Regulation of cell survival by sphingosine-1-phosphate receptor S1P1 via reciprocal ERK-dependent suppression of bim and PI-3-kinase/protein kinase C-mediated upregulation of Mcl-1

Although the ability of bioactive lipid sphingosine-1-phosphate (S1P) to positively regulate anti-apoptotic/pro-survival responses by binding to S1P1 is well known, the molecular mechanisms remain unclear. Here we demonstrate that expression of S1P1 renders CCL39 lung fibroblasts resistant to apoptosis following growth factor withdrawal. Resistance to apoptosis was associated with attenuated accumulation of pro-apoptotic BH3-only protein Bim. However, although blockade of extracellular signal-regulated kinase (ERK) activation could reverse S1P1-mediated suppression of Bim accumulation, inhibition of caspase-3 cleavage was unaffected. Instead S1P1-mediated inhibition of caspase-3 cleavage was reversed by inhibition of phosphatidylinositol-3-kinase (PI3K) and protein kinase C (PKC), which had no effect on S1P1 regulation of Bim. However, S1P1 suppression of caspase-3 was associated with increased expression of anti-apoptotic protein Mcl-1, the expression of which was also reduced by inhibition of PI3K and PKC. A role for the induction of Mcl-1 in regulating endogenous S1P receptor-dependent pro-survival responses in human umbilical vein endothelial cells was confirmed using S1P receptor agonist FTY720-phosphate (FTY720P). FTY720P induced a transient accumulation of Mcl-1 that was associated with a delayed onset of caspase-3 cleavage following growth factor withdrawal, whereas Mcl-1 knockdown was sufficient to enhance caspase-3 cleavage even in the presence of FTY720P. Consistent with a pro-survival role of S1P1 in disease, analysis of tissue microarrays from ER+ breast cancer patients revealed a significant correlation between S1P1 expression and tumour cell survival. In these tumours, S1P1 expression and cancer cell survival were correlated with increased activation of ERK, but not the PI3K/PKB pathway. In summary, pro-survival/anti-apoptotic signalling from S1P1 is intimately linked to its ability to promote the accumulation of pro-survival protein Mcl-1 and downregulation of pro-apoptotic BH3-only protein Bim via distinct signalling pathways. However, the functional importance of each pathway is dependent on the specific cellular context

Changes in health-related quality of life among older adults aging with long-term spinal cord injury

Study design: Cross-sectional and longitudinal. Objectives: To (i) describe health-related quality of life (HRQoL) and changes over 6 years in older adults aging with long-term spinal cord injury (SCI) and (ii) investigate how changes in HRQoL are associated with age, gender, and injury characteristics. Setting: Community in southern Sweden. Methods: From the initial 123 participants (years 2011–2012) in the Swedish Aging with Spinal Cord Injury Study (SASCIS), 77 individuals (32% women, C1-L3, AIS A–D, median age 66 years, median time since injury 31 years, 30% complete injuries) were assessed 6 years later. HRQoL was rated with the Spinal Cord Injury Quality of Life Questionnaire (SCI QL-23). Associations were investigated using multivariable linear regression analyses. Results: The median rating of global QoL (scale range 0–100) was relatively high at both assessments (67 and 83, respectively). There was a large variability in all HRQoL-domains and no significant changes over 6 years. As compared to an AIS D injury, a tetraplegia AIS A–C injury and tetraplegia and paraplegia AIS A–C injuries were associated with positive change in depressive symptoms and global QoL, respectively. Conclusions: Older adults aging with long-term SCI show large variations in all HRQoL-domains and have the potential to maintain a high and stable level of HRQoL over time. Persons with AIS D injuries may need increased attention to mitigate negative changes in depressive symptoms and global QoL. Further studies are needed to identify modifiable factors associated with changes in HRQoL in older adults aging with long-term SCI