Abstract

Aims: Glucose evoked changes in profibrotic transforming growth factor-beta1 (TGFß1), increase connexin hemichannel mediated ATP release in kidney proximal tubule cells. With ATP linked to inflammation, we evaluated the efficacy of hemichannel blocker Peptide 5 in negating ATP induced inflammatory cytokine secretion in proximal tubule cells.

Methods: Primary human proximal tubular epithelial cells (hPTECs), and immortalised human kidney (HK2) cells were treated with TGFß1 (10ng/ml) ± Peptide5 (25µM) for 48hrs. Carboxyfluorescein (200µM) dye uptake and ATP biosensing determined hemichannel activity and ATP release respectively. Proteome arrays determined cytokine secretion.

Results: In TGFß1 treated hPTECs, carboxyfluorescein dye uptake decreased from 347.4±11.9%, (P<0.001, N=3) to 158.6±7.9% when co-incubated with Peptide 5. Parallel to this, ATP release increased from 0.16±0.1µM to 2.5±0.14µM (P<0.001, N=3) in TGF1 treated cells as compared to control. Peptide 5 significantly blunted this response, to 0.62±0.17µM (P<0.001, N=3). A proteome array determined the impact of Peptide 5 on secretion of 105 candidate chemokines and cytokines in TGFß1 treated primary cells. As an example, Peptide 5 significantly restored secretion of adiponectin from 163±8.0% (P<0.001, N=4) to 136±6.1% (P<0.05, N=4), granulocyte-macrophage colony-stimulating factor from 183±8.0% (P<0.001, N=4) to 111.3±5.9% (P<0.001, N=4) and interleukin 1-beta from 189±14.9 (P<0.001, N=4) to 109±9.6% (P<0.001, N=4) in TGF-ß1 treated hPTECs, as compared to control.

Conclusion: Glucose evoked changes in TGFß1 increase hemichannel mediated ATP release. Hemichannel blocker; Peptide 5 blocks ATP release and downstream cytokine and chemokine secretion, suggesting that Peptide 5 may be of future therapeutic potential in targeting inflammation of the diabetic kidney.