Signalling of ERK1/2, P38MAPK and P90RSK in HIV-associated pre-eclampsia.

Due to their significance in trophoblast differentiation and survival, we evaluated the expression of the cell signalling molecules; Extracellular signal-regulated kinase 1/2 (ERK1/2), Mitogen Activated Protein Kinase 38 (MAPK38) and p90 ribosomal protein S6 kinase (p90 RSK) in buffy coat samples. Eighty pregnant women attending a large hospital in Durban, South Africa were assigned into normotensive and pre-eclamptic groups and further stratified by their HIV status. The degree of phosphorylation of the analytes was determined using the Bio-Plex ProTM Cell Signalling Immunoassay. There was a significantly lower protein concentration of the analytes in the pre-eclamptic versus the normotensive patients, irrespective of HIV status (p < .0001). Also, there was no significant difference in expression of ERK1/2 (p = .4369), p38MAPK (p = .4720) and p90 RSK (p = .0188), according to HIV status. This study demonstrates a down-regulation of ERK1/2, p38MAPK and p90RSK prosurvival markers in pre-eclampsia. This implicates the involvement of the MAPK pathway in the pathogenesis of preeclampsia. Activation of these pathways may prove useful in increasing the body of evidence on prevention of placenta dysfunction and apoptosis. Impact statement What is already known on this subject? Preeclampsia occurring in co-morbidity with HIV is a public health problem among pregnant, black South-African women. There have been conflicting theories regarding the predisposition to the development of preeclampsia as a result of compromised immune response due to HIV infection. In normal pregnancies, the MAPK pathway plays a significant role in molecular processes involved in the cells including survival and differentiation of the placental trophoblast. ERK1/2, p38MAPK and p90RSK are members of the MAPK family, which are pro-apoptotic. Inhibition in the signalling of MAPKs has been found to result in oxidative stress, a process which contributes to the defective trophoblast invasion seen in preeclampsia. What do the results of this study add? The results from this study showed that there is no relationship between HIV infection and an increased predisposition to the development of preeclampsia. In addition, this study highlights a downregulation in the expression of ERK1/2, p38 MAPK and p90RSK in preeclampsia. What are the implications of these findings for clinical practice and/or further research? These findings demonstrate the potential of these analytes as biomarkers for the diagnosis of preeclampsia. Also, this may serve as a framework for further research in the prevention of preeclampsia by elucidating more on the pathway.

Antitumor efficacy of intermittent treatment schedules with the rapamycin derivative RAD001 correlates with prolonged inactivation of ribosomal protein S6 kinase 1 in peripheral blood mononuclear cells.

The orally bioavailable rapamycin derivative RAD001 (everolimus) targets the mammalian target of rapamycin pathway and possesses potent immunosuppressive and anticancer activities. Here, the antitumor activity of RAD001 was evaluated in the CA20948 syngeneic rat pancreatic tumor model. RAD001 demonstrated dose-dependent antitumor activity with daily and weekly administration schedules; statistically significant antitumor effects were observed with 2.5 and 0.5 mg/kg RAD001 administered daily [treated tumor versus control tumor size (T/C), 23% and 23-30%, respectively], with 3-5 mg/kg RAD001 administered once weekly (T/C, 14-36%), or with 5 mg/kg RAD001 administered twice weekly (T/C, 36%). These schedules were well tolerated and exhibited antitumor potency similar to that of the cytotoxic agent 5-fluorouracil (T/C, 23%). Moreover, the efficacy of intermittent treatment schedules suggests a therapeutic window allowing differentiation of antitumor activity from the immunosuppressive properties of this agent. Detailed biochemical profiling of mammalian target of rapamycin signaling in tumors, skin, and peripheral blood mononuclear cells (PBMCs), after a single administration of 5 mg/kg RAD001, indicated that RAD001 treatment blocked phosphorylation of the translational repressor eukaryotic initiation factor 4E-binding protein 1 and inactivated the translational activator ribosomal protein S6 kinase 1 (S6K1). The efficacy of intermittent treatment schedules was associated with prolonged inactivation of S6K1 in tumors and surrogate tissues (> or =72 h). Furthermore, detailed analysis of the dose dependency of weekly treatment schedules demonstrated a correlation between antitumor efficacy and prolonged effects (> or =7 days) on PBMC-derived S6K1 activity. Analysis of human PBMCs revealed that S6K1 also underwent a concentration-dependent inactivation after RAD001 treatment ex vivo (>95% inactivation with 20 nM RAD001). In contrast, human PBMC-derived eukaryotic initiation factor 4E-binding protein 1 was present predominantly in the hypophosphorylated form and was unaffected by RAD001 treatment. Taken together, these results demonstrate a correlation between the antitumor efficacy of intermittent RAD001 treatment schedules and prolonged S6K1 inactivation in PBMCs and suggest that long-term monitoring of PBMC-derived S6K1 activity levels could be used for assessing RAD001 treatment schedules in cancer patients.