Nicotinamide Phosphoribosyltransferase Upregulation by Phenylephrine Reduces Radiation Injury in Submandibular Gland.
Radiation therapy for head and neck cancer commonly leads to radiation sialadenitis. Emerging evidence has indicated that phenylephrine pretreatment reduces radiosensitivity in the salivary gland; however, the underlying cytoprotective mechanism remains unclear. Nicotinamide phosphoribosyltransferase (NAMPT) is not only a key enzyme for the nicotinamide adenine dinucleotide salvage pathway, but also a cytokine participating in cell survival, metabolism, and longevity, with a broad effect on cellular functions in physiology and pathology. However, the regulatory events of NAMPT in response to the irradiated salivary gland are unknown.



The cell viability of primary cultured submandibular gland cells was determined using the PrestoBlue assay. NAMPT expression was measured using reverse transcriptase polymerase chain reaction and Western blotting in vitro and in vivo. Silent information regulator 1 (SIRT1) and phosphorylated Akt protein levels were examined by Western blotting. The cellular locations of NAMPT and SIRT1 were detected by immunohistochemistry. NAMPT promoter activity was assessed using the luciferase reporter gene assay.



NAMPT was mainly distributed in the cytoplasm of granular convoluted tubule cells and ductal cells in normal submandibular glands. mRNA and protein expression of NAMPT was downregulated after radiation but upregulated with phenylephrine pretreatment both in vivo and in vitro. Moreover, the protein expression of phosphorylated Akt and SIRT1 was decreased in irradiated glands, and phenylephrine pretreatment restored the expression of both. SIRT1 was mainly located in the cell nucleus and cytoplasm in the normal submandibular gland. Phenylephrine dramatically enhanced the expression of SIRT1, which was significantly reduced by radiation. Furthermore, phenylephrine induced a marked increase of NAMPT promoter activity.



These findings reveal the regulatory mechanisms of NAMPT expression, which help to understand the mechanism of the cytoprotective role of phenylephrine on irradiated tissues.
Laboratory of Oral and Maxillofacial Disease, Second Hospital of Dalian Medical University, Dalian, China. Electronic address: xiangbin72@163.com.
Bin
B
Xiang
Department of Oral Medicine and Medical Research Center of Medical College, Dalian University, Dalian, China.
Lichi
L
Han
Laboratory of Oral and Maxillofacial Disease, Second Hospital of Dalian Medical University, Dalian, China.
Xinyue
X
Wang
Life Sciences and Technology College, Dalian University, Dalian, China.
Ling
L
Tang
Department of Oral and Maxillofacial Surgery, Second Hospital of Dalian Medical University, Dalian, China.
Kailiang
K
Li
Department of Oral Medicine and Medical Research Center of Medical College, Dalian University, Dalian, China.
Xiuxiu
X
Li
Department of Oral and Maxillofacial Surgery, Second Hospital of Dalian Medical University, Dalian, China.
Xibo
X
Zhao
Department of Oral Medicine and Medical Research Center of Medical College, Dalian University, Dalian, China.
Miaomiao
M
Xia
Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, New Mexico.
Xixi
X
Zhou
Department of Oral and Maxillofacial Surgery, Second Hospital of Dalian Medical University, Dalian, China.
Fuyin
F
Zhang
Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, New Mexico. Electronic address: kliu@salud.unm.edu.
Ke Jian
KJ
Liu
D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D005260:Female; D008297:Male; D054409:Nicotinamide Phosphoribosyltransferase / Q000096:biosynthesis*; D010656:Phenylephrine / Q000008:administration & dosage*; D011829:Radiation Dosage; D011837:Radiation-Protective Agents / Q000008:administration & dosage*; D051381:Rats; D017208:Rats, Wistar; D013363:Submandibular Gland / Q000187:drug effects / Q000201:enzymology / Q000503:physiopathology* / Q000528:radiation effects*; D016896:Treatment Outcome; D015854:Up-Regulation / Q000187:drug effects
D011837:Radiation-Protective Agents; D010656:Phenylephrine; D054409:Nicotinamide Phosphoribosyltransferase