Metabolic acidosis may be as protective as hypercapnic acidosis in an ex-vivo model of severe ventilator-induced lung injury: a pilot study

<p>Abstract</p> <p>Background</p> <p>There is mounting experimental evidence that hypercapnic acidosis protects against lung injury. However, it is unclear if acidosis <it>per se </it>rather than hypercapnia is responsible for this beneficial effect. Therefore, we sought to evaluate the effects of hypercapnic (respiratory) versus normocapnic (metabolic) acidosis in an ex vivo model of ventilator-induced lung injury (VILI).</p> <p>Methods</p> <p>Sixty New Zealand white rabbit ventilated and perfused heart-lung preparations were used. Six study groups were evaluated. Respiratory acidosis (RA), metabolic acidosis (MA) and normocapnic-normoxic (Control - C) groups were randomized into high and low peak inspiratory pressures, respectively. Each preparation was ventilated for 1 hour according to a standardized ventilation protocol. Lung injury was evaluated by means of pulmonary edema formation (weight gain), changes in ultrafiltration coefficient, mean pulmonary artery pressure changes as well as histological alterations.</p> <p>Results</p> <p>HPC group gained significantly greater weight than HPMA, HPRA and all three LP groups (P = 0.024), while no difference was observed between HPMA and HPRA groups regarding weight gain. Neither group differ on ultrafiltration coefficient. HPMA group experienced greater increase in the mean pulmonary artery pressure at 20 min (P = 0.0276) and 40 min (P = 0.0012) compared with all other groups. Histology scores were significantly greater in HP vs. LP groups (p < 0.001).</p> <p>Conclusions</p> <p>In our experimental VILI model both metabolic acidosis and hypercapnic acidosis attenuated VILI-induced pulmonary edema implying a mechanism other than possible synergistic effects of acidosis with CO2 for VILI attenuation.</p

Myb and ets proteins are candidate regulators of c-kit expression in human hematopoietic cells.

Kit is a tyrosine kinase receptor that plays an important role in human hematopoietic cell growth. The promoter elements that modulate the gene's expression have not been extensively studied. Because of c-kit's acknowledged importance in hematopoiesis, we sought to address this issue in more detail. To perform these studies we analyzed a human c-kit 5' flanking fragment approximately 1 kilobase in length. Deletion constructs showed a region approximately 139 nucleotides upstream from the translation initiation site that was critical for promoter activity. A region containing a potential silencing element was also identified. Sequence analysis indicated several potential Myb- and Ets-binding sites. The functional significance of these sites was explored by showing that both wild-type Myb and Ets-2 protein, but not a DNA binding-deficient Myb mutant protein, bound to distinct 5' flanking fragments that included these sites. Furthermore, binding of recombinant Myb and Ets-2 protein to these fragments could be competed with an excess of double stranded oligodeoxynucleotides containing canonical, but not mutated, Myb- or Ets-binding sites. We also showed that the 5' flanking region of c-kit exhibited promoter activity in nonhematopoietic cells only when the cells were transfected with c-myb or ets-2 expression vectors. Moreover, Myb and Ets-2 coexpression in such cells augmented transactivation of c-kit promoter constructs in comparison to that observed in cells transfected with either construct alone. Promoter constructs lacking various Myb and Ets sites deleted were much less effective in this same system. Finally, Myb and Ets-2 mRNA expression was detected in CD34+, Kit low as well as CD34+, Kit bright cells. In aggregate, these data further define the human c-kit promoter's functional anatomy and suggest that Myb and Ets proteins play an important, perhaps cooperative, role in regulating expression of this critical hematopoietic cell receptor