Interleukin 6: a functional and structural in vitro modulator of beta-cells from islets of Langerhans

Area of Science:

• Endocrinology
• Immunology
• Cell Biology

Background:

• Interleukin-6 (IL-6) is a cytokine with diverse biological roles.
• The specific effects of IL-6 on pancreatic beta-cells require further elucidation.
• Interleukin-1 beta (IL-1) is known to negatively impact beta-cell function.

Purpose of the Study:

• To investigate the direct in vitro effects of IL-6 on pancreatic beta-cells.
• To compare the effects of recombinant human IL-6 (rIL-6) and natural human IL-6 (nIL-6).
• To examine the potential interaction between IL-6 and IL-1 beta in regulating beta-cell function.

Main Methods:

• Isolated Lewis rat islets were cultured and incubated with varying concentrations of rIL-6 or nIL-6.
• Insulin secretion and intra-islet insulin content were measured over six days.
• Electron microscopy was used to assess ultrastructural changes in beta-cells.
• Islets were also co-cultured with rIL-6 and rIL-1 beta to study protective effects.

Main Results:

• Both rIL-6 and nIL-6 significantly stimulated insulin secretion (P < 0.01) without altering intra-islet insulin levels.
• rIL-6 dose-dependently increased insulin in supernatants, doubling it at concentrations above 1.5 ng/ml.
• rIL-6 (0.5 ng/ml) preserved insulin secretion when islets were co-cultured with inhibitory concentrations of rIL-1 beta.
• Ultrastructural analysis revealed IL-6 induced beta-cell specific degenerative changes, including opaque intracytoplasmic bodies, autophagic vacuoles, and mitochondrial damage, similar to IL-1 beta.

Conclusions:

• Human IL-6 stimulates both insulin production and secretion in vitro.
• IL-6 induces ultrastructural changes in pancreatic beta-cells comparable to those caused by IL-1 beta.
• IL-6 may act as an endogenous mediator for some of the beta-cell effects attributed to IL-1.