Activation of ion transport by combined effects of ionomycin, forskolin and phorbol ester on cultured HT-29cl.19A human colonocytes

The differentiated clone 19A of the HT-29 human colon carcinoma cell line was used as a model to study the intracellular electrophysiological effects of interaction of the cAMP, the protein kinase C (PKC) and the Ca2+ pathways, (a) A synergistic effect between ionomycin and forskolin was observed. From intracellular responses it was concluded that the synergistic effect is caused by activation of an apical Cl- conductance by protein kinase A and a basolateral K+ conductance by Ca2+. (b) A transient synergistic effect of ionomycin and the phorbol ester phorbol dibutyrate (PDB) was found. The decrease of the response appeared to be due to PKC-dependent inactivation of the basolateral K+ conductance. The synergism is caused by PKC-dependent increase of the apical Cl- conductance and Ca2+-dependent increase of the basolateral K+ conductance. (c) The effects of carbachol and PDB were not fully additive presumably because of their convergence on PKC activation, (d) Forskolin and P

Monitoring enteral nutrition efficacy in ICU patients: is there a place for the Brix value-derived fraction of enteral formula in gastric residual volume?

status: publishe

Protein tyrosine phosphorylation is involved in osmoregulation of ionic conductances

Using the human Intestine 407 cell line as a model, we investigated a possible role for tyrosine kinase(s) in regulating the ion efflux pathways induced by hyposmotic stimulation (regulatory volume decrease, RVD). Pretreatment of 125I(-)-and 86Rb(+)-loaded cells with the phosphotyrosine phosphatase inhibitor sodium orthovanadate (200 microM) potentiated isotope efflux triggered by mild hypotonicity (10-20%) but did not further increase the efflux in response to more vigorous osmotic stimulation (30% hypotonicity). The tyrosine kinase inhibitors herbimycin A and genistein largely reduced the osmoshock-induced efflux in both control and vanadate-pretreated cells, while not affecting calcium-activated 86Rb+ efflux. Potentiation of the RVD response by vanadate was confirmed by direct measurements of hypotonicity-induced changes in cell volume. Hypotonic shock alone triggered a rapid and transient increase in tyrosine phosphorylation of several proteins as well as phosphorylation of mitogen-activated protein kinase. Furthermore, the potentiating effects of vanadate on hypotonicity-induced ion efflux and mitogen-activated protein (MAP) kinase phosphorylation were mimicked by epidermal growth factor. Neither vanadate nor epidermal growth factor provoked a RVD-like ionic response under isotonic conditions. These results indicate that tyrosine phosphorylation is an essential step in the RVD response and suggest a novel role of growth factors in the cellular defense against osmotic stress

Clinical response correlates with 4-week postinjection ustekinumab concentrations in patients with moderate-to-severe psoriasis

Background: Cost‐effective use of biologicals is important. As drug concentrations have been linked to clinical outcomes, monitoring drug concentrations is a valuable tool to guide clinical decision‐making. A concentration–response relationship for ustekinumab at trough is uncertain owing to the contradictory results reported. Objectives: To investigate the relationship between 4‐week postinjection ustekinumab concentrations and clinical response in patients with psoriasis. Methods: Forty‐nine patients with moderate‐to‐severe psoriasis treated with 45 mg or 90 mg ustekinumab every 12 weeks for ≥ 16 weeks were included. Ustekinumab serum concentrations and anti‐ustekinumab antibodies were measured at week 4 after injection and disease severity was assessed by Psoriasis Area and Severity Index (PASI). Results: At week 4 after injection, a significantly negative correlation was observed between ustekinumab concentrations and absolute PASI score up to 5·9 μg mL−1 (ρ = –0·357, P = 0·032). Ustekinumab concentrations were higher in optimal responders (PASI ≤ 2) than in suboptimal responders (PASI > 2) (4·0 vs 2·8 μg mL−1, P = 0·036). The ustekinumab concentration threshold associated with optimal response was determined to be 3·6 μg mL−1 (area under the curve 0·71, sensitivity 86%, specificity 63%). Only one patient (2%) had anti‐ustekinumab antibodies. Psoriatic arthritis was identified as an independent predictor of higher PASI scores and higher ustekinumab concentrations (P = 0·003 and P = 0·048, respectively). Conclusions: A concentration–response relationship at week 4 after injection was observed for patients with psoriasis treated with ustekinumab. Monitoring 4‐week postinjection ustekinumab concentrations could timely identify underexposed patients who might benefit from treatment optimization