The development of red blood cells (erythrocytes) is distinguished by high-level production of the oxygen carrier, haemoglobin A (HbA), a heterotetramer of alpha- and beta-haemoglobin subunits. HbA synthesis is coordinated to minimize the accumulation of free subunits that form cytotoxic precipitates. Molecular chaperones that regulate globin subunit stability, folding or assembly have been proposed to exist but have never been identified. Here we identify a protein stabilizing free alpha-haemoglobin by using a screen for genes induced by the essential erythroid transcription factor GATA-1 (refs 4, 5). Alpha Haemoglobin Stabilizing Protein (AHSP) is an abundant, erythroid-specific protein that forms a stable complex with free alpha-haemoglobin but not with beta-haemoglobin or haemoglobin A (alpha(2)beta(2)). Moreover, AHSP specifically protects free alpha-haemoglobin from precipitation in solution and in live cells. AHSP-gene-ablated mice exhibit reticulocytosis and abnormal erythrocyte morphology with intracellular inclusion bodies that stain positively for denatured haemoglobins. Hence, AHSP is required for normal erythropoiesis, probably acting to block the deleterious effects of free alpha-haemoglobin precipitation. Accordingly, AHSP gene dosage is predicted to modulate pathological states of alpha-haemoglobin excess, such as beta-thalassaemia.

Several reports have implicated reactive oxygen and nitrogen metabolites (RONS) in the initiation and/or progression of inflammatory bowel diseases (IBDs). We have investigated the role of three key RONS-metabolizing enzymes (inducible nitric oxide synthase [iNOS], superoxide dismutase [SOD], nicotinamide adenine dinucleotide phosphate [NADPH] oxidase) in a murine model of IBD. Mice genetically deficient (−/−) in either iNOS or the p47phox subunit of NADPH oxidase, transgenic (Tg) mice that overexpress SOD, and their respective wild-type (WT) littermates were fed dextran sulfate sodium (DSS) in drinking water for 7 days to induce colitis. In addition, the specific iNOS inhibitor 1400W was used in DSS-treated WT and p47phox−/− mice. WT mice responded to DSS feeding with progressive weight loss, bloody stools, elevated serum NOX and colonic mucosal injury with neutrophil infiltration. Both the onset and severity of colitis were significantly attenuated in iNOS−/− and 1400W-treated WT mice. While the responses to DSS did not differ between WT and p47phox−/− mice, enhanced protection was noted in 1400W-treated p47phox−/− mice. Interestingly, SODTg mice exhibited more severe colitis than their WT littermates. These findings reveal divergent roles for superoxide and iNOS-derived NO in intestinal inflammation.

Background Platelet activation at sites of vascular injury is essential for hemostasis, but it is also a major pathomechanism underlying ischemic injury. As anti-inflammatory therapies limit thrombosis and anti-thrombotic therapies reduce vascular inflammation, we tested the therapeutic potential of two pro-resolving endogenous mediators: Annexin A1 N-terminal derived peptide (AnxA1Ac2–26) and aspirin (ASA) triggered lipoxin A4 (ATL, 15-epi-lipoxin A4), on the cerebral microcirculation following ischemia-reperfusion (I/R) injury. Furthermore, we tested whether the lipoxin A4 receptor, formyl-peptide receptor 2/3 (Fpr2/3, ortholog to human FPR2/ALX), evoked neuro-protective functions following cerebral I/R injury. Methods and Results Using intravital microscopy, we found that cerebral I/R injury was accompanied by neutrophil and platelet activation and neutrophil-platelet aggregate (NPA) formation within cerebral microvessels. Moreover, ATL activation of neutrophil Fpr2/3 regulated NPA formation in the brain, and inhibited the reactivity of the cerebral microvasculature. The same results were obtained with AnxA1Ac2–26 administration. Blocking Fpr2/ALX with the antagonist Boc2 reversed this effect, and treatments were ineffective in Fpr2/3 knockout mice, who displayed an exacerbated disease severity, evidenced by increased infarct area, blood brain barrier dysfunction, increased neurological score and elevated levels of cytokines. Furthermore, ASA treatment significantly reduced cerebral leukocyte recruitment, and increased endogenous levels of ATL, effects again mediated by Fpr2/3. Conclusions In summary, Fpr2/ALX is a therapeutic target for initiating endogenous pro-resolving, anti-inflammatory pathways following cerebral I/R injury.