Potential regulatory role of inflammatory cells on local vascular smooth muscle tone

Autophagy Is Impaired in Neutrophils from Streptozotocin-Induced Diabetic Rats

We tested the hypothesis that changes reported on functions of neutrophils from streptozotocin-induced diabetic rats involve autophagy impairment. Wistar rats were rendered diabetic by streptozotocin injection (65 mg/kg, i.v.), and the measurements were carried out 2 weeks afterward. Neutrophils were collected through intraperitoneal cavity lavage after 4 h of i.p. oyster glycogen type 2 injection. Neutrophils cultured with PMA (20 nM) for 1 h were used for analysis of plasma membrane integrity, DNA fragmentation, and mitochondrial depolarization by flow cytometry; expression of Atg5, Atg14, Beclin1, LC3BII, and Rab9 by RT-PCR; the contents of caspase 3, LC3BII/LC3BI, and pS6 by western blotting; ATP content by fluorescence essay; reactive oxygen species production by chemiluminescence (Luminol), and autophagy by immunofluorescence tracking LC3B cleavage. Herein, neutrophils from diabetic rats had high DNA fragmentation, depolarization of mitochondrial membrane, low content of ATP, and high content of cleaved caspase 3 after PMA stimulation. Neutrophils from diabetic rats also had low expression of LC3B, failed to increase the expression of Rab9 and Atg14 induced by PMA stimulation. Neutrophils from diabetic animals also had low cleavage of LC3BI to LC3BII and do not present punctate structures that label autophagosomal membranes after stimulus. The changes of neutrophil function reported in diabetic rats do involve impaired autophagy. The suppression of autophagy in neutrophils from diabetic rats may be associated with the activation of the mTOR signaling as indicated by the high content of pS6.

Effects of anti-inflammatory drugs upon nitrate and myeloperoxidase levels in the mouse pleurisy induced by carrageenan

The effects of several drugs (terfenadine, bradykinin B2 receptor antagonists: HOE 140, NPC 17731, diacerein, indomethacin, meloxicam, nabumetone, and dexamethasone) upon myeloperoxidase and nitrate levels were analyzed in an inflammation model characterized by biphasic peaks (4 and 48 h) of cell migration and of fluid leakage. Myeloperoxidase levels were significantly higher only in the first phase (4 h; median and range; 537.5; 323.6-683.7 mU/ml; P < 0.01), whereas increased mean nitrate levels were detected in both phases (4 h: 19.0; 6.2-32 microM and 48 h: 13.7; 8.9-17.8 microM; P < 0.01). Enhancement of both cell migration and myeloperoxidase levels, 4 h after pleurisy induction, was effectively inhibited by all studied drugs. All of them, except diacerein also inhibited exudation. At this time, nabumetone and diacerein also significantly reduced nitrate levels (P < 0.01). Regarding the second phase (48 h), although dexamethasone, diacerein, and terfenadine decreased either cell migration or exudation, no drugs caused any change in the levels of nitrate. These results indicate that the degree of inhibition of the tested drugs upon the parameters studied do not match, suggesting that differences in these effects may certainly interfere with their efficacy.

Prolactin modulation of nitric oxide and TNF-alpha production by peripheral neutrophils in rats

It has been demonstrated that prolactin (PRL) is a potent immunomodulator that exerts stimulatory effects on physiological responses of immune cells. In the present research we have investigated whether PRL may influence nitric oxide (NO) and/or tumor necrosis factor-alpha (TNF-alpha) production in neutrophils obtained from inflammatory exudate of carrageenin-induced experimental pleurisy in the rat. In this acute model of inflammation the role of endogenous NO was evaluated using an inhibitor of NO-synthase, NG-nitro-L-arginine methyl ester (L-NAME). A treatment of animals with L-NAME (10 mg/kg s.c.) induced a reduction of volume and cell number of pleural exudate and a decrease of nitrite production (measured by the Griees reaction) by polymorphonuclear cells after 24 h of incubation, while D-NAME, the inactive isomer, was without effect. Neutrophils from ovine prolactin (oPRL) treated rats (5 mg/kg for 5 times s.c.) or from rats with a hyperprolactinaemia induced by pituitary gland graft produced higher amounts of NO both after 24 and 48 h of incubation. On the contrary, a clear reduction in the production of NO was found in neutrophils from rats treated with bromocriptine (BRC) (2 mg/kg s.c.), a dopamine D2-receptor agonist. TNF-alpha production (measured by MTT/cytotoxic assay) by neutrophils was markedly increased in PRL-treated or pituitary-grafted rats in comparison to controls, whereas BRC treatment reduced TNF-alpha production.

Endogenous nitric oxide increases prostaglandin biosynthesis in carrageenin rat paw oedema

The influence of endogenous nitric oxide (NO) on prostaglandin biosynthesis in rat carrageenin oedema was studied. Oedema formation and prostaglandin E2 generation in the inflamed paw were both increased by L- but not D-arginine and reduced by the NO synthase inhibitor, L-NG-nitro arginine methyl ester, and the NO scavenger, haemoglobin. Methylene blue, an inhibitor of the soluble guanylate cyclase, had no effect. These results suggest that endogenous NO modulates carrageenin oedema by increasing prostaglandin biosynthesis at the inflammatory site through a cGMP-independent mechanism.

A neutrophil-derived NO-synthase (NOS) inhibitor

In the present work we have demonstrated that the low NOS activity of circulating blood neutrophils is related to an endogenous inhibitory factor. This factor inhibits constitutive NOS (cNOS) of cerebellum and inducible NOS (iNOS) of macrophages in a concentration-dependent manner. Boiling only partially diminished its activity. The inhibition of cNOS was specific, since to some degree NADPH (0.5-4 mM) and more effectively L-arginine (0.1-1 mM), but not D-arginine, reversed the inhibition.

Effect of SCH 39166, a novel dopamine D1 receptor antagonist, on [3H]acetylcholine release in rat striatal slices

SCH 39166 is a novel and selective dopamine D1 receptor antagonist. It has been reported to have potential antipsychotic properties and reduced extrapyramidal side-effect liabilities (EPS). The current studies investigated the pharmacological effects of SCH 39166 on striatal cholinergic function in order to further characterize its dopamine D1 receptor selectivity and to address its EPS liability. Electrically stimulated [3H]acetylcholine (ACh) release from rat striatal slices was measured and comparisons were made between SCH 39166, SCH 23390, (-)-sulpiride, haloperidol or apomorphine on their effect on [3H]ACh release. Results indicated that apomorphine inhibited [3H]ACh release from striatal slices (IC50 = 0.31 microM). (-)-Sulpiride and haloperidol completely reversed the inhibition of [3H]ACh release seen with apomorphine. In contrast, SCH 39166, as well as, SCH 23390 did not reverse the inhibition of [3H]ACh release induced by apomorphine. These findings indicate that dopamine D2 receptors are primarily involved in modulation of [3H]ACh release. Furthermore, selective dopamine D1 receptor antagonists, such as SCH 39166, are ineffective in modulating striatal [3H]ACh release, suggesting that striatal cholinergic hyperactivity and possibly EPS will not be a consequence of dopamine D1 receptor blockade.

Modulation of acute inflammation by endogenous nitric oxide

The role of endogenous nitric oxide (NO) in acute inflammation was investigated using two inhibitors of NO synthase (NG-nitro-L-arginine methyl ester(L-NAME) and NG-monomethyl-L-arginine (L-NMMA)) as well as L- or D-arginine. The effect of test compounds was studied on the carrageenin-induced increase in vascular permeability in rat skin and in dextran- and carrageenin-induced paw oedema. Both L-NAME and L-NMMA dose dependently inhibited the increase in vascular permeability and oedema formation. L- but not D-arginine increased these inflammatory responses and reversed the inhibitory effects of L-NAME and L-NMMA. In dexamethasone-treated rats L-arginine enhanced the dextran-induced oedema and the early phase of carrageenin-induced oedema but did not modify the inhibition by dexamethasone of the late phase of carrageenin-induced oedema. These results suggest that endogenous NO is released at the site of acute inflammation and modulates oedema formation. Depending on the time course or on the type of inflammation, NO may be predominantly generated by the constitutive or by the inducible NO synthase.

Induction of nitric oxide synthase in rat peritoneal neutrophils and its inhibition by dexamethasone

Rat peritoneal polymorphonuclear leukocytes (PMN) elicited with oyster glycogen contain a Ca(2+)-independent nitric oxide (NO) synthase which is induced in vivo in a time-dependent manner. When washed PMN containing low levels of enzyme activity were cultured ex vivo further expression of NO synthase was observed. This was inhibited by cycloheximide indicating that de novo synthesis of the enzyme occurred during the ex vivo incubation. Enzyme activity was enhanced by interferon (IFN)-gamma, but not by tumor necrosis factor (TNF)-alpha when added ex vivo. However, IFN-gamma and TNF-alpha synergized to increase further the expression of NO synthase. Treatment of rats with dexamethasone inhibited the induction of NO synthase in elicited PMN. This treatment reduced the accumulation of PMN by approximately 30%, without affecting cell viability. Dexamethasone also inhibited the induction of the NO synthase ex vivo in a concentration-dependent manner. Furthermore, the enhanced enzyme activity following treatment of PMN with cytokines was also inhibited by dexamethasone. Once induced, dexamethasone did not affect enzyme activity. These data indicate that PMN elicited in the rat peritoneum with oyster glycogen express an NO synthase in vivo and ex vivo. The induction of the enzyme can be further stimulated ex vivo with IFN-gamma and TNF-alpha and inhibited by dexamethasone. The inhibition of the induction of NO synthase in the PMN by dexamethasone may contribute to the anti-inflammatory activity of this and other glucocorticoids.