Lysophosphatidic acid rescues human dental pulp cells from ischemia-induced apoptosis.
BACKGROUND
Dental pulp is particularly susceptible to ischemic conditions (hypoxia and serum deprived) because it is commonly exposed to trauma, inflammation, chronic caries injury, and pulpitis. We investigated the apoptotic response of human dental pulp cells (HDPCs) to varying levels of oxygen and serum to mimic different degrees of ischemia, tested whether lysophosphatidic acid (LPA) could reverse ischemia-induced apoptosis, and investigated the possible mechanisms of LPA.


METHODS
HDPCs were cultured under conditions mimicking serum deprivation and ischemia for 2 days with or without LPA at 25 μg/mL. Flow cytometry and JC-1 fluorescence were used to detect any apoptotic change. Western blotting was used to measure the expression of the apoptosis regulators B-cell lymphoma 2 (Bcl-2) and Bax, focal adhesion kinase (FAK), Src, extracellular signal-regulated kinase (ERK), and Akt.


RESULTS
Flow cytometry and JC-1 immunofluorescence showed that ischemia could induce apoptosis of HDPCs in 2 days and treatment with LPA could reduce cell death significantly. To clarify the molecular mechanisms, Western blot results showed up-regulation of both proapoptotic Bax and antiapoptotic Bcl-2 during apoptosis. LPA functioned as an antiapoptotic cytokine by activation of the phosphorylation of FAK and ERK. No statistically significant difference was found in the activation levels of p-Src or p-Akt.


CONCLUSIONS
A self-defense mechanism functioned during cell apoptosis. LPA could effectively rescue HDPCs from ischemia-induced apoptosis via regulation of Bax and Bcl-2 and the activation of phosphorylated FAK and phosphorylated ERK. LPA is a potent candidate for biological therapy of chronic pulpal inflammatory diseases.
State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.
Hongying
H
Pan
State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.
Li
L
Cheng
State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.
Hui
H
Yang
State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.
Wenling
W
Zou
State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China. Electronic address: applecrbb@gmail.com.
Ran
R
Cheng
State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, China.
Tao
T
Hu
D000293:Adolescent; D000328:Adult; D017209:Apoptosis / Q000187:drug effects*; D018929:Cell Culture Techniques; D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D060833:Cellular Microenvironment / Q000187:drug effects / Q000502:physiology; D003782:Dental Pulp / Q000098:blood supply / Q000166:cytology* / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000032:analysis / Q000187:drug effects; D051417:Focal Adhesion Kinase 1 / Q000032:analysis / Q000187:drug effects; D006801:Humans; D007511:Ischemia / Q000473:pathology / Q000503:physiopathology*; D008246:Lysophospholipids / Q000494:pharmacology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D020011:Protective Agents / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000032:analysis / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis / Q000187:drug effects; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000032:analysis / Q000187:drug effects; D055815:Young Adult; D051028:bcl-2-Associated X Protein / Q000032:analysis / Q000187:drug effects
D008246:Lysophospholipids; D020011:Protective Agents; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; D016392:Proto-Oncogene Proteins pp60(c-src); D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; C032881:lysophosphatidic acid
Apoptosis; human dental pulp cells; ischemia; lysophosphatidic acid