Regulation of Neurite Outgrowth by Intermittent Irradiation of Visible Light

Abstract

The effect of neurite outgrowth of PC12 cells on collagen-coated glass plates under intermittent light irradiation at 525 nm and 0.4 mW/cm2 of intensity was investigated. Neurite outgrowth of PC12 cells was significantly suppressed when PC12 cells were cultivated under intermittent light irradiation with a total irradiation time of more than 2 min/h. No temperature increase was observed in the culture medium under either continuous or intermittent light irradiation. Therefore, suppression of neurite outgrowth under light irradiation was not due to the increase of temperature in the culture medium, but rather the effect of light on the PC12 cells, especially the signal transmittance of light to PC12 cells. The light irradiation interval also affected the neurite outgrowth of PC12 cells when the total irradiation time was constant. A high extension ratio of neurite outgrowth was observed under a long time interval of nonirradiation between light irradiations (1 min of irradiation every hour) as compared with frequent light irradiation intervals (5 s of irradiation every 5 min) with the same total irradiation period per hour. The neurite outgrowth ratio was thought to be dependent on the light intensity, the total time of light irradiation in the intermittent light irradiation, and the interval of light irradiation in the intermittent light irradiation.

Analysis of laser-induced heating in optical neuronal guidance

“…Previous estimates of this effect in the optical neuronal guidance experiments suggested a negligible temperature increase (Albrecht-Buehler, 1991;Carnegie et al, 2008Carnegie et al, , 2009Ehrlicher et al, 2002;Graves et al, 2009;Higuchi et al, 2005Higuchi et al, , 2007Mohanty et al, 2005;Stevenson et al, 2006;Mathew et al, 2010;Koch et al, 2004), but our more detailed simulations show a temperature increase of the order 1 • C/100 mW of laser power, which is in agreement with experimental results and modelling from the field of optical trapping (Schönle and Hell, 1998;Braun and Libchaber, 2002;Peterman et al, 2003;Ebert et al, 2007). Furthermore, we find a temperature gradient of the order 1 • C/typical neuronal growth cone-radius.…”

“…A curious new addition to the field of neuronal guidance is optical neuronal guidance (Carnegie et al, 2008(Carnegie et al, , 2009Ehrlicher et al, 2002;Graves et al, 2009;Higuchi et al, 2005Higuchi et al, , 2007Mohanty et al, 2005;Stevenson et al, 2006;Mathew et al, 2010;Koch et al, 2004) reviewed in Franze and Guck (2010) and Stevenson et al (2010). In 1991 it was first observed that Swiss 3T3 cells (mammalian fibroblast-like cells) would extend pseudopodia towards near-infrared light sources (Albrecht-Buehler, 1991), and in 2002 it was shown that a near-infrared laser spot placed on and in front of the leading edge of growing PC12 and NG108 neurons enhanced the neuronal growth into the laser spot and resulted in laser-guided turns of the growth cone and increased growth speed (Ehrlicher et al, 2002).…”

Visible light regulates neurite outgrowth of nerve cells

“…Only suppression of neurite outgrowth was reported in our previous study (Higuchi et al 2003(Higuchi et al , 2005. Here, we report the effect of different wavelengths (i.e., 455, 470, 525, 600, 630, 880 and 945 nm) of light emiting diode (LED) light on neurite outgrowth of PC12 cells.…”

“…Cell line and cultures PC12 cells (Riken Cell Bank, Ibaraki, Japan) were maintained at 37°C in RPMI1640 medium (JRH Bioscience, Lenexa, KS) supplemented with 5% heat-inactivated horse serum (JRH Biosciences, Lenexa, KS, USA), 10% fetal calf serum (JRH Biosciences, Lenexa, KS, USA), 100 U/mL penicillin and 100 lg/mL streptomycin (Oberdoerster and Rabin 1999;Hara et al 2000;Higuchi et al 2003Higuchi et al , 2005.…”

“…In our previous study, we found that neurite outgrowth of nerve-like PC12 cells in polystyrene tissue culture flasks and collagen-coated glass plates was suppressed by visible light irradiation from the lamp of an inverted light microscope (Higuchi et al 2003(Higuchi et al , 2005. In those studies, PC12 cells were irradiated with light of wavelength $525 nm and greater than 800 nm through three filters (frost filter, daylight balancing filter and green interference filter) continuously or intermittently.…”