the pharmacokinetic profile of small molecules targeting angiogenesis, scandium-44 (⁴⁴Sc) has gained meaningful attention as a promising radiometal for positron emission tomography (PET) imaging. More recently, intensive research has been centered around the investigation of ⁴⁴Sc-labelled angiogenesis-directed radiopharmaceuticals. Previous studies dealt with the evaluation of ⁴⁴Sc-appended a_vb₃ integrin–affine Arg-Gly-Asp (RGD) tripeptides, GRPR-selective aminobenzoyl–bombesin analogue (AMBA), and hypoxia-associated nitroimidazole derivatives in the identification of various cancers using experimental tumour models. Given the tumour-related hypoxia- and angiogenesis-targeting capability of these PET probes, ⁴⁴Sc seems to be a strong competitor of the currently used positron emitters in radiotracer development. In this review, we summarize the preliminary preclinical achievements with ⁴⁴Sc-labelled angiogenesis-specific molecular probes. Full article

It is known that the spike protein of human coronaviruses can bind to a secondary receptor, or coreceptor, to facilitate the virus entry. While HCoV-229E uses human aminopeptidase N (hAPN) as a receptor, HCoV-OC43 binds to 9-O-acetyl-sialic acid (9-O-Ac-Sia), which is linked in a terminal way to the oligosaccharides that decorate glycoproteins and gangliosides on the surface of the host cell. Thus, evaluating the possible inhibitory activity of heparan sulfate, a linear polysaccharide found in animal tissues, and enoxaparin sodium on these viral strains can be considered attractive. Therefore, our study also aims to evaluate these molecules’ antiviral activity as possible adsorption inhibitors against non-SARS-CoV. Once the molecules’ activity was verified in in vitro experiments, the binding was studied by molecular docking and molecular dynamic simulations confirming the interactions at the interface of the spike proteins. Full article

Porcine epidemic diarrhea (PED) is an acute and severe atrophic enteritis caused by porcine epidemic diarrhea virus (PEDV) that infects pigs and makes huge economic losses to the global swine industry. Previously, researchers have believed that porcine aminopeptidase-N (pAPN) was the primary receptor for PEDV, but it has been found that PEDV can infect pAPN knockout pigs. Currently, the functional receptor for PEDV remains unspecified. In the present study, we performed virus overlay protein binding assay (VOPBA), found that ATP1A1 was the highest scoring protein in the mass spectrometry results, and confirmed that the CT structural domain of ATP1A1 interacts with PEDV S1. First, we investigated the effect of ATP1A1 on PEDV replication. Inhibition of hosts ATP1A1 protein expression using small interfering RNA (siRNAs) significantly reduced the cells susceptibility to PEDV. The ATP1A1-specific inhibitors Ouabain (a cardiac steroid) and PST2238 (a digitalis toxin derivative), which specifically bind ATP1A1, could block the ATP1A1 protein internalization and degradation, and consequently reduce the infection rate of host cells by PEDV significantly. Additionally, as expected, overexpression of ATP1A1 notably enhanced PEDV infection. Next, we observed that PEDV infection of target cells resulted in upregulation of ATP1A1 at the mRNA and protein levels. Furthermore, we found that the host protein ATP1A1 was involved in PEDV attachment and co-localized with PEDV S1 protein in the early stage of infection. In addition, pretreatment of IPEC-J2 and Vero-E6 cells with ATP1A1 mAb significantly reduced PEDV attachment. Our observations provided a perspective on identifying key factors in PEDV infection, and may provide valuable targets for PEDV infection, PEDV functional receptor, related pathogenesis, and the development of new antiviral drugs. Full article

Since NGR-tripeptides (asparagine-glycine-arginine) selectively target neoangiogenesis-associated Aminopeptidase N (APN/CD13) on cancer cells, we aimed to evaluate the in vivo tumour targeting capability of radiolabelled, NGR-containing, ANP/CD13-selective [²¹³Bi]Bi-DOTAGA-cKNGRE in CD13pos. HT1080 fibrosarcoma-bearing severe combined immunodeficient CB17 mice. 10 ± 1 days after cancer cell inoculation, positron emission tomography (PET) was performed applying [⁶⁸Ga]Ga-DOTAGA-cKNGRE for tumour verification. On the 7th, 8th, 10th and 12th days the treated group of tumourous mice were intraperitoneally administered with 4.68 ± 0.10 MBq [²¹³Bi]Bi-DOTAGA-cKNGRE, while the untreated tumour-bearing animals received 150 μL saline solution. In addition to body weight (BW) and tumour volume measurements, ex vivo biodistribution studies were conducted 30 and 90 min postinjection (pi.). The following quantitative standardised uptake values (SUV) confirmed the detectability of the HT1080 tumours: SUV_mean and SUV_max: 0.37 ± 0.09 and 0.86 ± 0.14, respectively. Although no significant difference (p ≤ 0.05) was encountered between the BW of the treated and untreated mice, their tumour volumes measured on the 9th, 10th and 12th days differed significantly (p ≤ 0.01). Relatively higher [²¹³Bi]Bi-DOTAGA-cKNGRE accumulation of the HT1080 neoplasms (%ID/g: 0.80 ± 0.16) compared with the other organs at 90 min time point yields better tumour-to-background ratios. Therefore, the therapeutic application of APN/CD13-affine [²¹³Bi]Bi-DOTAGA- cKNGRE seems to be promising in receptor-positive fibrosarcoma treatment. Full article