[Efficacy of simple continuous positive airway pressure on patients with obstructive sleep apnea].

Objective: To investigate the efficacy of simple device of continuous positive airway pressure (CPAP) in the treatment of obstructive sleep apnea (OSA). Methods: A double-blind study was performed on 53 OSA patients who received overnight simple CPAP and traditional CPAP in a random order during polysomnography. Pressure for CPAP treatment was manual titrated. The sleep apnea hypopnea index (AHI), arousal index (ArI), Oxygen desaturation Index (ODI), sleep structure and the preference for CPAP devices of the patients were observed. Results: AHI, ArI, ODI decreased significantly from 35.7 (18.1, 58.8)/h, (29.4±18.6)/h, 22.0 (13.9, 47.3)/h before treatment to 1.7 (0.7, 4.4)/h, (11.5±5.1) /h and 1.3 (0.4, 3.6)/h after treatment with simple CPAP, respectively (all P<0.05). There was no statistically significant difference in residual AHI [1.7 (0.7, 4.4)/h vs 1.9 (0.8, 4.3)/h], ArI [(11.5±5.1)/h vs (10.5±4.4)/h] and ODI [1.3 (0.4, 3.6)/h vs 1.3 (0.5, 4.2)/h] between treatment with simple CPAP and traditional CPAP (all P>0.05). The amount of time spent on deep sleep (stage Ⅲ) and rapid eye movement (REM) increased significantly from (6.2+ 6.6)% and (16.3+ 7.0)% before treatment to (11.7±8.5)% and (20.7±5.1)% during treatment with simple CPAP and (11.4±8.6)% and (20.9±5.0)% with traditional CPAP, respectively. The patients had no clear preference for two CPAP devices. Conclusion: Traditional CPAP can be replaced by the simple CPAP to treat patients with OSA.

Bcl-2-mediated resistance to apoptosis is associated with glutathione-induced inhibition of AP24 activation of nuclear DNA fragmentation.

Studies on the mechanism of apoptosis in this laboratory support a model in which signal transduction involving caspase 3 leads to activation of a serine protease called Mr 24,000 apoptotic protease (AP24), which then induces internucleosomal DNA fragmentation in the nucleus. This study examined the effect of Bcl-2 overexpression on activation of AP24 and the induction of DNA fragmentation by AP24 in isolated nuclei. It was demonstrated that overexpression of Bcl-2 in either HL-60 or PW leukemia cell lines suppressed activation of AP24 induced by either tumor necrosis factor or UV light and protected cells from apoptosis. Furthermore, nuclei isolated from Bcl-2-overexpressing cells were relatively resistant to internucleosomal DNA fragmentation induced by AP24 isolated from apoptotic cells. Bcl-2-overexpressing cells that were nutritionally depleted of glutathione (GSH) became sensitive to tumor necrosis factor- or UV light-induced activation of AP24 and underwent apoptotic cell death. Moreover, nuclei isolated from Bcl-2-overexpressing cells that were depleted of GSH became sensitive to AP24-induced DNA fragmentation. The addition of exogenous GSH blocked the proteolytic activity of AP24, as well as its ability to induce DNA fragmentation in normal isolated nuclei. These results indicate that Bcl-2 can attenuate at least two events in the AP24 apoptotic pathway: activation of AP24 and induction of DNA fragmentation by activated AP24. Furthermore, agents that deplete intracellular levels of GSH may have therapeutic use in the sensitization of Bcl-2-overexpressing cancer cells to apoptotic cell death.

Biochemical pathways of apoptosis: nicotinamide adenine dinucleotide-deficient cells are resistant to tumor necrosis factor or ultraviolet light activation of the 24-kD apoptotic protease and DNA fragmentation.

The function of nicotinamide adenine dinucleotide (NAD) and adenosine diphosphate (ADP) ribosylation reactions in the mechanism of apoptotic cell death is controversial, although one theory postulates an essential role for NAD depletion by poly-ADP-ribose polymerase. The present study examined the role of intracellular NAD in tumor necrosis factor (TNF) and ultraviolet (UV) light-induced activation of the 24-kD apoptotic protease (AP24) leading to internucleosomal DNA fragmentation and death. Our results demonstrate that nutritional depletion of NAD to undetectable levels in two leukemia lines (U937 and HL-60) renders them completely resistant to apoptosis. This was attributed to a block in the activation of AP24 and subsequent DNA cleavage. Normal cells show an elevation of ADP-ribosyl transferase (ADPRT) in both the cytosol and nucleus after exposure to TNF, but before DNA fragmentation. ADPRT activity as well as cell death was suppressed by an inhibitor specific for mono-ADPRT. Nuclei from NAD-depleted cells were still sensitive to DNA fragmentation induced by exogenous AP24, indicating a selective function for NAD upstream of AP24 activation in the apoptotic pathway. We confirmed a requirement for intracellular NAD, activation of ADPRT, and subsequent NAD depletion during apoptosis in KG1a, YAC-1, and BW1547 leukemia cell lines. However, this mechanism is not universal, since BJAB and Jurkat leukemia cells underwent apoptosis normally, even in the absence of detectable intracellular NAD. We conclude that TNF or UV light-induced apoptotic cell death is not due to NAD depletion in some leukemia cell lines. Rather, NAD-dependent reactions which may involve mono-ADPRT, function in signal transduction leading to activation of AP24, with subsequent DNA fragmentation and cell death.

Purification of a 24-kD protease from apoptotic tumor cells that activates DNA fragmentation.

We report the purification of a protease from tumor cells undergoing apoptosis that is involved in activating DNA fragmentation. Initial studies revealed that two inhibitors of serine proteases, N-1-tosylamide-2-phenylethylchloromethyl ketone and carbobenzoxy-Ala-Ala-borophe (DK120), suppressed tumor necrosis factor or ultraviolet (UV) light-induced DNA fragmentation in the U937 histiocytic lymphoma as well as UV light-induced DNA fragmentation in the BT-20 breast carcinoma, HL-60 myelocytic leukemia, and 3T3 fibroblasts. The protease was purified by affinity chromatography with DK120 as ligand and showed high activity on a synthetic substrate preferred by elastase-like enzymes (Ala-Ala-Pro-Val p-nitroanilide), but was inactive on the trypsin substrate, N-alpha-benzyloxycarbonyl-L-lysine thiobenzyl ester, or the chymotrypsin substrate, Ala-Ala-Pro-Phe p-nitroanilide. The activity of the DK120-binding protease purified from U937 cells undergoing apoptosis was increased approximately 10-fold over that recovered from normal cells. Further purification to homogeneity by heparin-Sepharose affinity chromatography followed by reverse phase high-performance liquid chromatography revealed a single band of 24 kD on a silver-stained sodium dodecyl sulfate gel. In addition to protease activity, the purified enzyme induced DNA fragmentation into multiples of 180 basepairs in isolated U937 nuclei. These findings suggest the 24-kD protease is a novel enzyme that activates DNA fragmentation in U937 cells undergoing apoptosis.

Experimental treatment of L-801 myeloid leukemia mice with low molecular weight natural tumor suppressor of human fetal brain origin.

In human fetal brain tissue there is a low molecular weight suppressor substance which can preferentially suppress murine myeloid leukemic cell (L-801) growth, but with less harmful effects on the growth of normal bone marrow hemopoietic stem cells (CFU-S) and granuloid/macrophage progenitors (CFU-GM) in vitro liquid or agar culture. Mice after inoculation of L-801 cells died within 10-17 days due to development of leukemia. After consecutive injections of the low molecular weight suppressor substance isolated from human fetal brain tissue some of the leukemic mice survived. No pathological changes were observed in the mice which survived longer than 100 days after inoculation of L-801 cells.

Translation of poly(A)+ mRNA encoding CFU-S proliferation stimulator of human fetal liver origin in Xenopus laevis oocytes.

Using the sodium dodecyl sulfate/chloroform/phenol method, total RNA was extracted from human fetal liver tissue with a yield of 870-1060 micrograms/g of tissue; mRNA was obtained after chromatography on an oligo(dT)-cellulose column. Experimental studies demonstrated the translation of a poly(A)+ mRNA encoding proliferation stimulator of human fetal liver origin in Xenopus laevis oocytes.