Induction of hypoxia-inducible factor-1alpha and activation of caspase-3 in hypoxia-reoxygenated bone marrow stroma is negatively regulated by the delayed production of substance P.
The bone marrow (BM), which is the major site of immune cell development in the adult, responds to different stimuli such as inflammation and hemorrhagic shock. Substance P (SP) is the major peptide encoded by the immune/hemopoietic modulator gene, preprotachykinin-1 (PPT-I). Differential gene expression using a microarray showed that SP reduced hypoxia-inducible factor-1alpha (HIF-1alpha) mRNA levels in BM stroma. Because long-term hypoxia induced the expression of PPT-I in BM mononuclear cells, we used timeline studies to determine whether PPT-I is central to the biologic responses of BM stroma subjected to 30-min hypoxia (pO(2) = 35 mm Hg) followed by reoxygenation. HIF-1alpha mRNA and protein levels were increased up to 12 h. At this time, beta-PPT-I mRNA was detected with the release of SP at 16 h. SP release correlated with down-regulation of HIF-1alpha to baseline. A direct role for SP in HIF-1alpha expression was demonstrated as follows: 1) transient knockout of beta-PPT-I showed an increase in HIF-1alpha expression up to 48 h of reoxygenation; and 2) HIF-1alpha expression remained baseline during reoxygenation when stroma was subjected to hypoxia in the presence of SP. Reoxygenation activated the PPT-I promoter with concomitant nuclear translocation of HIF-1alpha that can bind to the respective consensus sequences within the PPT-I promoter. SP reversed active caspase-3, an indicator of apoptosis and erythropoiesis, to homeostasis level after reoxygenation of hypoxic stroma. The results show that during reoxgenation the PPT-I gene acts as a negative regulator on the expression of HIF-1alpha and active caspase-3 in BM stroma subjected to reoxygenation.
Qian
J
J
Department of Medicine, Trauma Division, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103, USA.
Ramroop
K
K
McLeod
A
A
Bandari
P
P
Livingston
D H
DH
Harrison
J S
JS
Rameshwar
P
P
D020121:5' Untranslated Regions; D000328:Adult; D001853:Bone Marrow / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D015687:Cell Hypoxia; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D006410:Hematopoiesis; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D010100:Oxygen / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D011498:Protein Precursors / Q000235:genetics; D017154:Stromal Cells / Q000378:metabolism; D013373:Substance P / Q000096:biosynthesis*; D015320:Tachykinins / Q000235:genetics; D014157:Transcription Factors / Q000096:biosynthesis*
D020121:5' Untranslated Regions; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D011498:Protein Precursors; D015320:Tachykinins; D014157:Transcription Factors; C044206:preprotachykinin; D013373:Substance P; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D010100:Oxygen