Low-level red laser therapy alters effects of ultraviolet C radiation on Escherichia coli cells.
ACTA ACUST UNITED AC 2015;
48:939-44. [PMID:
26445338 PMCID:
PMC4617121 DOI:
10.1590/1414-431x20154459]
[Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Accepted: 04/23/2015] [Indexed: 11/29/2022]
Abstract
Low-level lasers are used at low power densities and doses according to clinical
protocols supplied with laser devices or based on professional practice. Although use
of these lasers is increasing in many countries, the molecular mechanisms involved in
effects of low-level lasers, mainly on DNA, are controversial. In this study, we
evaluated the effects of low-level red lasers on survival, filamentation, and
morphology of Escherichia colicells that were exposed to ultraviolet
C (UVC) radiation. Exponential and stationary wild-type and
uvrA-deficientE. coli cells were exposed to a
low-level red laser and in sequence to UVC radiation. Bacterial survival was
evaluated to determine the laser protection factor (ratio between the number of
viable cells after exposure to the red laser and UVC and the number of viable cells
after exposure to UVC). Bacterial filaments were counted to obtain the percentage of
filamentation. Area-perimeter ratios were calculated for evaluation of cellular
morphology. Experiments were carried out in duplicate and the results are reported as
the means of three independent assays. Pre-exposure to a red laser protected
wild-type and uvrA-deficient E. coli cells against
the lethal effect of UVC radiation, and increased the percentage of filamentation and
the area-perimeter ratio, depending on UVC fluence and physiological conditions in
the cells. Therapeutic, low-level red laser radiation can induce DNA lesions at a
sub-lethal level. Consequences to cells and tissues should be considered when
clinical protocols based on this laser are carried out.
Collapse