As a result of hemolysis, hemoglobin is found to accumulate in the kidney and is secreted in the urine. Haptoglobin captures, and combines with free plasma hemoglobin to allow hepatic recycling of heme iron and to prevent kidney damage. Haptoglobin also acts as an antioxidant, has antibacterial activity and plays a role in modulating many aspects of the acute phase response. Hemoglobin/haptoglobin complexes are rapidly cleared by the macrophage CD163 scavenger receptor expressed on the surface of liver Kupfer cells through an endocytic lysosomal degradation pathway.

1. This study demonistrated that increased Hp in serum came from the liver in response to TBI and that IL-6 is an important mediator of this induction. PMID: 23172820
2. Vaccenic acid normalizes serum haptoglobin in obese/insulin resistant JCR:LA-cp rats PMID: 22254015
3. activated glucocorticoid receptor through direct interactions with STAT3 and C/EBPbeta, participates in Hp gene upregulation as a transcriptional coactivator. PMID: 20155810
4. Haptoglobin deficiency worsens intracerebral hemorrhage whereas haptoglobin overexpression alleviates intracerebral hemorrhage-mediated brain injury. PMID: 20016097
5. Hp-mediated haemoglobin catabolism in lung cells may be an efficient mechanism to reduce oxidative damage associated with haemolysis PMID: 11865979
6. Haptoglobin gene expression regulation PMID: 11865981
7. Hp is transcriptionally modulated throughout prenatal hepatic development by fetal p53 protein. PMID: 11991649
8. upregulated in reactive astrocytes after transient forebrain ischemia in rats PMID: 12368655
9. Hp gene transcription is regulated by C/EBP alpha during normal liver development, whereas C/EBP beta is involved in the acute-phase response regulation during the later phase of differentiation and in the adult. PMID: 16172914
10. Western blotting and enzyme-linked immunosorbent assay clearly showed a markedly increased level of Hp in the urine, but not in the serum, of the PHN animals. PMID: 17616219
11. that interactions between C/EBPs and HDAC1 negatively regulate C/EBPdelta-dependent haptoglobin expression in intestinal epithelial cells. PMID: 17910034
12. lamin components of the nuclear matrix form a network of functional, dynamic protein-protein and protein-Hp-S/MAR associations with multiple partners, and underline the involvement of PARP-1 in the regulation of haptoglobin gene transcription. PMID: 19521970
13. Data concluded that haptoglobin gene up-regulation during chronic dietary restriction was regulated by different mechanisms than during the acute phase response. PMID: 19545490

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Secreted.

Peptidase S1 family

Expressed by the liver and secreted in plasma.

KEGG: rno:24464

UniGene: Rn.10950