Paper detail

Raman spectroscopic detection of rapid, reversible, early-stage inflammatory cytokine-induced apoptosis of adult hippocampal progenitors/stem cells

The role of neuro-inflammation in diverse, acute and chronic brain pathologies is being increasingly recognized. Neuro-inflammation is accompanied by increased levels of both pro- and anti-inflammatory cytokines; these have deleterious as well as protective/reparative effects. Inflammation has varying effects on neurogenesis and is a subject of intense contemporary interest. We show that TNF-alpha and IFN-gamma, used concomitantly, cause apoptosis of adult rat hippocampal progenitor/stem cells in vitro as detected by the TUNEL and MTT assays on time scales of several hours. We have coupled Raman spectroscopy to an optical trap to probe early changes of apoptosis in single, live neural stem cells that have been treated with pro-inflammatory cytokines, TNF-alpha and IFN-gamma. Changes caused by inflammation-induced denaturation of DNA are observed in the Raman spectra that correspond to very early stages of apoptosis, occurring on very fast time scales: as short as 10 minutes. Addition of the anti-inflammatory cytokine IL-10 either 10-30 min before or 10-30 min after treatment with TNF-alpha and IFN-gamma reverses the changes substantially. Our findings imply that inflammation can induce very rapid changes leading to cell death but that these are reversible, in the early stages at least.