Increased serum fractalkine in systemic sclerosis. Down-regulation by prostaglandin E1.

OBJECTIVES: To evaluate serum levels of fractalkine (FKN), a mediator of leukocyte transmigration, C-reactive protein (CRP) and expression of integrins CD11a and CD49d on peripheral blood lymphocytes in systemic sclerosis (SSc) and to investigate whether they are modulated by intravenous prostaglandin E1 (PGE1). METHODS: Serum levels of fractalkine and C-reactive protein and expression of CD11a and CD49d on peripheral blood lymphocytes were assessed in 50 SSc patients and in 18 healthy controls. In 25 SSc patients studied parameters were evaluated also after 3 consecutive daily PGE1 infusions (20 microg-40 microg-60 microg) and after 4 weeks. RESULTS: In SSc fractalkine basal level was significantly higher than in controls (9.04+/-1.79 ng/ml vs. 1.17+/-0.1 ng/ml; p<0.0001) and decreased significantly after PGE1 (5.16+/-1.27 ng/ml, p<0.05). After four weeks fractalkine level was still significantly lower than baseline 7.70+/-2.19 ng/ml (p<0.05). Basal percentage of CD11a (+) nor CD49d (+) lymphocytes in SSc (82.38+/-1.60%, 70.74+/-1.68%, respectively) did not differ from controls (85.73+/-2.04%, 75.62+/-2.48%; respectively, p>0.05). PGE1 treatment resulted in decrease of both CD11a (+) (67.72+/-3.34%, p<0.0001) and CD49d (+) lymphocytes (65.32+/-1.62%, p<0.0001). After 4 weeks the percentage of CD11a (+) and CD49d (+) lymphocytes remained significantly lower than at baseline (77.80+/-2.47% and 65.32+/-1.62%, respectively, both p<0.001). In SSc CRP basal level was significantly higher than in controls (4.70+/-2.01 mg/dl vs. 1.40+/-1.79 mg/dl, p<0.005) and reduced significantly after PGE1 (3.39+/-2.06 mg/dl, p<0.05). After 4 weeks, CRP level (4.38+/-2.19 ng/ml) was significantly lower than baseline (p<0.05). CONCLUSION: Fractalkine may play an important role in the pathogenesis of vascular dysfunction in systemic sclerosis. Prostaglandin E1 down-regulates serum fractalkine level, as well as CD11a and CD49d expression on peripheral blood lymphocytes, which suggests additional mechanisms in which this vasodilatatory agent exerts its efficacy in systemic sclerosis.

Nitric oxide modulates renal sensory nerve fibers by mechanisms related to substance P receptor activation.

UNLABELLED: Nerve terminals containing neuronal nitric oxide synthase (nNOS) are localized in the renal pelvic wall where the sensory nerves containing substance P and calcitonin gene-related peptide (CGRP) are found. We examined whether nNOS is colocalized with substance P and CGRP. All renal pelvic nerve fibers that contained nNOS-like immunoreactivity (-LI) also contained substance P-LI and CGRP-LI. In anesthetized rats, renal pelvic perfusion with the nNOS inhibitor S-methyl-L-thiocitrulline (L-SMTC, 20 microM) prolonged the afferent renal nerve activity (ARNA) response to a 3-min period of increased renal pelvic pressure from 5 +/- 0.4 to 21 +/- 2 min (P < 0.01, n = 14). The magnitude of the ARNA response was unaffected by L-SMTC. Similar effects were produced by N(omega)-nitro-L-arginine methyl ester (L-NAME) but not D-NAME. Increasing renal pelvic pressure produced similar increases in renal pelvic release of substance P before and during L-SMTC, from 5.9 +/- 1.4 to 13.6 +/- 4.2 pg/min before and from 4.9 +/- to 12.6 +/- 2.7 pg/min during L-SMTC. L-SMTC also prolonged the ARNA response to renal pelvic perfusion with substance P (3 microM) from 1.2 +/- 0.2 to 5.6 +/- 1.1 min (P < 0.01, n = 9) without affecting the magnitude of the ARNA response. IN CONCLUSION: activation of NO may function as an inhibitory neurotransmitter regulating the activation of renal mechanosensory nerve fibers by mechanisms related to activation of substance P receptors.

Activation of renal mechanosensitive neurons involves bradykinin, protein kinase C, PGE(2), and substance P.

Increased renal pelvic pressure or bradykinin increases afferent renal nerve activity (ARNA) via PGE(2)-induced release of substance P. Protein kinase C (PKC) activation increases ARNA, and PKC inhibition blocks the ARNA response to bradykinin. We now examined whether bradykinin mediates the ARNA response to increased renal pelvic pressure by activating PKC. In anesthetized rats, the ARNA responses to increased renal pelvic pressure were blocked by renal pelvic perfusion with the bradykinin B(2)-receptor antagonist HOE 140 and the PKC inhibitor calphostin C by 76 +/- 8% (P < 0.02) and 81 +/- 5% (P < 0.01), respectively. Renal pelvic perfusion with 4beta-phorbol 12,13-dibutyrate (PDBu) to activate PKC increased ARNA 27 +/- 4% and renal pelvic release of PGE(2) from 500 +/- 59 to 1, 113 +/- 183 pg/min and substance P from 10 +/- 2 to 30 +/- 2 pg/min (all P < 0.01). Indomethacin abolished the increases in substance P release and ARNA. The PDBu-mediated increase in ARNA was also abolished by the substance P-receptor antagonist RP 67580. We conclude that bradykinin contributes to the activation of renal pelvic mechanosensitive neurons by activating PKC. PKC increases ARNA via a PGE(2)-induced release of substance P.

Cyclooxygenase-2 involved in stimulation of renal mechanosensitive neurons.

Stretching of the renal pelvic wall activates renal mechanosensitive neurons, resulting in an increase in afferent renal nerve activity (ARNA). Prostaglandin (PG)E(2) plays a crucial role in the activation of renal mechanosensitive neurons through facilitation of the release of substance P from the sensory neurons in the renal pelvic wall. Because wall stretch may induce cyclooxygenase-2 activity, we examined whether cyclooxygenase-2 was expressed in the renal pelvic wall and whether activation of cyclooxygenase-2 contributed to the ARNA response produced through increased renal pelvic pressure. In situ hybridization showed a strong cyclooxygenase-2 mRNA signal in the papilla and subepithelial layer of the renal pelvic wall from time control kidneys and from kidneys exposed to 15 minutes of increased renal pelvic pressure in anesthetized surgically operated rats. In anesthetized rats, an increase in renal pelvic pressure increased ARNA by 40+/-2% and increased renal pelvic release of PGE(2) from 289+/-46 to 1379+/-182 pg/min (P<0.01). Renal pelvic perfusion with the cyclooxygenase-2 inhibitor etodolac reduced the increases in ARNA and PGE(2) by 66+/-7% and 55+/-13%, respectively (P<0.01). Likewise, the cyclooxygenase-2 inhibitor 5, 5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5H)-furanone reduced the increases in ARNA and PGE(2) by 43+/-5% and 47+/-8%, respectively. We conclude that cyclooxygenase-2 is expressed in the renal pelvic wall and that the activation of cyclooxygenase-2 contributes to the stimulation of renal mechanosensitive neurons in the pelvic wall.

PGE2 increases substance P release from renal pelvic sensory nerves via activation of N-type calcium channels.

Activation of renal pelvic sensory nerves by increased pelvic pressure results in a renal pelvic release of substance P that is dependent on intact prostaglandin synthesis. An isolated renal pelvic wall preparation was used to examine whether PGE2 increases the release of substance P from renal pelvic sensory nerves and by what mechanisms. The validity of the model was tested by examining whether 50 mM KCl increased substance P release from the pelvic wall. Fifty millimolar KCl produced an increase in substance P release, from 9.6 +/- 1.6 to 26.8 +/- 4.0 pg/min, P < 0.01, that was blocked by the L-type calcium blocker verapamil (10 microM). PGE2 (0.14 microM) increased the release of substance P from the pelvic wall from 8.9 +/- 0.9 to 20.6 +/- 3.3 pg/min, P < 0.01. PGE2 failed to increase substance P release in a calcium-free medium. The PGE2-induced substance P release was blocked by the N-type calcium blocker omega-conotoxin (0.1 microM) but was unaffected by verapamil. In conclusion, PGE2 increases the release of substance P from renal pelvic sensory nerves by a calcium-dependent mechanism that requires influx of calcium via N-type calcium channels.

Fos expression in rat brain during depletion-induced thirst and salt appetite.

The expression of Fos protein (Fos immunoreactivity, Fos-ir) was mapped in the brain of rats subjected to an angiotensin-dependent model of thirst and salt appetite. The physiological state associated with water and sodium ingestion was produced by the concurrent subcutaneous administration of the diuretic furosemide (10 mg/kg) and a low dose of the angiotensin-converting enzyme (ACE) inhibitor captopril (5 mg/kg; Furo/Cap treatment). The animals were killed 2 h posttreatment, and the brains were processed for Fos-ir to assess neural activation. Furo/Cap treatment significantly increased Fos-ir density above baseline levels both in structures of the lamina terminalis and hypothalamus known to mediate the actions of ANG II and in hindbrain regions associated with blood volume and pressure regulation. Furo/Cap treatment also typically increased Fos-ir density in these structures above levels observed after administration of furosemide or captopril separately. Fos-ir was reduced to a greater extent in forebrain than in hindbrain areas by a dose of captopril (100 mg/kg sc) known to block the actions of ACE in the brain. The present work provides further evidence that areas of lamina terminalis subserve angiotensin-dependent thirst and salt appetite.

Renal substance P-containing neurons and substance P receptors impaired in hypertension.

In normotensive rats, increased renal pelvic pressure stimulates the release of prostaglandin E and substance P, which in turn leads to an increase in afferent renal nerve activity (ARNA) and a contralateral natriuresis, a contralateral inhibitory renorenal reflex. In spontaneously hypertensive rats (SHR), increasing renal pelvic pressure failed to increase afferent renal nerve activity. The inhibitory nature of renorenal reflexes indicates that impaired renorenal reflexes could contribute to increased sodium retention in SHR. Phorbol esters, known to activate protein kinase C, increase afferent renal nerve activity in Wistar-Kyoto rats (WKY) but not in SHR. We examined the mechanisms involved in the impaired responses to renal sensory receptor activation in SHR. The phorbol ester 4beta-phorbol 12,13-dibutyrate increased renal pelvic protein kinase C activity similarly in SHR and WKY. Increasing renal pelvic pressure increased afferent renal nerve activity in WKY (27+/-2%) but not in SHR. Renal pelvic release of prostaglandin E increased similarly in WKY and SHR, from 0.8+/-0.1 to 2.0+/-0.4 ng/min and 0.7+/-0.1 to 1.4+/-0.2 ng/min. Renal pelvic release of substance P was greater (P<.01) in WKY, from 16.3+/-3.8 to 41.8+/-7.4 pg/min, than in SHR, from 9.9+/-1.7 to 17.0+/-3.2 pg/min. In WKY, renal pelvic administration of substance P at 0.8, 4, and 20 microg/mL increased ARNA 382+/-69, 750+/-233, and 783+/-124% second (area under the curve of afferent renal nerve activity versus time). In SHR, substance P at 0.8 to 20 microg/mL failed to increase ARNA. These findings demonstrate that the impaired afferent renal nerve activity response to increased renal pelvic pressure is related to decreased release of substance P and/or impaired activation of substance P receptors.

Afferent signaling and forebrain mechanisms in the behavioral control of extracellular fluid volume.

The body defends against reduced extracellular fluid volume both by activation of autonomic and endocrine reflexes and by mobilization of behavioral mechanisms. The behaviors that are required to correct an extracellular fluid deficit involve the ingestion of both water and sodium. It is reasonable to hypothesize that afferent neural input from both arterial and cardiopulmonary high pressure and volume receptors, and afferent humoral input in the form of ANG II, are important systemically-generated signals acting as afferent mediators of extracellular depletion-induced thirst and sodium appetite. Neural information from these signals has been shown to converge on forebrain structures located along the lamina terminalis where processing and integration of this input is likely to take place. This paper describes an analysis of the mechanisms of afferent signaling that accompanies a form of rapidly induced sodium appetite. Because volume and pressure-related input in concert with elevated activity of the renin-angiotensin system is likely to be important for generating this form of induced hypertonic sodium chloride and water intake, we have focused on the structures of the lamina terminalis, specifically the SFO, MnPO, and OVLT. Investigations that employ immunocytochemical methods for the detection of the early oncogene, c-fos, indicate that neurons in the lamina terminalis, as well as the SON and PVN, are activated by the composite of systemically derived signals necessary for producing thirst and sodium appetite. So far, there is no thorough understanding of how these visceral signals activate the neural substrates for these motivated behaviors. However, these studies, combining both functional and neuroanatomical approaches, provide a strategy for investigating the neurobiological basis of the behavioral and physiological control systems that maintain fluid balance and cardiovascular homeostasis. This paper describes an analysis of the mechanisms of afferent signaling that accompanies a form of rapidly induced sodium appetite. Because volume and pressure-related input, in concert with elevated activity of the renin-angiotensin system, is likely to be important for generating this form of induced hypertonic sodium chloride and water intake, we have focused on the structures of the lamina terminalis, specifically the SFO, MnPO, and OVLT. Investigations that employ immunocytochemical methods for the detection of the early oncogene, c-fos, indicate that neurons in the lamina terminalis, as well as the SON and PVN, are activated by the composite of systemically derived signals necessary for producing thirst and sodium appetite. So far, there is no thorough understanding of how these visceral sensory-related signals activate the neural substrates for these motivated behaviors.(ABSTRACT TRUNCATED AT 400 WORDS)