Aging is thought to be associated with a higher susceptibility to renal ischemia-reperfusion injury (IRI). To study whether defective induction of hemeoxygenase-1 (HO-1, a protective and anti-inflammatory enzyme) might contribute to this, we found that while 12-month-old mice had similar baseline renal function and HO-1 expression, the induction of HO-1 usually seen in ischemia-reperfusion was reduced. This was also associated with worsened renal function and acute tubular necrosis in the aged compared with young mice. In the older mice, heme arginate (HA) induced HO-1 in the cortex and medulla, significantly improved renal function, and reduced tissue injury. Cellular HO-1 induction in the medulla in response to injury or HA treatment was found to be interstitial rather than epithelial, as evidenced by its colocalization with macrophage markers. In vitro, HA treatment of primary macrophages resulted in marked HO-1 induction without impairment of classical activation pathways. Macrophage depletion, caused by diphtheria toxin treatment of 12-month-old CD11b-DTR transgenic animals, resulted in the loss of interstitial HO-1-positive cells and reversal of the protective phenotype of HA treatment. Thus, failure of HO-1 induction following renal IRI worsens structural and functional injury in older mice and represents a therapeutic target in the elderly. Hence, HO-1-positive renal macrophages mediate HA-induced protection in IRI.

Sex ratio theory provides a clear and simple way to test if nonsocial haplodiploid wasps can discriminate between kin and nonkin. Specifically, if females can discriminate siblings from nonrelatives, then they are expected to produce a higher proportion of daughters if they mate with a sibling. This prediction arises because in haplodiploids, inbreeding (sib‐mating) causes a mother to be relatively more related to her daughters than her sons. Here we formally model this prediction for when multiple females lay eggs in a patch, and test it with the parasitoid wasp Nasonia vitripennis. Our results show that females do not adjust their sex ratio behaviour dependent upon whether they mate with a sibling or nonrelative, in response to either direct genetic or a range of indirect environmental cues. This suggests that females of N. vitripennis cannot discriminate between kin and nonkin. The implications of our results for the understanding of sex ratio and social evolution are discussed.

Amelioration of rodent type 2 diabetes by hemin has been linked to increased heme oxygenase (HO) activity, however alternative mechanisms have recently been proposed for its anti-diabetic effect. We sought to determine the anti-diabetic efficacy of heme arginate (HA), a clinically licensed preparation of heme, and whether its predominant mode of action is via increased HO activity. Intravenous administration of HA reduced hyperglycemia in diabetic (db/db) mice. Co-administration of the HO inhibitor stannous (IV) mesoporphyrin IX dichloride (SM) resulted unexpectedly in a further improvement in glycaemic control despite restoring HO activity to baseline levels. The anti-diabetic effects of HA±SM were associated with increased adiposity, increased serum adiponectin levels, reduced adipose tissue and islet inflammation and preservation of islet β-cell function. HO activity independent effects of HA on adipogenesis and β-cell inflammation were further confirmed in cell culture models using the 3T3-L1 pre-adipocyte and MIN6 β-cell lines, respectively. In conclusion, our work demonstrates that the heme component of HA ameliorates experimental type 2 diabetes by promoting metabolically favourable adipogenesis and preserving islet β-cell function, but this is not mediated via increased HO activity.