Handbook of Vitamin C Research

Prefacexvdetoxification defence system to cope with radicals, including formation of water-solubleantioxidant, such as vitamin C. The most significant findings and conclusions of the presentstudy are as follows: (a) Vitamin C is a good bioindicator of oxidative stress and an earlywarningtool to detect changes in the metabolism of spruce needles, although the authorsfound untypical reaction of antioxidant defence in the case of extremely high SO 2 exposure.(b) Metabolic processes in spruce needles react to air pollution according to severity ofpollution and the time of exposure. However, if spruce trees were exposed to high SO 2ambient levels and/or for a long period of time, the antioxidant defence mechanism would bedamaged and the content of vitamin C would not increase as expected. (c) Lower exposure toambient pollution results in better vitality of trees (e.g., higher contents of total (a + b)chlorophyll), as well as in rising of their defence capabilities (higher contents of vitamin C).(d) Physiological condition of Norway spruce in northern Slovenia has significantlyimproved since 1995, when the desulphurization devices were built on the ŠTPP, and whenemissions of SO 2 as well as heavy metals started dramatically and continuously decreasing inthis part of Slovenia.Chapter XIII - Different heavy metals, such as lead and mercury, are potential chemicalcontaminants contained in air, water and foods, particularly fish. Several studies havereported that these toxic metals may affect the vascular system. Chronic exposure to mercuryand lead has been associated with numerous cardiovascular disorders such as hypertension,endothelial dysfunction and nephrotoxicity. Most of the deleterious effects of mercury andlead on the vascular wall have been attributed to their pro-oxidant properties. Vitamin C, dueto its antioxidant properties, may play a protective role in the vascular damage induced bychronic exposure to mercury and lead. It has been described that vitamin C administrationprevents the increase of mean arterial blood pressure, restoring the normal expression ofendothelial nitric oxide synthase and soluble guanylate cyclase proteins in the vascular wallof lead-exposed rats. This protective role of vitamin C in endothelial functionality suggeststhat vitamin C supplementation may be beneficial for subjects submitted to chronic heavymetal exposure. This chapter will focus on analyzing the mechanisms of vascular damageinduced by mercury and lead and the protective effect of vitamin C on molecular pathwaysinvolved in the vascular damage related to their chronic exposure.Chapter XIV - Endothelial dysfunction (ED) plays a critical role in the development ofcardiovascular complications preceding by decades their onset. Reversal of ED has beenpostulated to prevent atherosclerosis and several attempts have been done in this direction.Vitamin C has been suggested to reverse ED by several mechanisms: it serves as a potentantioxidant; it directly enhances the activity of nitric oxide synthase; the acyl CoA oxidasesystem and counteracts the action of proinflammatory lipids. Multiple data from experimentaland clinical studies have proven protective effects of vitamin C on endothelium. Though, thetherapeutic indication is limited by the low biodisponibility following oral ascorbateadministration and a rapid clearance. While oral, prophylactic approaches of treatment withvitamin C are difficult to implement, a large body of evidence proves the beneficial effects ofparenteral administration in critically ill patients. Supraphysiologic levels of ascorbate mayfacilitate the restoration of vascular function in patients after severe burns and other majortraumas. This translates clinically into reduced circulatory shock, fluid requirements andoedema. The effects on the microcirculation seem to be of particular interest since