Interleukin-1beta-induced, nitric oxide-dependent and -independent inhibition of vascular smooth muscle contraction

Role of Perivascular Adipose Tissue in Health and Disease

Perivascular adipose tissue (PVAT) is cushion of fat tissue surrounding blood vessels, which is phenotypically different from other adipose tissue depots. PVAT is composed of adipocytes and stromal vascular fraction, constituted by different populations of immune cells, endothelial cells, and adipose-derived stromal cells. It expresses and releases an important number of vasoactive factors with paracrine effects on vascular structure and function. In healthy individuals, these factors elicit a net anticontractile and anti-inflammatory paracrine effect aimed at meeting hemodynamic and metabolic demands of specific organs and regions of the body. Pathophysiological situations, such as obesity, diabetes or hypertension, induce changes in its amount and in the expression pattern of vasoactive factors leading to a PVAT dysfunction in which the beneficial paracrine influence of PVAT is shifted to a pro-oxidant, proinflammatory, contractile, and trophic environment leading to functional and structural cardiovascular alterations and cardiovascular disease. Many different PVATs surrounding a variety of blood vessels have been described and exhibit regional differences. Both protective and deleterious influence of PVAT differs regionally depending on the specific vascular bed contributing to variations in the susceptibility of arteries and veins to vascular disease. PVAT therefore, might represent a novel target for pharmacological intervention in cardiovascular disease. © 2018 American Physiological Society. Compr Physiol 8:23-59, 2018.

Cardiovascular autonomic regulation, inflammation and pain in rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is a chronic inflammatory condition characterised by reduced heart rate variability (HRV) of unknown cause. We tested the hypothesis that low HRV, indicative of cardiac autonomic cardiovascular dysfunction, was associated with systemic inflammation and pain. Given the high prevalence of hypertension (HTN) in RA, a condition itself associated with low HRV, we also assessed whether the presence of hypertension further reduced HRV in RA.

Methods

In RA-normotensive (n = 13), RA-HTN (n = 17), normotensive controls (NC; n = 17) and HTN (n = 16) controls, blood pressure and heart rate were recorded. Time and frequency domain measures of HRV along with serological markers of inflammation (high sensitivity C-reactive protein [hs-CRP], tumour necrosis factor-α [TNF-α] and interleukins [IL]) were determined. Reported pain was assessed using a visual analogue scale.

Results

Time (rMSSD, pNN50%) and frequency (high frequency power, low frequency power, total power) domain measures of HRV were lower in the RA, RA-HTN and HTN groups, compared to NC (p = 0.001). However, no significant differences in HRV were noted between the RA, RA-HTN and HTN groups. Inverse associations were found between time and frequency measures of HRV and inflammatory cytokines (IL-6 and IL-10), but were not independent after multivariable analysis. hs-CRP and pain were independently and inversely associated with time domain (rMMSD, pNN50%) parameters of HRV.

Conclusions

These findings suggest that lower HRV is associated with increased inflammation and independently associated with increased reported pain, but not compounded by the presence of HTN in patients with RA.

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Rheumatoid arthritis (RA) is a chronic inflammatory condition accompanied by low heart rate variability (HRV).

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Important autonomic-immune interactions are suggested, but have not been thoroughly examined in RA.

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We show that low HRV in RA is associated with increased serum inflammatory cytokine levels and patient-reported pain.

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In our patients with RA, reductions in HRV were not compounded by the presence of hypertension.

Effects of interleukin-1β on vascular reactivity after lipopolysaccharide-induced endotoxic shock in rabbits and its relationship with PKC and Rho kinase

Calcium desensitization plays a critical role in the occurrence of vascular hyporeactivity after shock. Interleukin (IL)-1β participates in the regulation of vascular reactivity via both nitric oxide (NO)-dependent and NO-independent mechanisms. However, the specific NO-independent pathway remains to be established. The issue of whether IL-1β modulates vascular reactivity via regulation of calcium sensitivity in the NO-independent mechanism is unclear. In the current study, effects of IL-1β on vascular calcium sensitivity and its relationship with PKC and Rho kinase were investigated in vivo and in vitro using a rabbit model of lipopolysaccharide (LPS)-induced endotoxic shock and superior mesenteric arteries (SMAs), respectively. The calcium sensitivity profile of SMAs displayed a biphasic change after LPS-induced endotoxic shock (significant increase at 0.5 hour and 1 hour after LPS administration and marked decrease after 2 hours) and was negatively related to changes in serum IL-1β. The IL-1 receptor antagonist, IL-1ra (4 μg/mL), partly reversed LPS-induced calcium desensitization. In vitro incubation with IL-1β (50-200 ng/mL) reduced the calcium sensitivity of SMAs and suppressed the activities of Rho kinase and PKC and the phosphorylation of 20-kDa myosin light chain. These effects of IL-1β were shown to be regulated by the PKC agonist, phorbol 12-myristate 13-acetate, and Rho kinase agonist and antagonist, angiotensin II, and Y-27632, respectively. Our results collectively suggest that IL-1β participates in vascular hyporeactivity after endotoxic shock via regulation of vascular calcium sensitivity. Moreover, this regulatory effect of IL-1β seems closely related to downregulation of the activities of PKC and Rho kinase.

Role of cytokines in altitude-associated preeclampsia

BACKGROUND: Preeclampsia (PE) is more common at high than low altitude and contributes to the altitude-related decline in birth weight. Since inflammatory markers are implicated in PE, we asked if such markers differed in PE vs. normotensive pregnant (NORM) women residing at high altitude (3600-4100 m), and were related to uterine artery blood flow (UA BF) or fetal growth. METHODS: Subjects were 33 Andean pregnant residents of Bolivia, comprising six with early-onset PE (≤ 34 wk), 12 with late-onset PE (> 34 wk), and 15 gestational-age matched NORM. Maternal pro- and anti-inflammatory cytokines were measured using a multiplex bead-based assay and UA BF by Doppler ultrasound. RESULTS: PE compared to NORM women had higher levels of the pro-inflammatory cytokines IL-6 and IL-8 as well as higher levels of the anti-inflammatory cytokine IL-1ra, but only IL-6 levels were higher when gestational age was controlled. Women with early- vs. late-onset PE had higher TNFα levels, and higher IL-6 was negatively correlated with birth weight in all women at ≤ 34 wk. We suggest that pro-inflammatory factors influence both the timing and severity of PE at high altitude.

Do cytokines contribute to the Andean-associated protection from reduced fetal growth at high altitude?

Pro- versus anti-inflammatory cytokine balance is important for successful pregnancy. Chronic hypoxia alters cytokine levels and increases the frequency of fetal growth restriction (FGR). Multigenerational Andean (AND) versus shorter duration European (EUR) high-altitude (HA) residents are protected from altitude-associated FGR. To address whether ancestry group differences in cytokine levels were involved, we conducted serial studies in 56 low-altitude ([LA]; 400 m; n = 29 AND and n = 27 EUR) and 42 HA residents (3600-4100 m; n = 19 ANDs and n = 23 EURs). Pregnancy raised pro- (interleukin 1β [IL-1β]) and anti- (IL-10) inflammatory cytokines and HA lowered IL-6 and tumor necrosis factor-α (TNF-α) near term. There were no ancestry group differences in cytokine levels at any time, but HA reduced IL-1β in ANDs only near term. Higher IL-1β levels correlated with uterine artery (UA) blood flow at 20 weeks in ANDs at HA, suggesting that IL-1β may play a role in AND protection from altitude-associated reductions in fetal growth.

Modulation of cerebral vascular tone by activated glia: involvement of nitric oxide

The ability of activated glia to affect cerebral vascular tone has been evaluated using an in vitro experimental system in which basilar arteries were incubated with glial cultures activated by treatment with lipopolysaccharide (LPS). Vascular tone was measured with an isometric myograph. Contraction in response to high KCl and serotonin was reduced in arteries co-incubated for 24 h with LPS-activated glia, whereas the response to acetylcholine was not modified. The reduced contraction was prevented when the nitric oxide synthase (NOS) inhibitor L-N-nitro-arginine (L-NNA) was added throughout the whole incubation time (activation of glial cells with LPS + co-incubation of glial cells with cerebral arteries). Under these conditions, nitrite levels were drastically reduced. A reduced contraction to KCl was also observed after treatment of the cerebral vessel with sodium nitroprusside. In contrast, L-NNA added to the vessel did not modify the response to contracting stimuli and the expression of endothelial NOS was not modified in cerebral arteries pre-incubated with activated glia. These results suggest that activated glia, which finds an in vivo correlate in several neuropathological conditions, can contribute to changes of vascular tone by modifying the levels of nitric oxide (NO) to which the vessel is exposed.

Synthesis of immune modulators by smooth muscles

The primary function of smooth muscle cells is to contract and alter the stiffness or diameter of hollow organs such as blood vessels, the airways and the gastrointestinal and urogenital tracts. In addition to purely structural functions, smooth muscle cells may play important metabolic roles, particularly in various inflammatory responses. In cell culture, these cells have been shown to be metabolically dynamic, synthesizing and secreting extracellular matrix proteins, glycosaminoglycans and a wide variety of cell-cell signaling proteins, such as interleukins, chemokines and peptide growth factors. Secreted cell signaling proteins participate in the inflammatory response of smooth muscle-containing organs, and some can also stimulate smooth muscle migration, proliferation and contraction. The cellular signaling pathways controlling synthesis of these signaling proteins are similar to those used by cells mediating innate immunity and may contribute to pathogenesis of diverse diseases including atherosclerosis, asthma, inflammatory bowel diseases and preterm labor. Appreciating the role of smooth muscle cells in these diseases may lead to better understanding of the beneficial effects of anti-inflammatory drugs as well as identification of new targets for anti-inflammatory therapy.

Enhancement of endotoxin-induced vascular hyporeactivity to phenylephrine in the thoracic aortas of Mg-deficient rats ex vivo

Since endotoxin lethality is enhanced by Mg deficiency in animals, we determined whether endotoxin-induced vascular hyporeactivity to phenylephrine (PE) is enhanced in Mg-deficient rats. Normal and Mg-deficient adult male Wistar rats were injected with Escherichia coli 011: B4 lipopolysaccharide (1 or 5 mg/kg, i.p.). Six h later, rings prepared from their thoracic aortas showed severe hyporeactivity to PE. This was more pronounced in the Mg-deficient rats, and was reversed by in vitro treatment with a highly selective inducible nitric oxide (NO) synthase inhibitor, 1400 W, or a highly selective soluble guanylyl cyclase inhibitor, ODQ. However, reversal required high doses of both inhibitors in Mg-deficient rats. Endotoxemia for 6 h was associated with elevated serum interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha levels, and strong TNF receptor mRNA expression in the abdominal aortas, which were significantly greater in the Mg-deficient rats. Treatment of the thoracic aortas, isolated from control and Mg-deficient rats before endotoxic challenge, with IL-1beta or TNF-alpha for 6 h in vitro caused hyporeactivity to PE, but its severity did not differ significantly between the two groups. These results suggest that high serum IL-1beta and TNF-alpha levels, and increased TNF receptor production in the vascular tissue, contribute to vascular hyporeactivity to PE in endotoxemia, and to its enhancement in Mg-deficient rats, via NO/cGMP signaling.

Organ culture as a useful method for studying the biology of blood vessels and other smooth muscle tissues

The benefit of organ culture is to retain the original structural relationship between various cell species and their interactions and enable us to study the long-term effects of exogenous stimuli. Organ culture methods have been used especially in the studies of the proliferative vascular diseases, such as atherosclerosis and restenosis. We describe here that organ culture is a useful in vitro method to study the biology of vascular and other smooth muscle organs.

[High throughput pharmacology for drug discovery]

High Throughput Screening (HTS) now plays an important role in the discovery of new lead compounds for novel therapeutic targets. The advantage of HTS over the conventional method, now termed as Low Throughput Screening (LTS), is that valuable compounds can be selected rapidly from a large number of samples with minimal human involvement. In spite of the growing awareness of HTS, the importance of the LTS in the drug discovery and development is still not changed. Advances in pharmacogenomics will also provide us many pharmacological targets, and thus increase the number of compounds that should be assayed by HTS and LTS. In this review, we will first describe the outline of HTS. We will next describe new approaches to develop and brush up the LTS: 1) screening method of drugs acting on ion channels by voltage-sensitive fluorescent dye, 2) functional assay method using reconstituted smooth muscle fiber, and 3) organ culture method as a useful model of vascular proliferative disease. These approaches, which work cooperatively with HTS, will contribute greatly to the development of new drugs.

Role of nitric oxide in the cerebrovascular and thermoregulatory response to interleukin-1 beta

Central administration of interleukin-1 beta (IL-1 beta) increases cerebral blood flow (CBF) and body temperature, in part, through the production of prostaglandins. In previous studies, the temporal relationship between these effects of IL-1 beta have not been measured. In this study, we hypothesized that the increase in CBF occurs before any change in brain or body temperature and that the cerebrovascular and thermoregulatory effects of IL-1 beta would be attenuated by inhibiting the production of nitric oxide (NO). Adult male rats received 100 ng intracerebroventricular (icv) injection of IL-1 beta, and cortical CBF (cCBF) was measured by laser-Doppler in the contralateral cerebral cortex. A central injection of IL-1 beta caused a rapid increase in cCBF to 133 +/- 12% of baseline within 15 min and to an average of 137 +/- 12% for the remainder of the 3-h experiment. Brain and rectal temperature increased by 0.4 +/- 0.2 and 0.5 +/- 0.2 degrees C, but not until 45 min after IL-1 beta administration. Pretreatment with N(omega)-nitro-L-arginine methyl ester (L-NAME; 5 mg/kg iv) completely prevented the changes in cCBF and brain and rectal temperature induced by IL-1 beta. L-Arginine (150 mg/kg iv) partially reversed the effects of L-NAME and resulted in increases in both cCBF and temperature. These findings suggest that the vasodilatory effects of IL-1 beta in the cerebral vasculature are independent of temperature and that NO plays a major role in both the cerebrovascular and thermoregulatory effects of centrally administered IL-1 beta.

Possible involvement of K+ channel opening to the interleukin-1 beta-induced inhibition of vascular smooth muscle contraction

We have previously shown that interleukin-1 beta relaxes vascular smooth muscle by the NO-dependent and independent mechanisms (Takizawa et al.: Eur. J. Pharmacol. 330: 143-150, 1997). In this study, we investigated the mechanism of NO-independent relaxation. Treatment of the rat aorta with interleukin-1 beta for 24 hr inhibited the high-K+ induced contraction by decreasing cytosolic Ca2+ level ([Ca2+]i). The relationship between [Ca2+]i and tension in intact muscle and the pCa-tension curves in permeabilized muscle suggested that Ca2+ sensitivity of contractile element was not changed after the interleukin-1 beta-treatment. After a treatment with interleukin-1 beta for 24 hr, contractile effects of phenylephrine (1 microM-10 microM) were markedly inhibited in the presence of L-NMMA (100 microM) applied to inhibit NO synthesis. A blocker of ATP-sensitive K+ channel, glibenclamide (1 microM), partially recovered the interleukin-1 beta-induced inhibition. In contrast, a blocker of Ca(2+)-activated K+ channel, charybdotoxin (0.1 microM), was ineffective. These results suggest that membrane hyperpolarization due to activation of ATP-sensitive K+ channels may partly be responsible for the NO-independent mechanism of interleukin-1 beta-induced inhibition of vascular smooth muscle contraction.

Inducible nitric oxide synthase and atherosclerosis

Nitric oxide (NO) synthase induction in vascular smooth muscle cells may play a role in local vascular injury associated with atherosclerosis or postangioplasty restenosis by inhibiting smooth muscle cell proliferation and contraction, as well as by preventing leukocyte and platelet adhesion. The expression of inducible NO synthase is increased in balloon-injured arteries of experimental animals or in human atherosclerotic lesions. Replacement therapy with NO donors or NO synthase gene transfer may improve the clinical course of atherosclerosis or restenosis.