Inhibition of AKT signalling by benzoxazine derivative LTUR6 through the modulation of downstream kinases.

Many compounds structurally similar to chromones have been developed to enhance the sensitizing effect of cancer cells to chemotherapeutic agents. Most of these compounds have been shown to promote this sensitization by targeting the repair pathways. One such compound is LTUR6, which enhances the sensitization of doxorubicin to colon cancer cells HT29, by inhibiting the phosphorylation of the double stranded break (DSB) repair enzyme AKT. The downstream regulatory targets of AKT that enhance doxorubicin mediated cytotoxicity in the presence of LTUR6 remains elusive. In this study, we performed comparative analyses of 43 kinase phosphorylation sites using the human phospho-kinase array proteome profiler. Results revealed altered expression levels of multiple proteins that regulated apoptotic signalling pathways. Increased activation of mTOR, RSK1/2/3, p38α and PRAS40 after combination treatment with LTUR6 and doxorubicin over doxorubicin alone was observed. This study provides a deeper insight into the key proteins involved and presents a novel molecular pathway.

Role of a novel benzoxazine derivative in the chemosensitization of colon cancer.

The concept to fight against tumour resistance is to use chemosensitizers that selectively sensitize tumour cells to chemotherapeutic drugs without affecting normal tissue. In this study, the chemosensitizing potential of a novel benzoxazine derivative in combination with Doxorubicin, a DNA damaging chemotherapeutic drug was evaluated. The results of this study showed that the compound LTUR6 is a potent chemosensitizer of Doxorubicin in colon cancer cell lines, HCT116 and HT29. It was also observed that LTUR6 delayed the resolution of Doxorubicin-induced γH2AX, a specific marker of unrepaired DNA DSB, and prolonged cell cycle arrest in both cell lines. This eventually led to DNA fragmentation, caspase activation and ultimately apoptosis in LTUR6 treated cell lines. Results of western blot analysis revealed that LTUR6 significantly inhibited the phosphorylation of DSB repair enzyme AKT, in response to Doxorubicin-induced DSB. We propose that the chemosensitization observed following inhibition of PI3K is likely due to the involvement of a number of downstream targets of AKT.

Methylglyoxal couples metabolic and translational control of Notch signalling in mammalian neural stem cells.

Gene regulation and metabolism are two fundamental processes that coordinate the self-renewal and differentiation of neural precursor cells (NPCs) in the developing mammalian brain. However, little is known about how metabolic signals instruct gene expression to control NPC homeostasis. Here, we show that methylglyoxal, a glycolytic intermediate metabolite, modulates Notch signalling to regulate NPC fate decision. We find that increased methylglyoxal suppresses the translation of Notch1 receptor mRNA in mouse and human NPCs, which is mediated by binding of the glycolytic enzyme GAPDH to an AU-rich region within Notch1 3'UTR. Interestingly, methylglyoxal inhibits the enzymatic activity of GAPDH and engages it as an RNA-binding protein to suppress Notch1 translation. Reducing GAPDH levels or restoring Notch signalling rescues methylglyoxal-induced NPC depletion and premature differentiation in the developing mouse cortex. Taken together, our data indicates that methylglyoxal couples the metabolic and translational control of Notch signalling to control NPC homeostasis.

Spinal Cord Disruption Is Associated with a Loss of Cushing-Like Blood Pressure Interactions.

The capacity of the cerebrovasculature to buffer changes in blood pressure (BP) likely plays an important role in the prevention of stroke, which is three- to fourfold more common after spinal cord injury (SCI). Although the directional relationship between BP and cerebral blood flow (CBF) has traditionally been thought to travel solely from BP to CBF, a Cushing-like mechanism functioning in the inverse direction, in which changes in CBF influence BP, has recently been revealed using Granger causality analysis. Although both CBF buffering of BP and the Cushing-like mechanism are influenced by the sympathetic nervous system, we do not understand the impact of disruption of descending sympathetic pathways within the spinal cord, caused by cervical SCI on these regulatory systems. We hypothesized that people with cervical SCI would have greater BP to CBF transmission, as well as a reduced Cushing-like mechanism. The directional relationships between mean arterial BP (MAP; Finometer® PRO) and middle cerebral artery blood velocity (MCAv; transcranial Doppler) were assessed at rest in 14 cervical SCI subjects and 16 uninjured individuals using Granger causality analysis, while also accounting for end-tidal CO2 tension. Those with SCI exhibited 66% increased forward MAP→MCAv information transmission as compared with the uninjured group (p = 0.0003), indicating reduced cerebrovascular buffering of BP, and did not have a predominant backward Cushing-like MCAv→MAP phenotype. These results indicate that both forward and backward communication between BP and CBF are influenced by SCI, which may be associated with impaired cerebrovascular BP buffering after SCI as well as widespread BP instability.