84 The inhibition of prostaglandin biosynthesis by human haptoglobin and its relationship with haemoglobin binding

Haptoglobin dampens endotoxin‐induced inflammatory effects both in vitro and in vivo

“…However, IL‐10 production was markedly suppressed by Hp. PGE 2 release was not measured but it is unlikely that it could contribute to the observed effects because Hp is known to inhibit prostaglandin synthase and PGE 2 synthesis 13,18 , 24,49 …”

“…However, some of them exhibit a variety of immunomodulatory effects 13–19 . Among those, haptoglobin (Hp) has been reported to be a potent anti‐inflammatory agent 18,20–25 . Hp has been shown to inhibit the respiratory burst and rise in intracellular calcium in neutrophils following their stimulation with N ‐formyl‐methionyl‐leucyl‐phenylalanine 15 .…”

Haptoglobin and the development of cerebral artery vasospasm after subarachnoid hemorrhage

“…In general, haptoglobin containing the ␣2 gene product does not inhibit hemoglobin's effects on free radical production and prostaglandin levels as well as does haptoglobin ␣1-␣1. [14][15][16]18,26,27 Furthermore, haptoglobin ␣2-␣2 may worsen the local inflammatory response in the subarachnoid space after SAH, as is suggested by the recent observations that the complex of hemoglobin with haptoglobin ␣2-␣2 is 1) more potent than that with haptoglobin ␣1-␣1 at activating the monocyte/macrophage CD163 receptor 18 and 2) less able to stimulate production of anti-inflammatory cytokines from cultured monocytes (A. Levy, PhD, unpublished data, 2005).…”

“…The binding of haptoglobin to hemoglobin interferes with the ability of hemoglobin to induce free radical production and alter prostaglandin levels. [14][15][16] Haptoglobin also facilitates the uptake and degradation of the hemoglobin by reticuloendothelial cells. 17,18 Because of its antihemoglobin activity and its presence in the subarachnoid space after SAH, 19 haptoglobin likely neutralizes extracorpuscular hemoglobin as the hemoglobin is released from the decaying red blood cells.…”

Human serum haptoglobin is toxic to Plasmodium falciparum in vitro

“…In recent years haptoglobin has been found to have various other functions, e.g. inhibition of prostaglandin synthesis [5], promotion of angiogenesis [6], antibody-like agglutination of Streptococcus pyogenes strains carrying the membrane antigen, T4 [7], inhibition of lectin-induced lymphocyte transformation, mediated by binding to 2 CD22 [8], promoting Thl-dominant T cell responses, possibly mediated via CDllb [9] and inhibition of the respiratory burst by phagocytes, mediated via CDllb [10].…”