Pulmonary toxicity of inhaled aerosolized prostacyclin therapy--an observational study

Large white/landrace piglets (mass 11 to 21 kg) were exposed to aerosolized alkaline glycine diluent (n = 2) or inhaled aerosolized prostacyclin (n = 2) for five to eight hours. Pigs receiving these aerosols developed mild acute sterile tracheitis, involving the superficial layers of the trachea, shown histologically and ultrastructurally. Pigs receiving the diluent aerosol also showed mild inflammatory changes in the bronchioles. These findings suggest caution with the use of high volumes of aerosolized alkaline glycine diluent during inhaled aerosolized prostacyclin therapy.

A splice variant of the ITF-2 transcript encodes a transcription factor that inhibits MyoD activity

Proteins of the basic helix-loop-helix (bHLH) family are transcription factors that bind DNA containing the E box motif (CANNTG) found in the promoters of many muscle-specific genes. ITF-2 is a bHLH protein with widespread expression that is thought to form active heterodimers with MyoD, a muscle-specific bHLH transcription factor. We have isolated cDNAs derived from two alternatively spliced forms of mouse ITF-2, termed MITF-2A and -2B. These proteins differ in their N termini. Neither MITF-2A nor -2B transactivated the cardiac alpha-actin promoter, which contains an E box, when transfected into nonmuscle cells. In fact, MITF-2B inhibited MyoD activation of the cardiac alpha-actin promoter. This inhibitory activity required the N-terminal 83 amino acids since MITF-2A showed no inhibitory activity, and a mutant MITF-2B with deletion of the N-terminal 83 amino acids failed to inhibit MyoD-mediated transcriptional activation. MyoD activity was also inhibited by Id, a HLH protein, and this inhibition was reversed by the addition of excess E12 or MITF-2A. However, the inhibition of MyoD activity by MITF-2B was not reversed with E12 or MITF-2A. While Id is thought to inhibit MyoD by binding and sequestering potential dimerization partners, MITF-2B appears to inhibit MyoD activity by forming an inactive heterodimer with MyoD. Thus, differentially spliced transcripts of mouse ITF-2 encode different proteins that appear to dimerize with MyoD and activate or repress transcription.