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Biomedical subjects

I R Witherden

Publications and source records attributed to I R Witherden.

6 recordsLinked to original sources
PubMed2006

Direct effects of dexamethasone on human podocytes.

Glucocorticoids are widely used in the treatment of human glomerular diseases, but their mode of action is poorly understood particularly in steroid-sensitive nephrotic syndrome, which is most common in childhood and is characterized by a lack of inflammation in the kidney. The podocyte is a key cell in the glomerulus in health and disease: until recently, human podocytes have been difficult to study in vitro. We have developed a conditionally immortalized human podocyte cell line transfected with a temperature-sensitive simian virus 40 transgene: when the transgene is inactivated in vitro, these cells adopt the phenotype of differentiated podocytes. We have used these cells to evaluate, using immunocytochemistry, reverse transcriptase-polymerase chain reaction, and Western blotting, direct effects of the glucocorticoid dexamethasone at concentrations designed to mimic in vivo therapeutic corticosteroid levels. Dexamethasone upregulated expression of nephrin and tubulin-alpha, and downregulated vascular endothelial growth factor. Effects on cell cycle were complex with downregulation of cyclin kinase inhibitor p21 and augmentation of podocyte survival, without any effect on apoptosis. We report cytokine production by human podocytes, especially interleukin (IL)-6 and -8; IL-6 expression was suppressed by dexamethasone. These potent direct effects on podocytes illustrate a novel mode of action of glucocorticoids and suggest potential new therapeutic strategies for glomerular disease.

Antigens, Polyomavirus Transforming↗
PubMed2005

Prospects in NSAID-derived chemoprevention of colorectal cancer.

There is strong evidence for an important role for increased COX (cyclo-oxygenase)-2 expression and PG (prostaglandin) E2 production in colorectal tumorigenesis. PGE(2) acts through four E-prostanoid receptors (EP1-4). COX-2 has therefore become a target for the potential chemoprevention and therapy of colorectal cancer. However, any therapeutic/preventive strategy has the potential to have an impact on physiological processes and hence result in side effects. General COX (COX-1 and -2) inhibition by traditional NSAIDs (non-steroidal anti-inflammatory drugs), such as aspirin, although chemopreventive, has some side effects, as do some conventional COX-2-selective NSAIDs. As PGE2 is thought to be the major PG species responsible for promoting colorectal tumorigenesis, research is being directed to a number of protein targets downstream of COX-2 that might allow the selective inhibition of the tumour-promoting activities of PGE2, while minimizing the associated adverse events. The PGE synthases and E-prostanoid receptors (EP1-4) have therefore recently attracted considerable interest as potential novel targets for the prevention/therapy of colorectal cancer. Selective (and possibly combinatorial) inhibition of the synthesis and signalling of those PGs most highly associated with colorectal tumorigenesis may have some advantages over COX-2-selective inhibitors.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1999

Lung type II cell and macrophage annexin I release: differential effects of two glucocorticoids.

Annexin I (lipocortin 1) is abundant in lung secretions. Concentrations rise after oral glucocorticoid, but the effect of inhaled budesonide on annexin I release is unknown. Extracellular annexin I in bronchoalveolar lavage fluid (BALF) from 11 asthmatic patients was unaffected by inhaled budesonide (800 microgramgs twice daily for 4 wk; mean after budesonide, 110 ng/mg albumin; after placebo, 107 ng/mg albumin). Rat alveolar macrophages (AMs) and alveolar epithelial type II (ATII) cells were cultured alone and with budesonide or dexamethasone. Mean basal concentrations of cellular (3.5 ng/10(6) AMs; 4.4 ng/10(6) ATII cells) and secreted (1. 4 ng/10(6) AMs; 1.8 ng/10(6) ATII cells) annexin I were similar in AMs and ATII cells. Although budesonide subdued annexin I secretion from both cell types, dexamethasone stimulated annexin I release. Annexin I release from ATII cells peaked at 10(-7) M dexamethasone but at 10(-3) M dexamethasone from AMs. Thus, at low concentrations of dexamethasone, ATII cells probably contribute more annexin I to respiratory tract secretions than AMs, although at high concentrations, both cells probably contribute. The study demonstrates previously undescribed differences between glucocorticoids and between AMs and ATII cells with respect to annexin I regulation.

Administration, Inhalation↗
PubMed1998

Reduction of nitric oxide release from alveolar macrophages by a lipocortin peptide.

Nitric oxide (NO), produced by alveolar macrophages (AM) is used as a marker of respiratory tract inflammation. Lipocortin 1 (Lc-1) is an anti-inflammatory, glucocorticoid-inducible protein. The current aims were to determine whether (a) an Lc-1-derived peptide, Ac2-26, inhibited lipopolysaccharide (LPS)-induced NO release by primary AM in vitro and (b) the inhibitory action of dexamethasone was Lc-1-dependent. LPS treatment stimulated NO release from rat AM. Ac2-26 had little effect on unstimulated release, but suppressed LPS-stimulated release at concentrations > or =320 nM (320 nM, 10 +/- 3%; 3.2 microM, 15 +/- 3%; 32 microM, 27 +/- 4% NO inhibited, mean +/- SEM, n = 6). Inhibition by dexamethasone of NO release was unaffected by neutralizing anti-Lc-1 indicating that this action is Lc-1-independent in primary AM. Nevertheless inhibition of NO release by Ac2-26 (80 microM) was similar to that of 1 microM dexamethasone (Ac2-26, 40 +/- 6%; dexamethasone, 48 +/- 6% NO inhibited, mean +/- SEM, n = 6).

Animals↗