Photodynamic therapy with rose bengal induces GroEL expression in Streptococcus mutans.
Heat-shock proteins (HSPs) are indicative of stressing conditions that may affect cell viability. In Streptococcus mutans, acid stress induces high levels of GroEL, an HSP, in addition to metabolic alterations, as shown by proteomic analysis.


OBJECTIVE
We tested whether the expression of GroEL by S. mutans was enhanced after photodynamic therapy (PDT) with rose bengal.


METHODS
S. mutans was grown in complete medium supplemented with 50 mmol/L glucose. The test conditions used were as follows: Rose bengal (0.1 micromol/L) with and without light treatment (500 mJ/cm(2)), light treatment alone, and 1 mol/L NaCl (as a stress condition). The extracellular pH of bacteria was monitored; HSP expression was assayed with Western blot, and possible DNA damage analyzed.


RESULTS
Higher HSP expression was detected in bacteria after PDT treatment as compared with light or dye alone (negative controls). The expression of HSP after PDT was similar to that induced by osmotic stress. No DNA degradation was observed after PDT of S. mutans.


CONCLUSIONS
PDT may cause effects similar to those of other stressing conditions in S. mutans, and cell death induced by this treatment reflects its incapacity to protect itself sufficiently against the deleterious effects of PDT with Rose bengal.
Bolean
Mayte
M
Departamento de Química, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, FFCLRP-USP, Ribeirão Preto, SP, Brasil.
Paulino
Tony de Paiva
Tde P
Thedei
Geraldo
G
Ciancaglini
Pietro
P
D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D018834:Chaperonin 60 / Q000378:metabolism*; D004249:DNA Damage; D005456:Fluorescent Dyes; D010778:Photochemotherapy; D017319:Photosensitizing Agents; D012395:Rose Bengal / Q000627:therapeutic use*; D013295:Streptococcus mutans / Q000187:drug effects / Q000528:radiation effects*
D018834:Chaperonin 60; D005456:Fluorescent Dyes; D017319:Photosensitizing Agents; D012395:Rose Bengal