Neopterin has been extensively used as a clinical marker of immune activation during inflammation in a wide range of conditions and stresses. However, the analysis of neopterin alone neglects the cellular reactions that generate it in response to interferon-γ. Neopterin is the oxidation product of 7,8-dihydroneopterin, which is a potent antioxidant generated by interferon-γ-activated macrophages. 7,8-Dihydroneopterin can protect macrophage cells from a range of oxidants through a scavenging reaction that generates either neopterin or dihydroxanthopterin, depending on the oxidant. Therefore, plasma and urinary neopterin levels are dependent on both macrophage activation to generate 7,8-dihydroneopterin and subsequent oxidation to neopterin. This relationship is clearly shown in studies of exercise and impact-induced injury during intense contact sport. Here, we argue that neopterin and total neopterin, which is the combined value of 7,8-dihydroneopterin and neopterin, could provide a more comprehensive analysis of clinical inflammation than neopterin alone.

Rugby union is a sport governed by the impacts of high force and high frequency. Analysis of physiological markers following a game can provide an understanding of the physiological response of an individual and the time course changes in response to recovery. Urine and saliva were collected from 11 elite amateur rugby players 24 h before, immediately after, and at 17, 25, 38, 62 and 86 h post-game. Myoglobin, salivary immunoglobulin A and cortisol were analysed by ELISA, whereas neopterin and total neopterin were analysed by high-performance liquid chromatography. There was a significant post-game increase of all four markers. The increases were cortisol 4-fold, myoglobin 2.85-fold, neopterin 1.75-fold and total neopterin 2.3-fold when corrected with specific gravity. All significant changes occurred post-game only, with markers returning to and remaining at baseline within 17 h. The intensity of the game caused significant changes in key physiological markers of stress. They provide an understanding of the stress experienced during a single game of rugby and the time course changes associated with player recovery. Neopterin provides a new marker of detecting an acute inflammatory response in physical exercise, while specific gravity should be considered for urine volume correction post-exercise.

The rise in plasma neopterin observed with increasing severity of vascular disease is a strong indicator of the inflammatory nature of atherosclerosis. Plasma neopterin originates as the oxidation product of 7,8‐dihydroneopterin secreted by γ ‐interferon stimulated macrophages within atherosclerotic plaques. Neopterin is increasingly being used as a marker of inflammation during clinical management of patients with a range of disorders including atherosclerosis. Yet the role of 7,8‐dihydroneopterin/neopterin synthesis during the inflammatory process and plaque formation remains poorly understood and controversial. This is partially due to the unresolved role oxidants play in atherosclerosis and the opposing roles of 7,8‐dihydroneopterin/neopterin. Neopterin can act as pro‐oxidant, enhancing oxidant damage and triggering apoptosis in a number of different cell types. Neopterin appears to have some cellular signalling properties as well as being able to chelate and enhance the reactivity of transition metal ions during Fenton reactions. In contrast, 7,8‐dihydroneopterin is also a radical scavenger, reacting with and neutralizing a range of reactive oxygen species including hypochlorite, nitric oxide and peroxyl radicals, thus protecting lipoproteins and various cell types including macrophages. This has led to the suggestion that 7,8‐dihydroneopterin is synthesized to protect macrophages from the oxidants released during inflammation. The oxidant/antioxidant activity observed in vitro appears to be determined both by the relative concentration of these compounds and the specific chemistry of the in vitro system under study. How these activities might influence or modulate the development of atherosclerotic plaque in vivo will be explored in this review. British Journal of Pharmacology (2008) 153 , 627–635; doi: 10.1038/sj.bjp.0707408 ; published online 13 August 2007

Body building is a sport where ultrastructual damage to muscle fibres aids the development of dense muscle layers. Using a new strong cation exchange (SCX) based chromatography technique to measure neopterin and 7,8-dihydroneopterin, we investigated whether this muscle damage caused increased levels of inflammation. Urine samples were collected over eight consecutive mornings from 10 natural competitive body builders. Samples were analysed using SCX high performance liquid chromatography (HPLC) with urine volume corrected for creatinine and specific gravity (SG). The majority of subjects showed large changes in both neopterin and total neopterin (7,8-dihydroneopterin+neopterin) levels, though the mean data for the group showed no significant change over the week. There was no evidence of the high intensity resistance training causing an accumulation of inflammation as the values for all the body builders returned to close to the starting values after 2 days rest. The SCX analysis had an intra-specific viability of 3.04% and the inter-specific viability was 5.42%. Urine volume correction with SG was found to give the same values as using creatinine. Creatinine and specific gravity are both reliable methods for correcting for urine volume while SCX HPLC provides a new means of measuring urinary neopterin and total neopterin.

Macrophage cells within inflammatory lesions are exposed to a wide range of degrading and cytotoxic molecules including reactive oxygen species. Unlike neutrophils, macrophages do not normally die in this environment but continue to generate oxidants, phagocytose cellular remains, and release a range of cyto-active agents which modulate the immune response. It is this potential of the macrophage cell to survive in an oxidative environment that allows the growth and complexity of advanced atherosclerotic plaques. This review will examine the oxidants encountered by macrophages within an atherosclerotic plaque and describe some of the potential antioxidant mechanisms which enable macrophages to function within inflammatory lesions. Ascorbate, a-tocopherol, and glutathione appear to be central to the protection of macrophages yet additional antioxidant mechanisms appear to be involved. Gamma-Interferon causes macrophages to generate 7,8-dihydroneopterin, neopterin and 3-hydroxyanthranilic acid both of which have antioxidant properties. Manganese superoxide dismutase is also upregulated in macrophages. The evidence that these antioxidants provide further protection, so allowing the macrophage cells to survive within sites of chronic inflammation such as atherosclerotic plaques, will be described.