The isoflavonoids genistein and quercetin activate different stress signaling pathways as shown by analysis of site-specific phosphorylation of ATM, p53 and histone H2AX

The ataxia-telangiectasia mutated (ATM) protein kinase is activated in response to ionizing radiation (IR) and activates downstream DNA-damage signaling pathways. Although the role of ATM in the cellular response to ionizing radiation has been well characterized, its role in response to other DNA-damaging agents is less well defined. We previously showed that genistein, a naturally occurring isoflavonoid, induced increased ATM protein kinase activity, ATM-dependent phosphorylation of p53 on serine 15 and activation of the DNA-binding properties of p53. Here. we show that genistein also induces phosphorylation of p53 at serines 6, 9, 20,46, and 392, and that genistein-induced accumulation and phosphorylation of p53 is reduced in two ATM-deficient human cell lines. Also, we show that genistein induces phosphorylation of ATM on serine 1981 and phosphorylation of histone H2AX on serine 139. The related bioflavonoids, daidzein and biochanin A, did not induce either phosphorylation of p53 or ATM at these sites. Like genistein, quercetin induced phosphorylation of ATM on serine 198 1, and ATM-dependent phosphorylation of histone H2AX on serine 139; however, p53 accumulation and phosphorylation on serines 6, 9, 15, 20, 46, and 392 occurred in ATM-deficient cells, indicating that ATM is not required for quercetin-induced phosphorylation of p53. Our data suggest that genistein and quercetin induce different DNA-damage induced signaling pathways that, in the case of genistein, are highly ATM-dependent but, in the case of quercetin, may be ATM-dependent only for some downstream targets. (C) 2003 Elsevier B.V. All rights reserved.

Evaluation of random plasma cortisol and the low dose corticotropin test as indicators of adrenal secretory capacity in critically ill patients: A prospective study

It is unclear whether a random plasma cortisol measurement and the corticotropin (ACTH) test adequately reflect glucocorticoid secretory capacity in critical illness. This study aimed to determine whether these tests provide information representative of the 24 hour period. Plasma cortisol was measured hourly for 24 hours in 21 critically ill septic patients followed by a corticotropin test with 1 μ g dose administered intravenously. Serum and urine were analysed for ACTH and free cortisol respectively. Marked hourly variability in plasma cortisol was evident (coefficient of variation 8-30%) with no demonstrable circadian rhythm. The individual mean plasma cortisol concentrations ranged from 286 59 nmol/l to 796 &PLUSMN; 83 nmol/l. The 24 hour mean plasma cortisol was strongly correlated with both random plasma cortisol (r(2) 0.9, P< 0.0001) and the cortisol response to corticotropin (r(2) 0.72, P< 0.001). Only nine percent of patients increased their plasma cortisol by 250 nmol/l after corticotropin (euadrenal response). However, 35% of non-responders had spontaneous hourly rises > 250 nmol/l thus highlighting the limitations of a single point corticotropin test. Urinary free cortisol was elevated (865&PLUSMN; 937 nmol) in both corticotropin responders and non-responders suggesting elevated plasma free cortisol. No significant relationship was demonstrable between plasma cortisol and ACTH. We conclude that although random cortisol measurements and the low dose corticotropin tests reliably reflect the 24 hour mean cortisol in critical illness, they do not take into account the pulsatile nature of cortisol secretion. Consequently, there is the potential for erroneous conclusions about adrenal function based on a single measurement. We suggest that caution be exercised when drawing conclusions on the adequacy of adrenal function based on a single random plasma cortisol or the corticotropin test.

Cutting edge: Species-specific TLR9-mediated recognition of CpG and non-CpG phosphorothioate-modified ohgonucleotides

Different DNA motifs are required for optimal stimulation Of mouse and human immune cells by CpG oligode-oxynucleotides (ODN). These species differences presumably reflect sequence differences in TLR9, the CPG DNA receptor. In this study, we show that this sequence specificity is restricted to phosphorothioate (PS)-modified ODN and is not observed when a natural phosphodiester backbone is used. Thus, human and mouse cells have not evolved to recognize different CpG motifs in natural DNA. Nonoptimal PS-ODN (i.e., mouse CpG motif on human cells and vice versa) gave delayed and less sustained phosphorylation of p38 AWK than optimal motifs. When the CpG dinucleotide was inverted to GC In each ODN some residual activity of the PS-ODN was retained in a species-specific, TLR-9-dependent manner. Thus, TLR9 may he responsible for mediating many published CpG-independent responses to PS-ODN.

Cross-language Perception of Word-final Stops by Native Vietnamese Listeners: Preliminary Results on the Role of Specific, Non-native Phonetic Experience

This study examined the discrimination of word-final stop contrasts (/p/-/t/, /p/-/k/, /t/-/k/) in English and Thai by 12 listeners who speak Vietnamese as their first language (L1). Vietnamese shares specific phonetic realization of stops with Thai, i.e., unreleased final stop and differs from English which allows both released and unreleased final stops. These 12 native Vietnamese (NV) listeners’ discrimination accuracy was compared to that of the two listener groups (Australian English (AE), native Thai (NT)) tested in previous studies. The NV group was less accurate than the native group in discriminating both English and Thai stop contrasts. In particular, for the Thai /t/-/k/ contrast, they were significantly less accurate than the AE listeners. The present findings suggest that experience with specific (i.e., unreleased) and native phonetic realization of sounds may be essential in accurate discrimination of final stop contrasts. The effect of L1 dialect on cross-language speech perception is discussed.