Quantification of apoptotic DNA fragmentation in a transformed uterine epithelial cell line, HRE-H9, using capillary electrophoresis with laser-induced fluorescence detector (CE-LIF)

Capillary electrophoresis analysis of hydrogen peroxide induced apoptosis in PC12 cells

Apoptosis is a highly regulated and controlled process of cell death that plays a fundamental role in many biological processes. Abnormal apoptosis of cells is closely related to some diseases such as cancer. Development of a simple and effective method to detect apoptosis is of great importance. In the present paper, capillary electrophoresis (CE) method was applied to distinguish cell apoptosis and necrosis of rat pheochromocytoma (PC12) cells treated by hydrogen peroxide by characterizing the DNA fragmentation. Firstly, effects of separation conditions (voltage, polymer concentration, temperature and injection time) on DNA separation were studied using 100 bp DNA ladders as the analyte. Under optimal separation condition (polyacrylamide coated capillaries: 57.5 cm x 75 microm i.d., effective length: 50 cm; running buffer: 1x TBE containing 2% PVP and 1.2% HEC; separation voltage: 5 kV; temperature: 25 degrees C; electrokinetic injection: 10 kV x 10 s), CE was used to monitor the progress of hydrogen peroxide induced apoptosis of PC12 cells by analyze DNA fragmentation. It was found that normal, apoptotic and neurotic cells had distinct DNA fragmentation patterns analyzed by CE. The results by CE were tested by other current methods (DAPI nuclei staining, flow cytometry analysis and TUNEL) to detect apoptosis and correlated well with those methods. Results show that CE can distinguish cell apoptosis and necrosis, quantify the degree of apoptosis in cells and have advantages of high efficiency, fast sample analysis speed, minute sample consumption and reliable results, which provides an accessorial method in the research of multiple diseases with abnormal apoptosis such as cancer and neurodegenerative diseases.

Exaggerated production of nitric oxide (NO) and increases in inducible NO-synthase mRNA levels induced by the pro-inflammatory cytokine interleukin-1beta in vascular smooth muscle cells of elderly rats

Nitric oxide (NO) is produced at high levels by inducible nitric oxide synthase (iNOS) during inflammation and other pathological conditions, contributing to development of cardiovascular diseases. The present study determined if aging affects the ability of interleukin-1beta (IL-1beta), a pro-inflammatory cytokine, to induce increased NO production (assessed by Griess reaction) and iNOS mRNA levels (assessed by RT-PCR/agarose gel electrophoresis) in vascular smooth muscle cells (VSMCs) from young (3-month-old) and elderly (20-22-month-old) rats. The VSMCs cells were used only in early passages (passages 0 and 1) to avoid phenotypic modulation. To uncover subtle differences in basal iNOS mRNA levels in VSMCs of young and elderly rats, RT-PCR products were also analyzed by a new ultrasensitive technique using capillary electrophoresis with laser-induced fluorescence detector (CE-LIF). IL-1beta (5 ng/ml) significantly (P < 0.05) increased NO production 3.7-fold in elderly female VSMCs and 6.7-fold in elderly male VSMCs, but had no detectable effect in young female and male VSMCs. Basal iNOS mRNA levels (assessed by RT-PCR/CE-LIF) were dramatically higher in VSMCs of elderly male rats compared to young ones. In general, VSMCs of elderly rats showed much greater sensitively to iNOS-inducing actions of IL-1beta. These data give new insight into effects of aging on iNOS expression in VSMCs, showing dramatic increases in both basal and stimulated iNOS mRNA levels, which may contribute to the development of vascular diseases in the elderly.

Preincubation with atrial natriuretic peptide protects NG108-15 cells against the toxic/proapoptotic effects of the nitric oxide donor S-nitroso- N-acetylpenicillamine

The TUNEL method is used to quantify the proapoptotic effects of an NO donor, S-nitroso- N-acetylpenicillamine (SNAP), in NG108-15 cells. Unlike sodium nitroprusside used in previous studies, SNAP does not release cyanide along with NO, thus NO toxicity was determined without concurrent cyanide toxicity. The present study also determined if pretreatment with ANP could protect against NO-induced apoptosis in NG108-15 cells. Cell death at 24 h following SNAP treatment was associated with apoptotic DNA fragmentation. SNAP at 0.5, 0.75, 1.0, and 2.0 mM caused significant (P<0.05) increases in the percentage of TUNEL-labeled cells from a control of 0.90% to 6.19%, 6.36%, 7.25%, and 15.1%, respectively. Thus, SNAP caused concentration-dependent induction of apoptosis in NG108-15 cells. SNAP-induced apoptosis was confirmed by morphological changes and increased levels of polynucleosome-sized fragments of DNA assessed by capillary electrophoresis. Preincubation for 24 h with ANP at 0.01, 0.1, and 1.0 microM, before the SNAP, significantly (P<0.05) decreased the percentage of labeled cells from 7.25% to 5.10%, 4.36%, and 3.24% in the presence of SNAP (1 mM) and from 15.1% to 7.91%, 6.64%, and 5.60% in the presence of SNAP (2 mM), respectively, representing protection of 24.0%, 34.0%, and 57.0% against SNAP (1 mM) and 26.0%, 37.0%, and 50.9% against SNAP (2 mM). Thus, prior activation of a cGMP-mediated neuroprotective mechanism induced by ANP appears to counterbalance, at least partially, the proapoptotic effects of excess NO. This neuroprotective mechanism involving cGMP may be especially important in protecting against the development of neurodegenerative diseases in which excess NO is thought to contribute to neuronal apoptosis.

Nitric oxide and cyclic GMP as pro- and anti-apoptotic agents

BACKGROUND

Previously we showed that atrial natriuretic peptide (ANP) increases cGMP production in PC12 (sympathetic-neuron-like) cells, cGMP elevations increase survival of hippocampal neurons during glutamate toxicity and ANP-induced cGMP elevations prolongs survival of stressed PC12 cells, all suggesting cGMP mediates anti-apoptotic/pro-survival effects in neural cells.

AIM

The objective was to use a new technology, capillary electrophoresis-laser-induced-fluorescence-detector (CE-LIF) to accurately measure nitric oxide (NO)-induced stimulation and ANP/cGMP-induced inhibition of apoptotic DNA fragmentation in PC12 and NG108-15 (cholinergic-neuron-like) cells.

METHODS

Apoptotic DNA fragmentation was quantified by CE-LIF.

RESULTS

Sodium nitroprusside (SNP, 0.1-1.0 mM, 24 hours), NO donor, increased apoptotic DNA fragmentation in NG108-15 cells, but not PC12 cells (both with serum). In serum-deprived PC12 cells, ANP at 1, 10 and 100 nM inhibited apoptotic DNA fragmentation by 75.8%, 84.7%, and 94.1%, respectively.

CONCLUSIONS

The data show that NO at higher levels induces apoptosis in NG108-15 cells, but not PC12 cells, indicating differences in susceptibility to NO-induced toxicity, and that ANP-induced cGMP elevation is a potent and effective inhibitor of apoptosis in PC12 cells. The data suggest that NO-induced cGMP elevations in certain neural cells (e.g. PC12 cells) provide a protective (anti-apoptotic) mechanism that counter-balances the pro-apoptotic actions of NO, thus helping to limit damage caused by NO.

Cyclooxygenase-2 regulates apoptosis in rat epididymis through prostaglandin D2

In previous studies, cyclooxygenase (COX)-1 and COX-2 isozymes have been detected in the rat epididymis. COX-1 mediates electrolyte and fluid secretion induced by a number of peptide hormones, including bradykinin, angiotensin, and endothelin, via local formation of prostaglandin (PG) E2; however, the physiological role of COX-2 remains largely unknown. Marked apoptotic cell death in the rat epididymis following androgen depletion has been reported. Because expression of both COX isozymes is dependent on androgen, we investigated whether these isozymes control apoptosis in the epididymis. Apoptosis was detected in rat epididymal epithelial cells by in situ staining using the TUNEL method and by the presence of internucleosomal DNA fragmentation using capillary electrophoresis with laser-induced fluorescence detection. Specific COX inhibitors were used to delineate the roles of the 2 isozymes. There was no significant apoptotic cell death in normal and specific COX-1 inhibitor (SC-560)-treated epididymal cells. However, application of a specific COX-2 inhibitor (NS-398) induced apoptosis in a dose- and time-dependent manner. A similar apoptotic effect of COX-2 inhibitor was seen in the in vivo study. The drastic DNA fragmentation induced by COX-2 inhibitor could be reversed completely by PGD2 and partially by PGE2. In addition, the protective effect of PGD2 against COX-2 inhibition was significantly blocked by a PGDP-receptor antagonist, BWA868C. These results indicate that the COX-2 products PGD2 and, to a lesser extent, PGE2 control apoptosis in cultured rat epididymal cells in vitro.