Transforming growth factor‐β1 enhances the antifibrinolytic and prothrombotic state of growing endothelial cells in a cell cycle‐specific manner

Molecular Mechanisms Responsible for Neuron-Derived Conditioned Medium (NCM)-Mediated Protection of Ischemic Brain

The protective value of neuron-derived conditioned medium (NCM) in cerebral ischemia and the underlying mechanism(s) responsible for NCM-mediated brain protection against cerebral ischemia were investigated in the study. NCM was first collected from the neuronal culture growing under the in vitro ischemic condition (glucose-, oxygen- and serum-deprivation or GOSD) for 2, 4 or 6 h. Through the focal cerebral ischemia (bilateral CCAO/unilateral MCAO) animal model, we discovered that ischemia/reperfusion (I/R)-induced brain infarction was significantly reduced by NCM, given directly into the cistern magna at the end of 90 min of CCAO/MCAO. Immunoblocking and chemical blocking strategies were applied in the in vitro ischemic studies to show that NCM supplement could protect microglia, astrocytes and neurons from GOSD-induced cell death, in a growth factor (TGFβ1, NT-3 and GDNF) and p-ERK dependent manner. Brain injection with TGFβ1, NT3, GDNF and ERK agonist (DADS) alone or in combination, therefore also significantly decreased the infarct volume of ischemic brain. Moreover, NCM could inhibit ROS but stimulate IL-1β release from GOSD-treated microglia and limit the infiltration of IL-β-positive microglia into the core area of ischemic brain, revealing the anti-oxidant and anti-inflammatory activities of NCM. In overall, NCM-mediated brain protection against cerebral ischemia has been demonstrated for the first time in S.D. rats, due to its anti-apoptotic, anti-oxidant and potentially anti-glutamate activities (NCM-induced IL-1β can inhibit the glutamate-mediated neurotoxicity) and restriction upon the infiltration of inflammatory microglia into the core area of ischemic brain. The therapeutic potentials of NCM, TGFβ1, GDNF, NT-3 and DADS in the control of cerebral ischemia in human therefore have been suggested and require further investigation.

Expression of papillomavirus L1 proteins regulated by authentic gene codon usage is favoured in G2/M-like cells in differentiating keratinocytes

We investigated whether differentiation-dependent expression of papillomavirus (PV) L1 genes is influenced by the cell cycle state in keratinocytes (KCs) grown in vitro or in vivo. In primary keratinocytes, flow cytometry revealed a clear shift from predominantly G0/G1 to G2/M cells from day 1 to day 7, with a three-fold increase in G2/M-like cells in day 7 keratinocytes that showed approximately 50% of the cells expressed a terminal differentiation marker involucrin. The correlation between the levels of the L1 proteins expressed from authentic (Nat) L1 genes of HPV6b and BPV1 and the frequencies of the G2/M-like KCs was significantly positive, while in contrast, a significantly negative correlation in the levels of L1 proteins expressed from codon-modified (Mod) L1 genes of HPV6b and BPV1 with the frequencies of the G2/M-like KCs was observed. Experiments using cell cycle arrest reagents (all-trans retinoic acid (RA) and colchicine) confirmed that L1 proteins expressed from PV Nat L1 genes were facilitated in G2/M-like KCs upon differentiation. Using immunofluorescence microscopy, it appears that L1 proteins from PV Nat L1 genes were co-expressed with cyclin B1, while the L1 proteins expressed from PV Mod L1 genes were preferentially associated with cyclin D2 in KCs in vitro and in mouse skin. Our results demonstrate that (1) expression of the L1 proteins from Nat L1 genes of HPV6b and BPV1 that have strong codon usage bias with A or T at codon third position dependent on KC differentiation is favoured by the G2/M-like environment and (2) codon modifications can alter the cell differentiation-dependent and cell cycle-associated patterns of expression of the PV L1 proteins in KCs.