Detection of cellular hypoxia by pimonidazole adduct immunohistochemistry in kidney disease: methodological pitfalls and their solution.

Pimonidazole adduct immunohistochemistry is one of the few available methods for assessing renal tissue hypoxia at the cellular level. It appears to be prone to artifactual false positive staining under some circumstances. Here, we assessed the nature of this false positive staining and, having determined how to avoid it, reexamined the nature of cellular hypoxia in rat models of kidney disease. When a mouse-derived anti-pimonidazole primary antibody was used, two types of staining were observed. First, there was diffuse staining of the cytoplasm of tubular epithelial cells, which was largely absent when the primary antibody was omitted from the incubation protocol or in tissues known not to contain pimonidazole adducts. Second, there was staining of the apical membranes of tubular epithelial cells, debris within the lumen of renal tubules, including tubular casts, and the interstitium; this latter staining was present even when the primary antibody was omitted from the incubation protocol. Such false positive staining was particularly prominent in acutely injured kidneys. It could not be avoided by preincubation of sections with a mouse IgG blocking reagent. Furthermore, preadsorption of the secondary antibody against rat Ig abolished all staining; however, when a rabbit-derived polyclonal anti-pimonidazole primary antibody was used, the false positive staining was largely avoided. Using this method, we confirmed the presence of hypoxia, localized mainly to the tubular epithelium, in the acute phase of severe renal ischemia-reperfusion injury, adenine-induced chronic kidney disease, and polycystic kidney disease. We conclude that this new method provides improved detection of renal cellular hypoxia.

Evaluation of cytokine profile and HLA association in benznidazole related cutaneous reactions in patients with Chagas disease.

BACKGROUND: Benznidazole is the drug of choice for Chagas disease. The major drawback of this drug is the high adverse events rate, being cutaneous reactions the most frequent one, leading to definitive withdrawal of treatment in 15%-30% of patients. METHODS: Prospective observational study where adult Chagas disease patients accepting to receive benznidazole (100 mg/8 hours for 60 days) were included. The objective was to characterize the skin toxicity of benznidazole in patients with Chagas disease, determine the serum cytokine profile, and evaluate the potential association with specific HLA alleles and benznidazole concentration. Serum cytokine levels were measured at day 0, 15, and 60 of treatment. Class I and II HLA alleles were determined. When cutaneous reaction was detected, a skin biopsy was performed. Serum benznidazole concentration was determined at the time of cutaneous reaction, or at day 15 of treatment. RESULTS: Fifty-two patients were included, 20(38.5%) had cutaneous reaction, and median time of appearance was 9 days. Skin biopsies showed histopathological findings consistent with drug eruption. Patients with cutaneous drug-reaction had higher proportion of eosinophilia during treatment, and higher interleukin (IL)-5 and IL-10 serum concentrations at day 15 of treatment than those without cutaneous reaction. Treatment interruption (that included moderate-severe cutaneous reactions) was more frequent in patients carrying HLA-B*3505 allele (45.5% vs 15.4%, P = .033). No differences in benznidazole serum concentration were found. CONCLUSIONS: Benznidazole related cutaneous reaction rate is high, and it was produced by a delayed hypersensitivity reaction with a Th2 response. Carrying HLA-B*3505 allele could be associated with moderate-severe cutaneous reaction.

In Vivo Hypoxia PET Imaging Quantifies the Severity of Arthritic Joint Inflammation in Line with Overexpression of Hypoxia-Inducible Factor and Enhanced Reactive Oxygen Species Generation.

Hypoxia is essential for the development of autoimmune diseases such as rheumatoid arthritis (RA) and is associated with the expression of reactive oxygen species (ROS), because of the enhanced infiltration of immune cells. The aim of this study was to demonstrate the feasibility of measuring hypoxia noninvasively in vivo in arthritic ankles with PET/MRI using the hypoxia tracers 18F-fluoromisonidazole (18F-FMISO) and 18F-fluoroazomycinarabinoside (18F-FAZA). Additionally, we quantified the temporal dynamics of hypoxia and ROS stress using L-012, an ROS-sensitive chemiluminescence optical imaging probe, and analyzed the expression of hypoxia-inducible factors (HIFs). Methods: Mice underwent noninvasive in vivo PET/MRI to measure hypoxia or optical imaging to analyze ROS expression. Additionally, we performed ex vivo pimonidazole-/HIF-1α immunohistochemistry and HIF-1α/2α Western blot/messenger RNA analysis of inflamed and healthy ankles to confirm our in vivo results. Results: Mice diseased from experimental RA exhibited a 3-fold enhancement in hypoxia tracer uptake, even in the early disease stages, and a 45-fold elevation in ROS expression in inflamed ankles compared with the ankles of healthy controls. We further found strong correlations of our noninvasive in vivo hypoxia PET data with pimonidazole and expression of HIF-1α in arthritic ankles. The strongest hypoxia tracer uptake was observed as soon as day 3, whereas the most pronounced ROS stress was evident on day 6 after the onset of experimental RA, indicating that tissue hypoxia can precede ROS stress in RA. Conclusion: Collectively, for the first time to our knowledge, we have demonstrated that the noninvasive measurement of hypoxia in inflammation using 18F-FAZA and 18F-FMISO PET imaging represents a promising new tool for uncovering and monitoring rheumatic inflammation in vivo. Further, because hypoxic inflamed tissues are associated with the overexpression of HIFs, specific inhibition of HIFs might represent a new powerful treatment strategy.

An immunohistochemical assessment of hypoxia in prostate carcinoma using pimonidazole: implications for radioresistance.

PURPOSE: To investigate the presence of hypoxia in human prostate carcinoma by using pimonidazole immunohistochemical labeling in radical prostatectomy specimens. METHODS AND MATERIALS: Forty-three patients (median age, 69 years; range, 49-83 years) with localized prostate adenocarcinoma received 0.5 gm/m2 i.v. pimonidazole 16-24 h before radical prostatectomy. Hypoxia was detected with a monoclonal antibody directed against pimonidazole and scored in formalin-fixed, paraffin-embedded sections. Median and maximal vessel counts were measured with CD34. RESULTS: Thirty-seven patients completed the study. Pimonidazole binding was present in prostate carcinomas in 34 of 37 patients (92%) and in benign prostatic hyperplasia in 35 of 37 patients (95%). A positive correlation of 3+ pimonidazole binding with Gleason score was demonstrated (Spearman's rank, p = 0.044). Vascularity scores did not correlate with hypoxic status or clinical prognostic parameters. CONCLUSION: Prostate carcinoma and benign prostatic hyperplasia have significant areas of hypoxia; greater hypoxia scores are seen with more aggressive prostate cancer. It is postulated that a hypoxic microenvironment within the prostate might be responsible for the promotion of secondary genetic alterations and angiogenic stimulation, leading to malignant progression, a more aggressive cell phenotype, and greater radioresistance. Modification of radiation regimens to specifically target hypoxia might improve local tumor control.

Detection of hypoxic cells by monoclonal antibody recognizing 2-nitroimidazole adducts.

Hypoxic cells in tissue pose many medical problems, and there is a need for more accurate measurements of tissue hypoxia. However, measurement of the pO2 and the extent of hypoxia within normal and tumor tissue have proven difficult. One of the most sensitive of the currently available methodologies involves the oxygen-dependent metabolic activation of nitroheterocyclic drugs, leading to adducts between the drugs and cellular macromolecules. Limitations of the present drugs and adduct-detection methods prompted the present studies. A pentafluorinated derivative [EF5; 2-(2-nitro-1H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl)acetam ide] of etanidazole was synthesized with the expectation of lessening some of the non-oxygen-dependent variability in adduct formation observed previously with other nitroaromatic compounds. EF5-protein conjugates, prepared by radiochemical reduction, were found to be immunogenic and allowed the development of monoclonal antibodies. One of these antibodies, ELK2-4, has been characterized and found to be highly specific for the EF5 adducts whether produced radiochemically or by cellular bioreductive metabolism. 9L rat glioma cells pretreated with EF5 under hypoxic, compared with aerobic, conditions were readily discriminated immunochemically using fluorochrome-conjugated secondary antibodies which recognize the ELK2-4 antibody subtype (IgG1). Similarly, the central region of multicenter spheroids, composed of EMT6 mouse mammary sarcoma cells, was selectively visualized by immunohistochemistry after the spheroids were incubated for 4 h in 0.5 mM EF5. Tumor biopsy, preparation, and immunohistochemical staining 24 h after treatment of tumor-bearing animals with drug also demonstrated high contrast regions within EMT6 mouse or Morris 7777 hepatoma rat tumors. The use of this new compound and its highly specific monoclonal antibody may allow elucidation of bioreductive metabolism of the nitroheterocyclics and significantly improve technologies for the quantitation of tissue pO2.

Inhibition of delayed hypersensitivity by metronidazole and misonidazole.

The effect on cell-mediated immunity of two hypoxic cell radiosensitizers, metronidazole and misonidazole, was examined. Immunocompetence was assayed by measuring delayed hypersensitivity reactions in mice sensitized on the abdomen with 2,4-dinitro-1-fluorobenzene (DNFB) and subsequently challenged on the ears with DNFB. Single and fractionated treatments with misonidazole or metronidazole were found to suppress delayed hypersensitivity reactions to DNFB. This finding is in agreement with other data in the literature which show that many imidazoles, including nitroimidazoles, inhibit aspects of the cell-mediated immune response in animals and man. The potential immunosuppressive effects of nitroheterocyclic radiosensitizers should be considered when these agents are evaluated in the laboratory or used in the clinic.

Improved immunohistochemical method for detecting hypoxia gradients in mouse tissues and tumors.

We describe an improved immunohistochemical procedure for detecting regions of hypoxia in normal organs and tumors in mice. The method employs a primary fluorescein-conjugated mouse monoclonal antibody directed against pimonidazole protein adducts that are created in hypoxic tissues and a secondary mouse anti-fluorescein antibody that is conjugated to horseradish peroxidase. Using these reagents, we clearly visualized the regions of relative hypoxia in implanted tumors in mice as well as in normal organs such as liver and kidney. Significantly, the resulting tissue sections were remarkably free of the background staining that is characteristically observed when rodent antibodies are used to detect antigens in rodent tissues.

Hypoxia markers are expressed in interneurons exposed to recurrent seizures.

An early but transient decrease in oxygen availability occurs during experimentally induced seizures. Using pimonidazole, which probes hypoxic insults, we found that by increasing the duration of pilocarpine-induced status epilepticus (SE) from 30 to 120 min, counts of pimonidazole-immunoreactive neurons also increased (P < 0.01, 120 vs 60 and 30 min). All the animals exposed to SE were immunopositive to pimonidazole, but a different scenario emerged during epileptogenesis when a decrease in pimonidazole-immunostained cells occurred from 7 to 14 days, so that only 1 out of 4 rats presented with pimonidazole-immunopositive cells. Pimonidazole-immunoreactive cells robustly reappeared at 21 days post-SE induction when all animals (7 out of 7) had developed spontaneous recurrent seizures. Specific neuronal markers revealed that immunopositivity to pimonidazole was present in cells identified by neuropeptide Y (NPY) or somatostatin antibodies. At variance, neurons immunopositive to parvalbumin or cholecystokinin were not immunopositive to pimonidazole. Pimonidazole-immunopositive neurons expressed remarkable immunoreactivity to hypoxia-inducible factor 1α (HIF-1α). Interestingly, surgical samples obtained from pharmacoresistant patients showed neurons co-labeled by HIF-1α and NPY antibodies. These interneurons, along with parvalbumin-positive interneurons that were negative to HIF-1α, showed immunopositivity to markers of cell damage, such as high-mobility group box 1 in the cytoplasm and cleaved caspase-3 in the nucleus. These findings suggest that interneurons are continuously endangered in rodent and human epileptogenic tissue. The presence of hypoxia and cell damage markers in NPY interneurons of rats and patients presenting with recurrent seizures indicates a mechanism of selective vulnerability in a specific neuronal subpopulation.

Symptomatic Trichomonas vaginalis infection in the setting of severe nitroimidazole allergy: successful treatment with boric acid.

This report describes a patient with symptomatic Trichomonas vaginalis infection who was unable to tolerate nitroimidazole drugs because of severe hypersensitivity, for which desensitisation was not possible. Use of intravaginal clotrimazole, intravaginal paromomycin, intravaginal furazolidone, povidone-iodine douches, and oral nitazoxanide were unsuccessful in eradicating the patient's T. vaginalis infection. A 2-month course of intravaginal topical boric acid subsequently achieved a complete symptomatic cure and the patient remained T. vaginalis wet prep- and culture-negative 60 days after treatment.

Improved screening method for the detection of a range of nitroimidazoles in various matrices by optical biosensor.

An immunobiosensor assay was developed for the multi-residue screening of a range of nitroimidazole compounds in various species and sample types including porcine, bovine and ovine kidney, avian liver, serum and eggs and bovine milk. A polyclonal antibody which binds at least seven of the major nitroimidazoles and their metabolites was raised in a sheep after inoculation with a metronidazole protein conjugate. Sample homogenates were extracted into acetonitrile and subjected to micro-centrifugation prior to biosensor analysis. Validation data obtained from the analysis of 20 fortified samples has shown that the method has a detection capability (CCbeta) of less than 1 microgkg(-1) (or microgL(-1)) for dimetridazole (DMZ) in all species and matrices investigated. In addition, cross-reactivity data and the analysis of a small number of fortified samples have shown that the method will also detect a range of other major parent nitroimidazoles and their metabolites including ronidazole (RNZ), ipronidazole (IPZ), metronidazole (MNZ), hydroxymetronidazole (MNZOH), hydroxydimetridazole (DMZOH) and hydroxyipronidazole (IPZOH). The cross-reactivity profile and validation data for the detection of these nitroimidazoles are presented together with the results obtained following the analysis of a small number of incurred samples using the developed method.

Radio-copper-labeled Cu-ATSM: an indicator of quiescent but clonogenic cells under mild hypoxia in a Lewis lung carcinoma model.

UNLABELLED: The purpose of this study is to reveal characteristics of (64)Cu-labeled diacetyl-bis(N(4)-methylthiosemicarbazone) ([(64)Cu]Cu-ATSM) during cell proliferation and hypoxia by autoradiography imaging and immunohistochemical staining. METHODS: The intratumoral distributions of [(64)Cu]Cu-ATSM and [(18)F]-2-fluoro-2-deoxy-D-glucose ([(18)F]FDG) in mice implanted with Lewis lung carcinoma (LLC1) tumor cells according to dual autoradiography were compared with the immunohistochemical staining patterns of proliferating markers [Ki-67 and 5-bromo-2'-deoxyuridine (BrdU)] and a hypoxic marker (pimonidazole). A clonogenic assay was performed using the cells of LLC1 tumor-implanted mice, and it was compared with the distribution of [(64)Cu]Cu-ATSM. RESULTS: [(64)Cu]Cu-ATSM mainly accumulated at the edge of tumors, whereas [(18)F]FDG was distributed inside the tumor and inside the [(64)Cu]Cu-ATSM accumulation. The number of Ki-67-positive cells/area tended to increase with [(18)F]FDG accumulation and decrease with [(64)Cu]Cu-ATSM accumulation. On the other hand, the number of BrdU-positive cells/area was negatively correlated with [(18)F]FDG accumulation and positively correlated with [(64)Cu]Cu-ATSM accumulation. High [(64)Cu]Cu-ATSM accumulation was found outside the high-[(18)F]FDG-accumulation and pimonidazole-positive regions. Colony formation ability was significantly higher in the tumor cells obtained from high-[(64)Cu]Cu-ATSM-accumulation regions than the cells from the intermediate- and the low-accumulation regions. CONCLUSION: [(64)Cu]Cu-ATSM accumulation regions in tumor cells indicate quiescent but clonogenic tumor cells under mild hypoxia. [(64)Cu]Cu-ATSM could play an important role in planning appropriate tumor radiotherapy.

Evaluation of hypoxia in an experimental rat tumour model by [(18)F]fluoromisonidazole PET and immunohistochemistry.

This study aimed to evaluate tumour hypoxia by comparing [(18)F]Fluoromisonidazole uptake measured using positron emission tomography ([(18)F]FMISO-PET) with immunohistochemical (IHC) staining techniques. Syngeneic rhabdomyosarcoma (R1) tumour pieces were transplanted subcutaneously in the flanks of WAG/Rij rats. Tumours were analysed at volumes between 0.9 and 7.3 cm(3). Hypoxic volumes were defined using a 3D region of interest on 2 h postinjection [(18)F]FMISO-PET images, applying different thresholds (1.2-3.0). Monoclonal antibodies to pimonidazole (PIMO) and carbonic anhydrase IX (CA IX), exogenous and endogenous markers of hypoxia, respectively, were used for IHC staining. Marker-positive fractions were microscopically measured for each tumour, and hypoxic volumes were calculated. A heterogeneous distribution of hypoxia was observed both with histology and [(18)F]FMISO autoradiography. A statistically significant correlation (P<0.05) was obtained between the hypoxic volumes defined with [(18)F]FMISO-PET and the volumes derived from the PIMO-stained tumour sections (r=0.9066; P=0.0001), regardless of the selected threshold between 1.4 and 2.2. A similar observation was made with the CA IX staining (r=0.8636; P=0.0006). The relationship found between [(18)F]FMISO-PET and PIMO- and additionally CA IX-derived hypoxic volumes in rat rhabdomyosarcomas indicates the value of the noninvasive imaging method to measure hypoxia in whole tumours.

Chronic intragastric alcohol exposure causes hypoxia and oxidative stress in the rat pancreas.

The effect of chronic enteral ethanol on pancreatic hypoxia was investigated using the hypoxia marker, pimonidazole. Male Wistar rats were fed an ethanol-containing diet for 3 weeks using an enteral model shown to cause pancreatic damage; pimonidazole (120 mg/kg i.v.) was injected 1h before sacrifice. Pimonidazole and 4-hydroxynonenal (an index of lipid peroxidation) adducts were detected immunochemically. Breathing air with low oxygen content (8% O(2)) for 1h increased pimonidazole adduct accumulation approximately 2-fold in pancreata of nai;ve rats, confirming that this technique will detect increases in hypoxia in pancreata. Pancreata of rats fed ethanol began to show signs of damage after 3 weeks. Ethanol feeding also significantly increased pimonidazole adducts in pancreas approximately 2-fold (1 or 3 weeks of ethanol produced similar values). Concomitant with increasing hypoxia in the pancreas, alcohol also caused a significant increase in 4-hydroxynonenal adducts, indicative of increased oxidative stress. These results indicate that chronic ethanol causes hypoxia at the cellular level in the pancreas in vivo; further, the data support the hypothesis that hypoxia is involved in mechanisms of chronic alcoholic pancreatitis.

Determination of hypoxic region by hypoxia marker in developing mouse embryos in vivo: a possible signal for vessel development.

Hypoxia is a well-known signal for angiogenesis, but the recent proposal that hypoxia exists in developing embryonic tissues and that it induces vascular development remains to be proven. In the present study, we demonstrate the presence of hypoxia in normal developing embryos by means of a hypoxia marker, pimonidazole, and its associated antibody. Our data clearly show that hypoxia marker immunoreactivity was highly detected in developing neural tubes, heart, and intersomitic mesenchyme at an early stage of organogenesis, suggesting that hypoxia may exist in the early stages of embryo development. We also found that hypoxia inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) were spatiotemporally co-localized with possible hypoxic regions in embryos. Investigation of platelet endothelial cell adhesion molecule (PECAM) expression provides evidence that endothelial cells proliferate and form the vessels in the hypoxic region in developing organs. Furthermore, we found that hypoxia induced both HIF-1alpha and VEGF in F9 embryonic stem and differentiated cells. Thus, we suggest that hypoxia may exist widely in developing embryonic tissues and that it may act as a signal for embryonic blood vessel formation in vivo.