Detection of apoptotic cell death in the thymus of dexamethasone treated rats using [123I]annexin V and in situ oligonucleotide ligation

The effect of traumatic exposure on thymus weight level after dexamethasone application in rats

Introduction: Thymus is the central lymphoid organ responsible for proper immune cell maturation, hence ensuring functional T cell repertoire. Stress induces elevated levels of hormones that profoundly alter immune response. Susceptibility to physiologically synthesised and exogenously applied glucocorticoids make thymus an ideal substrate for anatomical and morphological analysis. Aim: Our research aimed to investigate the impact of endogenous and exogenous glucocorticoids on thymus weight level. Material and methods: Experimental procedure was conducted on male Wistar rats, 12 in total, divided into 2 groups - control and experimental. Latter was exposed to two kinds of stressors. Acute stress included immobilization with exposure to the predator's odor. Chronic social stress included rotation of the animals held in pairs. On the 11th day of the experimental procedure, half of the experimental group received dexamethasone treatment (impact of endogenous + exogenous glucocorticoids) while the other half did not (impact of endogenous glucocorticoids). After the experiment, animals were sacrificed and their thymuses were obtained and measured. For statistical analysis, ANOVA was used to test differences between groups and LSD test for each group testing. Results: Results showed statistically significant differences between the thymus mass of different groups (F=4.336, p=0.048). The part of the experimental group that received dexamethasone had a smaller thymus weight level compared to the part of the experimental group that received no treatment (p=0.024). No statistically relevant results were obtained after comparing thymus masses from impact of endogenous glucocorticoids and control group (p>0.05). Conclusion: Exogenous glucocorticoids induce morphological changes in thymus which are observed in decreased weight level. Stress induced thymus apoptosis, but it was not sufficient to lead to decrease in thymic mass. Our further experiments will put emphasis on understanding of morphological and anatomical changes caused by stress.

Hypotensive Activity of Ethanolic Extracts of Morinda citrifolia L. Leaves and Fruit in Dexamethasone-Induced Hypertensive Rat

The effect of ethanolic extract of Morinda citrifolia leaves and fruit on blood pressure in dexamethasone-induced hypertension rat was evaluated. Total phenolic content of Morinda citrifolia leaves ethanolic extract (MCLEE) and Morinda citrifolia leaves ethanolic extract (MCFEE) was 1.789 ± 0.116 and 1.677 ± 0.051 mg of gallic acid equivalents per gram sample, respectively. Rutin level in MCLEE was 0.92 ± 0.19%, and scopoletin level in MCFEE was 0.46 ± 0.05%. MCLEE, MCFEE, and its extract combination significantly decreased the blood pressure of hypertensive rats. The combination group showed highest hypotensive activity by lowering systolic blood pressure by 16.71 ± 3.95%, diastolic blood pressure by 21.49 ± 7.90%, and mean arterial blood pressure by 19.58% ± 6.35. All extract treatments have not been able to repair or inhibit renal damage caused by dexamethasone induction.

The effect of alpha-lipoic acid on mitochondrial superoxide and glucocorticoid-induced hypertension

Aims. To examine the effect of alpha-lipoic acid, an antioxidant with mitochondrial superoxide inhibitory properties, on adrenocorticotrophic hormone- (ACTH-HT) and dexamethasone-induced hypertensions (DEX-HT) in rats and if any antihypertensive effect is mediated via mitochondrial superoxide inhibition. Methods. In a prevention study, rats received ground food or alpha-lipoic-acid-laced food (10 mg/rat/day) for 15 nights. Saline, adrenocorticotrophic hormone (ACTH, 0.2 mg/kg/day), or dexamethasone (DEX, 10 μg/rat/day) was injected subcutaneously from day 5 to day 11. In a reversal study, rats received alpha-lipoic-acid-laced food 4 days after commencement of saline or DEX. Tail-cuff systolic blood pressure (SBP) was measured second daily. Kidney mitochondrial superoxide was examined using (MitoSOX) Red (MitoSOX) via flow cytometry. Results. SBP was increased by ACTH (P < 0.0005) and DEX (P < 0.0005). Alpha-lipoic acid alone did not alter SBP. With alpha-lipoic acid pretreatment, SBP was increased by ACTH (P′ < 0.005) but not by DEX. Alpha-lipoic partially prevented ACTH-HT (P′ < 0.0005) and fully prevented DEX-HT (P′ < 0.0005) but failed to reverse DEX-HT. ACTH and DEX did not increase MitoSOX signal. In ACTH-hypertensive rats, high-dose alpha-lipoic acid (100 mg/rat/day) did not decrease SBP further but raised MitoSOX signal (P < 0.001), suggesting prooxidant activity. Conclusion. Glucocorticoid-induced hypertension in rats is prevented by alpha-lipoic acid via mechanisms other than mitochondrial superoxide reduction.

In vivo targeting of cell death using a synthetic fluorescent molecular probe

A synthetic, near-infrared, fluorescent probe, named PSS-794 was assessed for its ability to detect cell death in two animal models. The molecular probe contains a zinc(II)-dipicolylamine (Zn(2+)-DPA) affinity ligand that selectively targets exposed phosphatidylserine on the surface of dead and dying cells. The first animal model used rats that were treated with dexamethasone to induce thymic atrophy. Ex vivo fluorescence imaging and histological analysis of excised organs showed thymus uptake of PSS-794 was four times higher than a control fluorophore that lacked the Zn(2+)-DPA affinity ligand. In addition, the presence of PSS-794 produced a delayed and higher build up of dead and dying cells in the rat thymus. The second animal model employed focal beam radiation to induce cell death in tumor-bearing rats. Whole-body and ex vivo imaging showed that the amount of PSS-794 in a radiation-treated tumor was almost twice that in a non-treated tumor. The results indicate that PSS-794 may be useful for preclinical optical detection of tumor cell death due to therapy.

In vivo imaging of apoptosis in oncology: an update

In this review, data on noninvasive imaging of apoptosis in oncology are reviewed. Imaging data available are presented in order of occurrence in time of enzymatic and morphologic events occurring during apoptosis. Available studies suggest that various radiopharmaceutical probes bear great potential for apoptosis imaging by means of positron emission tomography and single-photon emission computed tomography (SPECT). However, for several of these probes, thorough toxicologic studies are required before they can be applied in clinical studies. Both preclinical and clinical studies support the notion that 99mTc-hydrazinonicotinamide-annexin A5 and SPECT allow for noninvasive, repetitive, quantitative apoptosis imaging and for assessing tumor response as early as 24 hours following treatment instigation. Bioluminescence imaging and near-infrared fluorescence imaging have shown great potential in small-animal imaging, but their usefulness for in vivo imaging in humans is limited to structures superficially located in the human body. Although preclinical tumor-based data using high-frequency-ultrasonography (US) are promising, whether or not US will become a routinely clinically useful tool in the assessment of therapy response in oncology remains to be proven. The potential of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) for imaging late apoptotic processes is currently unclear. Neither 31P MRS nor 1H MRS signals seems to be a unique identifier for apoptosis. Although MRI-measured apparent diffusion coefficients are altered in response to therapies that induce apoptosis, they are also altered by nonapoptotic cell death, including necrosis and mitotic catastrophe. In the future, rapid progress in the field of apoptosis imaging in oncology is expected.

In situ ligation: a decade and a half of experience

The in situ ligation (ISL) methodology detects apoptotic cells by the presence of characteristic DNA double-strand breaks. A labeled double-stranded probe is ligated to the double-strand breaks in situ on tissue sections. Like the popular TUNEL assay, ISL detects cells in apoptosis based on the ongoing destruction of DNA by apoptotic nucleases. In comparison to TUNEL, it is more specific for apoptosis versus other causes of DNA damage, both repairable damage and necrosis. In the decade and a half since its introduction, ISL has been used in several hundred publications. Here we review the development of the method, its current status, and its uses and limitations.

Activity-based probes: discovering new biology and new drug targets

The development and application of chemical technologies enabling direct analysis of enzyme activity in living systems has undergone explosive growth in recent years. Activity-based protein profiling (ABPP) is a key constituent of this broad field, and is among the most powerful and mature chemical proteomic technologies. This tutorial review introduces the essential features of ABPP and the design and application of activity-based probes (ABPs) from drug target elucidation and in vivo visualisation of enzyme activity to comprehensive profiling of the catalytic content of living systems, and the discovery of new biological pathways.

Noninvasive optical imaging of apoptosis by caspase-targeted activity-based probes

Imaging agents that enable direct visualization and quantification of apoptosis in vivo have great potential value for monitoring chemotherapeutic response as well as for early diagnosis and disease monitoring. We describe here the development of fluorescently labeled activity-based probes (ABPs) that covalently label active caspases in vivo. We used these probes to monitor apoptosis in the thymi of mice treated with dexamethasone as well as in tumor-bearing mice treated with the apoptosis-inducing monoclonal antibody Apomab (Genentech). Caspase ABPs provided direct readouts of the kinetics of apoptosis in live mice, whole organs and tissue extracts. The probes produced a maximum fluorescent signal that could be monitored noninvasively and that coincided with the peak in caspase activity, as measured by gel analysis. Overall, these studies demonstrate that caspase-specific ABPs have the potential to be used for noninvasive imaging of apoptosis in both preclinical and clinical settings.

The magnitude and temporal dependence of apoptosis early after myocardial ischemia with or without reperfusion

In view of the conventional wisdom in the cardiology literature that apoptosis is extensive early after myocardial ischemia, predicated largely from results with the TUNEL assay known to be nonspecific, this study was performed to delineate its extent with multiple assays and at multiple intervals. Coronary occlusion with and without subsequent revascularization was induced in 10-wk-old C57BL6 mice subjected to 1 or 4 h of transient ligation followed by 24 h of reperfusion, or 24 h persistent ligation. Apoptosis was quantified throughout the left ventricle immunohistochemically by assay of TUNEL, single-stranded DNA (ssDNA), and cleaved caspase 3; electron microscopy (EM); and activity assays of caspase 3 and 8. TUNEL staining was marked, but ssDNA and cleaved caspase 3 staining were significantly less (P<0.001 compared with TUNEL), and apoptosis defined by EM was virtually absent in all groups. Caspase 3 and caspase 8 activities per milligram protein were not significantly different from those in normal hearts. Only rare, potentially apoptotic cells were seen by EM in hearts from any group. Thus, the results with TUNEL were not specific, and the extent of apoptosis was markedly less than that predicated on the results with the TUNEL procedure. Apoptosis is de minimus early after transitory or persistent ischemia, though it is overestimated by TUNEL assays. Thus, antiapoptotic interventions per se are not likely to preserve substantial amounts of myocardium early after ischemic insults.

Bone marrow sinusoidal endothelial cells undergo nonapoptotic cell death and are replaced by proliferating sinusoidal cells in situ to maintain the vascular niche following lethal irradiation

OBJECTIVE

Bone marrow sinusoids remain predominantly host-derived following bone marrow transplantation. Systematic analysis was conducted at the cellular level to investigate how the host sinusoidal structures survived after lethal irradiation.

MATERIALS AND METHODS

Apoptosis and cell proliferation assays were performed on bone marrow sections at various time points during the first 2 weeks postirradiation to study the extent of damage to sinusoidal endothelial cells from lethal irradiation and to determine whether cell proliferation contributes to the recovery of the sinusoidal system.

RESULTS

Phosphorylated H2AX was present in both hematopoietic and sinusoidal endothelial cells 3 hours after irradiation demonstrating DNA damage. Three days after irradiation, some sinusoidal endothelial cells became terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling -positive, but were caspase-3 and in situ oligo ligation -negative, suggesting nonapoptotic DNA fragmentation. Clusters of sinusoidal endothelial cells that expressed Ki67 appeared 3 days after irradiation, and increased through day 7. These Ki67-positive endothelial cells were host-derived. Bromodeoxyuridine-positive endothelial cells were present in the Ki67-positive areas confirming endothelial cell replication. Twenty percent of the sinusoidal endothelial cells were lost by day 3 after irradiation. The total number of endothelial cells remained relatively unchanged between day 3 and day 14. These results demonstrate that lethal irradiation resulted in limited, nonapoptotic sinusoidal endothelial cell loss, followed by proliferation of preexisting host-derived mature sinusoidal endothelial cells. Our data suggest that DNA repair mechanisms and proliferation of host endothelial cells within the sinusoids are involved in maintenance of the structural integrity of the bone marrow vascular niche following lethal irradiation.