L-Arginine effects on blood pressure and renal function of intrauterine restricted rats

Amino Acids during Pregnancy and Offspring Cardiovascular-Kidney-Metabolic Health

Amino acids are essential for normal pregnancy and fetal development. Disruptions in maternal amino acid metabolism have been associated with various adult diseases later in life, a phenomenon referred to as the developmental origins of health and disease (DOHaD). In this review, we examine the recent evidence highlighting the significant impact of amino acids on fetal programming, their influence on the modulation of gut microbiota, and their repercussions on offspring outcomes, particularly in the context of cardiovascular-kidney-metabolic (CKM) syndrome. Furthermore, we delve into experimental studies that have unveiled the protective effects of therapies targeting amino acids. These interventions have demonstrated the potential to reprogram traits associated with CKM in offspring. The discussion encompasses the challenges of translating the findings from animal studies to clinical applications, emphasizing the complexity of this process. Additionally, we propose potential solutions to overcome these challenges. Ultimately, as we move forward, future research endeavors should aim to pinpoint the most effective amino-acid-targeted therapies, determining the optimal dosage and mode of administration. This exploration is essential for maximizing the reprogramming effects, ultimately contributing to the enhancement of cardiovascular-kidney-metabolic health in offspring.

The NOS/NO System in Renal Programming and Reprogramming

Nitric oxide (NO) is a gaseous signaling molecule with renoprotective properties. NO can be produced in NO synthase (NOS)-dependent or -independent manners. NO deficiency plays a decisive role in chronic kidney disease (CKD). Kidney development can be affected in response to adverse intrauterine conditions that induce renal programming, thereby raising the risk of developing CKD in adulthood. Conversely, detrimental programming processes could be postponed or halted prior to the onset of CKD by early treatments, namely reprogramming. The current review provides an overview of the NOS/NO research performed in the context of renal programming and reprogramming. NO deficiency has been increasingly found to interact with the different mechanisms behind renal programming, such as oxidative stress, aberrant function of the renin-angiotensin system, disturbed nutrient-sensing mechanisms, dysregulated hydrogen sulfide signaling, and gut microbiota dysbiosis. The supplementation of NOS substrates, the inhibition of asymmetric dimethylarginine (ADMA), the administration of NO donors, and the enhancement of NOS during gestation and lactation have shown beneficial effects against renal programming in preclinical studies. Although human data on maternal NO deficiency and offspring kidney disease are scarce, experimental data indicate that targeting NO could be a promising reprogramming strategy in the setting of renal programming.

Amino Acids and Developmental Origins of Hypertension

During pregnancy, amino acids are important biomolecules that play essential roles in fetal growth and development. Imbalanced amino acid intake during gestation may produce long-term morphological or functional changes in offspring, for example, developmental programming that increases the risk of developing hypertension in later life. Conversely, supplementation with specific amino acids could reverse the programming processes in early life, which may counteract the rising epidemic of hypertension. This review provides an overview of the evidence supporting the importance of amino acids during pregnancy and fetal development, the impact of amino acids on blood pressure regulation, insight from animal models in which amino acids were used to prevent hypertension of developmental origin, and interactions between amino acids and the common mechanisms underlying development programming of hypertension. A better understanding of the pathophysiological roles of specific amino acids and their interactions in developmental programming of hypertension is essential so that pregnant mothers are able to benefit from accurate amino acid supplementation during pregnancy in order to prevent hypertension development in their children.

Impact of Arginine Nutrition and Metabolism during Pregnancy on Offspring Outcomes

By serving as a precursor for the synthesis of nitric oxide, polyamines, and other molecules with biological importance, arginine plays a key role in pregnancy and fetal development. Arginine supplementation is a potential therapy for treating many human diseases. An impaired arginine metabolic pathway during gestation might produce long-term morphological or functional changes in the offspring, namely, developmental programming to increase vulnerability to developing a variety of non-communicable diseases (NCDs) in later life. In contrast, reprogramming is a strategy that shifts therapeutic interventions from adulthood to early-life, in order to reverse the programming processes, which might counterbalance the rising epidemic of NCDs. This review presented the role of arginine synthesis and metabolism in pregnancy. We also provided evidence for the links between an impaired arginine metabolic pathway and the pathogenesis of compromised pregnancy and fetal programming. This was followed by reprogramming strategies targeting the arginine metabolic pathway, to prevent the developmental programming of NCDs. Despite emerging evidence from experimental studies showing that targeting the arginine metabolic pathway has promise as a reprogramming strategy in pregnancy to prevent NCDs in the offspring, these results need further clinical application.

The Good, the Bad, and the Ugly of Pregnancy Nutrients and Developmental Programming of Adult Disease

Maternal nutrition plays a decisive role in developmental programming of many non-communicable diseases (NCDs). A variety of nutritional insults during gestation can cause programming and contribute to the development of adult-onset diseases. Nutritional interventions during pregnancy may serve as reprogramming strategies to reverse programming processes and prevent NCDs. In this review, firstly we summarize epidemiological evidence for nutritional programming of human disease. It will also discuss evidence from animal models, for the common mechanisms underlying nutritional programming, and potential nutritional interventions used as reprogramming strategies.

The Double-Edged Sword Effects of Maternal Nutrition in the Developmental Programming of Hypertension

Hypertension is a growing global epidemic. Developmental programming resulting in hypertension can begin in early life. Maternal nutrition status has important implications as a double-edged sword in the developmental programming of hypertension. Imbalanced maternal nutrition causes offspring's hypertension, while specific nutritional interventions during pregnancy and lactation may serve as reprogramming strategies to reverse programming processes and prevent the development of hypertension. In this review, we first summarize the human and animal data supporting the link between maternal nutrition and developmental programming of hypertension. This review also presents common mechanisms underlying nutritional programming-induced hypertension. This will be followed by studies documenting nutritional interventions as reprogramming strategies to protect against hypertension from developmental origins. The identification of ideal nutritional interventions for the prevention of hypertension development that begins early in life will have a lifelong impact, with profound savings in the global burden of hypertension.

Autonomic and Renal Alterations in the Offspring of Sleep-Restricted Mothers During Late Pregnancy

OBJECTIVES

Considering that changes in the maternal environment may result in changes in progeny, the aim of this study was to investigate the influence of sleep restriction during the last week of pregnancy on renal function and autonomic responses in male descendants at an adult age.

METHODS

After confirmation of pregnancy, female Wistar rats were randomly assigned to either a control or a sleep restriction group. The sleep-restricted rats were subjected to sleep restriction using the multiple platforms method for over 20 hours per day between the 14th and 20th day of pregnancy. After delivery, the litters were limited to 6 offspring that were designated as offspring from control and offspring from sleep-restricted mothers. Indirect measurements of systolic blood pressure (BPi), renal plasma flow, glomerular filtration rate, glomerular area and number of glomeruli per field were evaluated at three months of age. Direct measurements of cardiovascular function (heart rate and mean arterial pressure), cardiac sympathetic tone, cardiac parasympathetic tone, and baroreflex sensitivity were evaluated at four months of age.

RESULTS

The sleep-restricted offspring presented increases in BPi, glomerular filtration rate and glomerular area compared with the control offspring. The sleep-restricted offspring also showed higher basal heart rate, increased mean arterial pressure, increased sympathetic cardiac tone, decreased parasympathetic cardiac tone and reduced baroreflex sensitivity.

CONCLUSIONS

Our data suggest that reductions in sleep during the last week of pregnancy lead to alterations in cardiovascular autonomic regulation and renal morpho-functional changes in offspring, triggering increases in blood pressure.

Chronic widespread dermatophytosis due to Trichophyton rubrum: a syndrome associated with a Trichophyton-specific functional defect of phagocytes

Dermatophytes are agents of typically benign superficial infections. However, an increasing number of severe infections in immunocompromised hosts has been reported. We aimed to understand the factors underlying the existence of a cohort of patients presenting with chronic widespread dermatophytosis (CWD) due to Trichophyton rubrum, but with no signs of immunodeficiency. Their disease is usually recurrent and difficult to manage. Fourteen patients meeting the following criteria for CWD were studied: T. rubrum culture-proven skin lesions of ≥10 cm in at least one dimension; the involvement of at least three non-contiguous localizations of >1 year's duration; and no predisposing conditions. For comparison, we also studied 13 acute Tinea pedis patients. Macrophages and neutrophils were isolated and tested for T. rubrum conidia phagocytic and killing activity. H2O2, NO, and pro- and anti-inflammatory cytokine release were measured. All experiments were run with age- and sex-matched healthy donors' cells in parallel. CWD patients' macrophages and neutrophils presented with reduced T. rubrum-phagocytic and killing abilities, and reduced H2O2 and NO release when compared with those of healthy donors. CWD patients' macrophages secreted lower levels of the proinflammatory cytokines interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor (TNF)-α, but enhanced levels of the anti-inflammatory cytokine IL-10. Neutrophil secretion closely followed this unbalanced pattern. In contrast, responses to the positive controls zymosan, lipopolysaccharide, and phorbol myristate acetate were comparable with those of healthy donors. The same experiments were performed with macrophages and neutrophils from the acute Tinea pedis patients and showed no differences when compared with the matched healthy donors. Patients with CWD have a T. rubrum-related functional deficiency of phagocytes and may represent a distinct clinical entity in the complex spectrum of the Trichophyton-host interaction.

Emerging role of angiotensin type 2 receptor (AT2R)/Akt/NO pathway in vascular smooth muscle cell in the hyperthyroidism

Hyperthyroidism is characterized by increased vascular relaxation and decreased vascular contraction and is associated with augmented levels of triiodothyronine (T3) that contribute to the diminished systemic vascular resistance found in this condition. T3 leads to augmented NO production via PI3K/Akt signaling pathway, which in turn causes vascular smooth muscle cell (VSMC) relaxation; however, the underlying mechanisms involved remain largely unknown. Evidence from human and animal studies demonstrates that the renin-angiotensin system (RAS) plays a crucial role in vascular function and also mediates some of cardiovascular effects found during hyperthyroidism. Thus, in this study, we hypothesized that type 2 angiotensin II receptor (AT2R), a key component of RAS vasodilatory actions, mediates T3 induced-decreased vascular contraction. Marked induction of AT2R expression was observed in aortas from T3-induced hyperthyroid rats (Hyper). These vessels showed decreased protein levels of the contractile apparatus: α-actin, calponin and phosphorylated myosin light chain (p-MLC). Vascular reactivity studies showed that denuded aortic rings from Hyper rats exhibited decreased maximal contractile response to angiotensin II (AngII), which was attenuated in aortic rings pre-incubated with an AT2R blocker. Further study showed that cultured VSMC stimulated with T3 (0.1 µmol/L) for 24 hours had increased AT2R gene and protein expression. Augmented NO levels and decreased p-MLC levels were found in VSMC stimulated with T3, both of which were reversed by a PI3K/Akt inhibitor and AT2R blocker. These findings indicate for the first time that the AT2R/Akt/NO pathway contributes to decreased contractile responses in rat aorta, promoted by T3, and this mechanism is independent from the endothelium.

Role of fetal programming in the development of hypertension

Epidemiological studies have suggested that size at birth contributes to increased cardiovascular disease (CVD) risk in later life. Findings from experimental studies are providing insight into the mechanisms linking impaired fetal growth and the increased risk of CVD and hypertension in adulthood. This article summarizes potential mechanisms involved in the fetal programming of hypertension and CVD, including alterations in the organs and regulatory systems critical to long-term control of sodium and volume homeostasis.

Thyroid hormone stimulates NO production via activation of the PI3K/Akt pathway in vascular myocytes

AIMS

Thyroid hormone (TH) rapidly relaxes vascular smooth muscle cells (VSMCs). However, the mechanisms involved in this effect remain unclear. We hypothesize that TH-induced rapid vascular relaxation is mediated by VSMC-derived nitric oxide (NO) production and is associated with the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signalling pathway.

METHODS AND RESULTS

NO levels were determined using a NO-specific fluorescent dye (DAF-2) and nitrite (NO2-) levels. Expression of NO synthase (NOS) isoforms and proteins of the PI3K/Akt pathway was determined by both western blotting and immunocytochemistry. Myosin light chain (MLC) phosphorylation levels were also investigated by western blotting. Exposure of cultured VSMCs from rat thoracic aortas to triiodothyronine (T3) resulted in a significant decrease of MLC phosphorylation levels. T3 also induced a rapid increase in Akt phosphorylation and increased NO production in a dose-dependent manner (0.001-1 microM). VSMCs stimulated with T3 for 30 min showed an increase in the expression of all three NOS isoforms and augmented NO production, effects that were prevented by inhibitors of PI3K. Vascular reactivity studies showed that vessels treated with T3 displayed a decreased response to phenylephrine, which was reversed by NOS inhibition. These data suggest that T3 treatment induces greater generation of NO both in aorta and VSMCs and that this phenomenon is endothelium independent. In addition, these findings show for the first time that the PI3K/Akt signalling pathway is involved in T3-induced NO production by VSMCs, which occurs with expressive participation of inducible and neuronal NOS.

CONCLUSION

Our data strongly indicate that T3 causes NO-dependent rapid relaxation of VSMC and that this effect is mediated by the PI3K/Akt signalling pathway.

Intrauterine growth restriction: fetal programming of hypertension and kidney disease

The etiology of hypertension historically includes 2 components: genetics and lifestyle. However, recent epidemiologic studies report an inverse relationship between birth weight and hypertension suggesting that a suboptimal fetal environment may also contribute to increased disease in later life. Experimental studies support this observation and indicate that cardiovascular/kidney disease originates in response to fetal adaptations to adverse conditions during prenatal life.

Maternal supplementation with citrulline increases renal nitric oxide in young spontaneously hypertensive rats and has long-term antihypertensive effects

NO deficiency is associated with development of hypertension. Defects in the renal citrulline-arginine pathway or arginine reabsorption potentially reduce renal NO in prehypertensive spontaneously hypertensive rats (SHRs). Hence, we investigated genes related to the citrulline-arginine pathway or arginine reabsorption, amino acid pools, and renal NO in 2-week-old prehypertensive SHRs. In addition, because perinatally supporting NO availability reduces blood pressure in SHRs, we supplemented SHR dams during pregnancy and lactation with citrulline, the rate-limiting amino acid for arginine synthesis. In female offspring, gene expression of argininosuccinate synthase (involved in renal arginine synthesis) and renal cationic amino acid Y-transporter (involved in arginine reabsorption) were both decreased in 2-day and 2-week SHRs compared with normotensive WKY, although no abnormalities in amino acid pools were observed. In addition, 2-week-old female SHRs had much less NO in their kidneys (0.46+/-0.01 versus 0.68+/-0.05 nmol/g of kidney weight, respectively; P<0.001) but not in their heart. Furthermore, perinatal supplementation with citrulline increased renal NO to 0.59+/-0.02 nmol/g of kidney weight (P<0.001) at 2 weeks and persistently ameliorated the development of hypertension in females and until 20 weeks in male SHR offspring. Defects in both the renal citrulline-arginine pathway and in arginine reabsorption precede hypertension in SHRs. We propose that the reduced cationic amino acid transporter disables the developing SHR kidney to use arginine reabsorption to compensate for reduced arginine synthesis, resulting in organ-specific NO deficiency. This early renal deficiency and its adverse sequels can be corrected by perinatal citrulline supplementation persistently in female and transiently in male SHRs.

The influence of L-arginine on blood pressure, vascular nitric oxide and renal morphometry in the offspring from diabetic mothers

The present study was designed to evaluate the effects of L-arginine (L-arg) supplementation on blood pressure, vascular nitric oxide content, and renal morphometry in the adult offspring from diabetic mothers. Diabetes mellitus was induced in female rats with a single dose of streptozotocin (50 mg/kg), before mating. The offspring was divided into four groups: group C (controls); group DO (diabetic offspring); group CA (controls receiving 2% L-arg solution dissolved in 2% sucrose in the drinking water) and group DA (DO receiving the L-arg solution). Oral supplementation began after weaning and continued until the end of the experiments. In DO, hypertension was observed, from 3 mo on. In DA, pressure levels were not different from C and CA. In 6-mo-old animals, basal NO production (assessed by DAF-2) was significantly depressed in DO in comparison to controls. The NO production was significantly increased after stimulation with Ach or BK in all groups, the increase being greater in control than in DO rats. L-arg was able to improve the NO production and to prevent the glomerular hypertrophy in the DO. Our data suggest that the bioavailability of NO is reduced in the DO, because L-arg corrected both the hypertension and glomerular hypertrophy.

Maternal diabetes mellitus--early consequences for the offspring

Although several studies have focused on the effects of nutritional status during intrauterine development, few have addressed the impact of maternal diabetes mellitus on renal function and morphology in the young offspring. In the present study, renal morpho-functional aspects were studied in the offspring of diabetic rats. Diabetes was induced in female rats with a single dose of streptozotocyn (STZ), 10 days before mating. After weaning, the offspring (DO) had free access to food and water. Arterial blood pressure was measured, by tail plethysmography, from 2 months on. Renal function was evaluated in 2- and 3-month-old rats in the DO group and in controls (C). Analysis of renal morphology was carried out in newborn and in 1-, 2- and 3-month-old rats in both groups. Although the nephron number was not changed in the DO group, glomerular hypertrophy was observed from 2 months on. At the same age, the glomerular filtration rate was significantly reduced in DO, and blood pressure was significantly increased, when compared to C. Glucose tolerance test (GTT) from DO showed a different profile when compared to C. The number of PCNA positive cells in renal tissue was similar in both groups. Our data suggests that exposure to intrauterine diabetes may be an important cause of both impaired renal function and hypertension in offspring, without changes in the nephron number.

Consequences of Intrauterine Growth Restriction for the Kidney

Low birth weight due to intrauterine growth restriction is associated with various diseases in adulthood, such as hypertension, cardiovascular disease, insulin resistance and end-stage renal disease. The purpose of this review is to describe the effects of intrauterine growth restriction on the kidney. Nephrogenesis requires a fine balance of many factors that can be disturbed by intrauterine growth restriction, leading to a low nephron endowment. The compensatory hyperfiltration in the remaining nephrons results in glomerular and systemic hypertension. Hyperfiltration is attributed to several factors, including the renin-angiotensin system (RAS), insulin-like growth factor (IGF-I) and nitric oxide. Data from human and animal studies are presented, and suggest a faltering IGF-I and an inhibited RAS in intrauterine growth restriction. Hyperfiltration makes the kidney more vulnerable during additional kidney disease, and is associated with glomerular damage and kidney failure in the long run. Animal studies have provided a possible therapy with blockage of the RAS at an early stage in order to prevent the compensatory glomerular hyperfiltration, but this is far from being applicable to humans. Research is needed to further unravel the effect of intrauterine growth restriction on the kidney.

Fetal programming of hypertension

Numerous epidemiological studies suggest an inverse relationship between low birth weight (LBW) and hypertension, an observation now supported by numerous animal studies. The mechanisms linking LBW and hypertension appear to be multifactorial and involve alterations in the normal regulatory systems and renal functions involved in the long-term control of arterial pressure. Recent studies using animal models of fetal programming suggest that programming during fetal life occurs in response to an adverse fetal environment and results in permanent adaptive responses that lead to structural and physiological alterations and the subsequent development of hypertension. This review summarizes the adaptive responses observed in the different models used to induce a suboptimal fetal environment and discusses insights into the mechanisms mediating the fetal programming of hypertension.

Long-term effects of maternal diabetes on vascular reactivity and renal function in rat male offspring

Fetal growth impairment can occur in pregnancy complicated by diabetes. Although several studies have focused the effects of nutritional status on intrauterine development, the long-term impact of maternal diabetes on vascular and renal function in the offspring is poorly investigated. In the present study, blood pressure profiles and renal function parameters were investigated in the offspring of diabetic rats (DO). Female rats were made diabetic throughout gestation with a single dose of streptozotocyn (STZ) 10 d before mating. After weaning, the offspring had free access to food and water. Arterial pressure was evaluated every 15 d. Functional and morphometric kidney studies were performed in newborn, 3, 6 and 12-mo-old male rats in DO and in controls, C. Although maternal diabetes did not affect nephron number in the young adult rat, glomerular hypertrophy developed from 3 mo on. Glomerular Filtration Rate and Renal Plasma Flow were observed to be significantly decreased in DO when compared with C, from 3 mo on. In DO, hypertension was observed from 8 wk on and persisted elevated throughout the experimental period (12 mo). Vascular reactivity, evaluated in mesenteric arterial bed showed a decreased endothelium-dependent vasodilatation in 12-mo-old DO animals, while preserved response to sodium nitroprusside was demonstrated. Our data show that exposure to intrauterine diabetes induced by STZ does not affect nephron number in the young offspring but can cause permanent changes in Nitric Oxide (NO)-related vascular response, which, in turn may accelerate the natural age-related nephron loss.

Effects of intrauterine food restriction and long-term dietary supplementation with L-arginine on age-related changes in renal function and structure of rats

We have previously demonstrated that restricting intrauterine food by 50% in 3-mo-old rats produced lower nephron numbers and early-onset hypertension, the latter being normalized by L-arginine administration. In 18-mo-old rats, such restriction increased glomerulosclerosis. In this study, we expanded our investigation, evaluating functional, morphologic, and immunohistochemical parameters in intrauterine-food-restricted 18-mo-old rats, either receiving L-arginine (RA18) or not (R18). Age-matched, non-food-restricted controls were assigned to similar groups with L-arginine (CA18) and without (C18). After weaning, L-arginine was given daily for 17 mo. No functional or morphologic changes were observed in C18 rats. The R18 rats developed early-onset hypertension, which persisted throughout the observation period, as well as significant proteinuria from 12 mo on. In RA18 rats, L-arginine decreased both blood pressure levels and proteinuria, and glomerular diameter was significantly smaller than in R18 rats (115.63 +/- 2.2 versus 134.8 +/- 1.0 mum, p < 0.05). However, in RA18 rats, glomerular filtration rate remained depressed. Although L-arginine prevented glomerulosclerosis (R18 = 14%, RA18 = 4%; p < 0.05), glomerular expression of fibronectin and desmin was still greater in RA18 rats than in controls. Our data show that, although L-arginine prevented hypertension and proteinuria, glomerular injury still occurred, suggesting that intrauterine food restriction may be one of the leading causes of impaired renal function in adult life.

Programming blood pressure in adult SHR by shifting perinatal balance of NO and reactive oxygen species toward NO: the inverted Barker phenomenon

The “programming hypothesis” proposes that an adverse perinatal milieu leads to adaptation that translates into cardiovascular disease in adulthood. The balance between nitric oxide (NO) and reactive oxygen species (ROS) is disturbed in cardiovascular diseases, including hypertension. Conceivably, this balance is also disturbed in pregnancy, altering the fetal environment; however, effects of perinatal manipulation of NO and ROS on adult blood pressure (BP) are unknown. In spontaneously hypertensive rats (SHR), NO availability is decreased and ROS are increased compared with normotensive Wistar-Kyoto rats, and, despite the genetic predisposition, the perinatal environment can modulate adult BP. Our hypothesis is that a disturbed NO-ROS balance in the SHR dam persistently affects BP in her offspring. Dietary supplements, which support NO formation and scavenge ROS, administered during pregnancy and lactation resulted in persistently lower BP for up to 48 wk in SHR offspring. The NO donor molsidomine and the superoxide dismutase mimic tempol-induced comparable effects. Specific inhibition of inducible nitric oxide synthase (NOS) reduces BP in adult SHR, suggesting that inducible NOS is predominantly a source of ROS in SHR. Indeed, inducible NOS inhibition in SHR dams persistently reduced BP in adult offspring. Persistent reductions in BP were accompanied by prevention of proteinuria in aged SHR. We propose that in SHR the known increase in ANG II type 1 receptor density during development leads to superoxide production, which enhances inducible NOS activity. The relative shortage of substrate and cofactors leads to uncoupling of inducible NOS, resulting in superoxide production, activating transcription factors that subsequently again increase inducible NOS expression. This vicious circle probably is perpetuated into adult life.

L-arginine and phosphodiesterase (PDE) inhibitors counteract fibrosis in the Peyronie's fibrotic plaque and related fibroblast cultures

Inducible nitric oxide synthase (iNOS) is expressed in both the fibrotic plaque of Peyronie's disease (PD) in the human, and in the PD-like plaque elicited by injection of TGFbeta1 into the penile tunica albuginea (TA) of the rat. Long-term inhibition of iNOS activity, presumably by blocking nitric oxide (NO)- and cGMP-mediated effects triggered by iNOS expression, exacerbates tissue fibrosis through an increase in: (a) collagen synthesis, (b) levels of reactive oxygen species (ROS), and (c) the differentiation of fibroblasts into myofibroblasts. We have now investigated whether: (a) phosphodiesterase (PDE) isoforms, that regulate the interplay of cGMP and cAMP pathways, are expressed in both the human and rat TA; and (b) L-arginine, that stimulates NOS activity and hence NO synthesis, and PDE inhibitors, that increase the levels of cGMP and/or cAMP, can inhibit collagen synthesis and induce fibroblast/myofibroblast apoptosis, thus acting as antifibrotic agents. We have found by immunohistochemistry, RT/PCR, and Western blot that PDE5A-3 and PDE4A, B, and D variants are indeed expressed in human and rat normal TA and PD plaque tissue, as well as in their respective fibroblast cultures. As expected, in the PD fibroblast cultures, pentoxifylline (non-specific cAMP-PDE inhibitor) increased cAMP levels without affecting cGMP levels, whereas sildenafil (PDE5A inhibitor) raised cGMP levels. Both agents and L-arginine reduced the expression of collagen I (but not collagen III) and the myofibroblast marker, alpha-smooth muscle actin, as determined by immunocytochemistry and quantitative image analysis. These effects were mimicked by incubation with 8-Br-cGMP, which in addition increased apoptosis, as measured by TUNEL. When L-arginine (2.25 g/kg/day), pentoxifylline (10 mg/kg/day), or sildenafil (10 mg/kg/day) was given individually in the drinking water for 45 days to rats with a PD-like plaque induced by TGF beta1, each treatment resulted in a 80-95% reduction in both plaque size and in the collagen/fibroblast ratio, as determined by Masson trichrome staining. Both sildenafil and pentoxiphylline stimulated fibroblast apoptosis within the TA. Our results support the hypothesis that the increase in NO and/or cGMP/cAMP levels by long-term administration of nitrergic agents or inhibitors of PDE, may be effective in reversing the fibrosis of PD, and more speculatively, other fibrotic conditions.

Tetrahydrobiopterin improves endothelial dysfunction and vascular oxidative stress in microvessels of intrauterine undernourished rats

In the present study, we investigated the effects of the exogenous application of tetrahydrobiopterin on the endothelium-dependent vasorelaxation and superoxide anion generation in the mesenteric microvessels of intrauterine undernourished rats. In addition, we investigated the presence of peroxynitrite in these rats by evaluation of nitrotyrosine-containing proteins, a stable end-product of peroxynitrite oxidation. For this, female pregnant Wistar rats were fed either normal or 50% of the normal intake diets during the whole gestational period. Male offspring (16 weeks of age) were studied to assess microvascular reactivity, superoxide production using a hydroethidine staining assay, nitric oxide synthase (NOS) activity and nitric oxide (NO) production. Western blot analysis was used to quantify nitrotyrosine-containing proteins and relative multiplex RT-PCR analysis for endothelial NOS (eNOS) mRNA expression. Superfusion with tetrahydrobiopterin significantly decreased superoxide generation and improved vascular function. Intrauterine malnutrition induced a decrement of NOS activity and NO production without affecting the gene expression of eNOS. However, incubation with tetrahydrobiopterin significantly improved NO production after stimulation with acetylcholine or bradykinin in intrauterine undernourished rats. The fact that the nitrotyrosine-containing proteins were increased could, at first sight, suggest that the peroxynitrite is the mediator responsible for the excessive oxidation and depletion of tetrahydrobiopterin. Our study shows that exogenous application of tetrahydrobiopterin leads to a significant improvement of endothelium-dependent vasodilatation, enhanced NO production and decreased superoxide generation in microvessels of intrauterine undernourished rats. Since we found a decrease in NOS activity without an alteration in the gene expression of eNOS, we suggest that impaired NOS-dependent responses of mesenteric arterioles are related to the impairment of tetrahydrobiopterin pathways.

Stromal cell-derived factor-1 production by spleen cells is affected by nitric oxide in protective immunity against blood-stage Plasmodium chabaudi CR in C57BL/6j mice

Malaria, a major endemic tropical disease, is caused by the infection of blood cells by Plasmodium protozoa. Most patients control their parasitemia by a not fully understood spleen-dependent mechanism. SDF-1alpha is a chemokine produced by stromal cells such as reticular spleen cells. Nitric oxide (NO) has several immune functions, including killing of intracellular pathogens and its function in malaria is debated. We have previously shown that SDF-1alpha production peaks during the ascending parasitemia in Plasmodium chabaudi infection and its supplementation in lethal models could reduce the parasitemia. In the present study, we analyzed SDF-1 production by spleen cells as related to NO metabolism in the P. chabaudi rodent malaria model using IFN-gamma; TNFR and iNOS-knockout mice or iNOS-blocked, L-NAME- or aminoguanidine-treated mice. Parasitemia and production of SDF-1alpha and SDF-1beta were determined by RT-PCR. In vitro NO production by spleen adherent cells was also tested. The data showed that parasitemia was less intense in both iNOS(-/-) or NO-inhibited mice than in controls, with increased and long-lasting production of SDF-1alpha mRNA. In the absence of cytokines involved in the final regulation of NO production by effector cells, as is the case for TNFR(-/-) and GKO mice, the infection progressed in an uncontrolled manner regardless of SDF-1alpha production, suggesting that these cytokines must be involved in the control of parasitemia after the SDF-1alpha dependent process. The SDF-1beta isoform was constitutive in all experiments, with elevated levels only clearly seen in TNFR(-/-) mice. We conclude that SDF-1 is involved in the promotion of parasitemia control in malaria, and excessive NO could affect its production.