Evidence Suggesting a Role of Iron in a Mouse Model of Nephrogenic Systemic Fibrosis

Nephrogenic systemic fibrosis is associated with gadolinium contrast exposure in patients with reduced kidney function and carries high morbidity and mortality. We have previously demonstrated that gadolinium contrast agents induce in vivo systemic iron mobilization and in vitro differentiation of peripheral blood mononuclear cells into ferroportin (iron exporter)-expressing fibrocytic cells. In the present study we examined the role of iron in a mouse model of nephrogenic systemic fibrosis. Chronic kidney disease was induced in 8-week-old male Balb/C mice with a two-step 5/6 nephrectomy surgery. Five groups of mice were studied: control (n = 5), sham surgery control (n = 5), chronic kidney disease control (n = 4), chronic kidney disease injected with 0.5 mmol/kg body weight of Omniscan 3 days per week, for a total of 10 injections (n = 8), and chronic kidney disease with Omniscan plus deferiprone, 125 mg/kg, in drinking water (n = 9). Deferiprone was continued for 16 weeks until the end of the experiment. Mice with chronic kidney disease injected with Omniscan developed skin changes characteristic of nephrogenic systemic fibrosis including hair loss, reddening, ulceration, and skin tightening by 10 to 16 weeks. Histopathological sections demonstrated dermal fibrosis with increased skin thickness (0.25±0.06 mm, sham; 0.34±+0.3 mm, Omniscan-injected). Additionally, we observed an increase in tissue infiltration of ferroportin-expressing, fibrocyte-like cells accompanied by tissue iron accumulation in the skin of the Omniscan-treated mice. The deferiprone-treated group had significantly decreased skin thickness (p<0.05) and significantly decreased dermal fibrosis compared to the Omniscan-only group. In addition, iron chelation prevented tissue infiltration of ferroportin-expressing, fibrocyte-like cells. Our in vitro experiments demonstrated that exposure to Omniscan resulted in the release of catalytic iron and this was prevented by the iron chelator deferiprone. Deferiprone inhibited the differentiation of human peripheral blood mononuclear cells into ferroportin-expressing cells by immunohistochemical staining and western blot analysis. Our studies support an important role of iron in the pathophysiology of gadolinium chelate toxicity and nephrogenic systemic fibrosis.     

NAD metabolism in aging and cancer

NAD⁺ and its derivatives NADH, NADP⁺, and NADPH are essential cofactors in redox reactions and electron transport pathways. NAD serves also as substrate for an extensive series of regulatory enzymes including cyclic ADP-ribose hydrolases, mono(ADP-ribosyl)transferases, poly(ADP-ribose) polymerases, and sirtuin deacetylases which are O-acetyl-ADP-ribosyltransferases. As a result of the numerous and diverse enzymes that utilize NAD as well as depend on its synthesis and concentration, significant interest has developed in its role in a variety of physiologic and pathologic processes, and therapeutic initiatives have focused both on augmenting its levels as well as inhibiting some of its pathways. In this article, we examine the biosynthesis of NAD, metabolic processes in which it is involved, and its role in aging, cancer, and other age-associated comorbidities including neurodegenerative, cardiovascular, and metabolic disorders. Therapeutic interventions to augment and/or inhibit these processes are also discussed.Impact statementNAD is a central metabolite connecting energy balance and organismal growth with genomic integrity and function. It is involved in the development of malignancy and has a regulatory role in the aging process. These processes are mediated by a diverse series of enzymes whose common focus is either NAD’s biosynthesis or its utilization as a redox cofactor or enzyme substrate. These enzymes include dehydrogenases, cyclic ADP-ribose hydrolases, mono(ADP-ribosyl)transferases, poly(ADP-ribose) polymerases, and sirtuin deacetylases. This article describes the manifold pathways that comprise NAD metabolism and promotes an increased awareness of how perturbations in these systems may be important in disease prevention and/or progression.     

Relationship between CD4 T cell turnover,cellular differentiation and HIV persistence during ART

The precise role of CD4 T cell turnover in maintaining HIV persistence during antiretroviral therapy (ART) has not yet been well characterized. In resting CD4 T cell subpopulations from 24 HIV-infected ART-suppressed and 6 HIV-uninfected individuals, we directly measured cellular turnover by heavy water labeling, HIV reservoir size by integrated HIV-DNA (intDNA) and cell-associated HIV-RNA (caRNA), and HIV reservoir clonality by proviral integration site sequencing. Compared to HIV-negatives, ART-suppressed individuals had similar fractional replacement rates in all subpopulations, but lower absolute proliferation rates of all subpopulations other than effector memory (TEM) cells, and lower plasma IL-7 levels (p = 0.0004). Median CD4 T cell half-lives decreased with cell differentiation from naïve to TEM cells (3 years to 3 months, p<0.001). TEM had the fastest replacement rates, were most highly enriched for intDNA and caRNA, and contained the most clonal proviral expansion. Clonal proviruses detected in less mature subpopulations were more expanded in TEM, suggesting that they were maintained through cell differentiation. Earlier ART initiation was associated with lower levels of intDNA, caRNA and fractional replacement rates. In conclusion, circulating integrated HIV proviruses appear to be maintained both by slow turnover of immature CD4 subpopulations, and by clonal expansion as well as cell differentiation into effector cells with faster replacement rates.     

Skeletal muscle carnitine metabolism in patients with unilateral peripheral arterial disease.

Patients with peripheral arterial disease (PAD) have abnormalities of carnitine metabolism that may contribute to their functional impairment. To test the hypothesis that muscle acylcarnitine generation (intermediates in oxidative metabolism) in patients with PAD provides a marker of the muscle dysfunction, 10 patients with unilateral PAD and 6 age-matched control subjects were studied at rest, and the patients were studied during exercise. At rest, biopsies of the gastrocnemius muscle in the patients' nonsymptomatic leg revealed a normal carnitine pool and lactate content compared with control subjects. In contrast, the patients' diseased leg had higher contents of lactate and long-chain acylcarnitines than controls. The muscle short-chain acylcarnitine content in the patients' diseased leg at rest was inversely correlated with peak exercise performance (r = -0.75, P less than 0.05). With graded treadmill exercise, only patients who exceeded their individual lactate threshold had an increase in muscle short-chain acylcarnitine content in the nonsymptomatic leg, which was identical to the muscle carnitine response in normal subjects. In the patients' diseased leg, muscle short-chain acylcarnitine content increased with exercise from 440 +/- 130 to 900 +/- 200 (SE) nmol/g (P less than 0.05). In contrast to the nonsymptomatic leg, there was no increase in muscle lactate content in the diseased leg with exercise, and the change in muscle carnitine metabolism was correlated with exercise duration (r = 0.82, P less than 0.01) and not with the lactate threshold. We conclude that energy metabolism in ischemic muscle of patients with PAD is characterized by the accumulation of acylcarnitines.(ABSTRACT TRUNCATED AT 250 WORDS)