Rocco Cirillo

Effect of ricinoleic acid in acute and subchronic experimental models of inflammation

Observational studies indicate that topical application of ricinoleic acid (RA), the main component of castor oil, exerts remarkable analgesic and anti-inflammatory effects. Pharmacological characterization has shown similarities between the effects of RA and those of capsaicin, suggesting a potential interaction of this drug on sensory neuropeptide-mediated neurogenic inflammation. The aim of this study was to assess RA anti-inflammatory activities in comparison with capsaicin in several models of acute and subchronic inflammation. The acute inflammation was induced by intradermal injection of carrageenan in the mouse or by histamine in the guinea-pig eyelid. In either experiment, the extent of the oedema thickness was measured. Subchronic oedema was induced by complete Freunds adjuvant injection in the ventral right paw of mice. Tissue substance P (SP) was measured in the carrageenan experiments by radioimmunoassay (RIA). It was found that the acute topical application of RA (0.9 mg/mouse) or capsaicin (0.09 mg/mouse) significantly increased the mouse paw oedema induced by carrageenan, while an 8-day repeated topical treatment with the same doses of both compounds resulted in a marked inhibition of carrageenan-induced paw oedema matched by a reduction in SP tissue levels. Similar effects were found against histamine-induced eyelid oedema in guinea-pigs after acute or repeated application of RA or capsaicin. RA and capsaicin given for 1-3 weeks reduced the established oedema induced by Freunds adjuvant, a subchronic model of inflammation, particularly if given by the intradermal route. Either in mouse paw or in guinea-pig eyelid, capsaicin but not RA by itself produced a slight hyperemia and activation of a behavioural response (e.g. scratching of the eyelids). On the basis of the present results, RA may be seen as a new capsaicin-like, non-pungent anti-inflammatory agent suitable for peripheral application.

The effect of transdermal 17-β-estradiol on glucose metabolism of postmenopausal women is evident during the oral but not the intravenous glucose administration

OBJECTIVESnTo evaluate the effect of transdermal 17-beta-estradiol (50 micrograms/day) on glucose metabolism of postmenopausal women.nnnSTUDY DESIGNnA frequently sampled intravenous glucose tolerance test (FSIGT), to calculate insulin sensitivity (SI) and peripheral glucose utilization independent of insulin (SG), and an oral glucose tolerance test (75 g; OGTT), were performed in nine postmenopausal women prior to, and after 2 months of, treatment.nnnRESULTSnEstradiol decreased insulin and increased the C-peptide/insulin ratio both during fasting (P < 0.02) and OGTT (insulin levels, P < 0.01; C-peptide/insulin ratio, P < 0.05), but not FSIGT. Glucose levels, C-peptide levels, SI and SG were not affected.nnnCONCLUSIONSnIn spite of unmodified SI, the reduction of insulin levels and the increase of the C-peptide/insulin ratio, observed during fasting and OGTT, support a beneficial effect of estradiol on glucose metabolism. This effect probably requires the interplay of estradiol with gastrointestinal factors.

Pro- and anti-inflammatory actions of ricinoleic acid: similarities and differences with capsaicin

Abstract. We have investigated the pro- and anti-inflammatory effects of ricinoleic acid (RA), the main active principle of castor oil, in an experimental model of blepharitis induced by intradermal injection of carrageenan in the guinea-pig eyelid and its possible capsaicin-like mode of action on acutely dissociated rat dorsal root ganglia (DRG) neurons in vitro.Topical treatment with RA (10–100xa0mg/guinea-pig) or capsaicin (1–10xa0mg/guinea-pig) caused eyelid reddening and oedema. At lower doses (0.3–3xa0mg/guinea-pig and 0.009–0.09xa0mg/guinea-pig for RA and capsaicin, respectively) both drugs significantly potentiated the eyelid oedema induced by carrageenan. The tachykinin NK1 receptor antagonist FK 888 (0.59xa0mg/kg s.c.) abolished the potentiation of carrageenan-induced eyelid oedema induced by either RA or capsaicin. The neutral endopeptidase inhibitor, thiorphan (1.3xa0mg/kg i.v.) significantly enhanced the potentiation of carrageenan-induced eyelid oedema produced by RA. This potentiating effect was abolished by FK 888. Repeated (8xa0days) topical application of RA (0.9xa0mg/guinea-pig) or capsaicin (0.09xa0mg/guinea-pig) inhibited the carrageenan-induced eyelid oedema. This anti-inflammatory effect was accompanied by a reduction (75%–80% of SP and 46%–51% of NKA) in tachykinin content of the eyelids, as determined by radioimmunoassay. In dissociated rat DRG neurons, RA (0.1xa0mM for 5xa0min) significantly inhibited the inward currents induced by application of capsaicin (1xa0µM) and/or low pH (5.8), without inducing any currents by itself or changing voltage-dependent currents. Moreover, after 24-h incubation, RA (0.1xa0mM) significantly decreased the capsaicin (1xa0µM)-induced calcitonin gene-related peptide (CGRP) release from rat DRG neurons, whereas acute drug superfusion did not evoke CGRP release by itself.Summarizing, RA possesses capsaicin-like dual pro-inflammatory and anti-inflammatory properties which are observed upon acute and repeated application, respectively. However, unlike capsaicin, RA does not induce inward current in DRG neurons and it is devoid of algesic properties in vivo.

Antinociceptive activity of ricinoleic acid, a capsaicin-like compound devoid of pungent properties

The antinociceptive effect of ricinoleic acid ([R-(Z)]-12-hydroxy-9-octadecenoic acid) in comparison with capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide) has been investigated in several in vivo tests. Acute topical application of capsaicin, but not ricinoleic acid, produced by itself an hyperalgesic effect detected as a decrease in paw withdrawal latency in response to a painful (heat) stimulus in mice. Capsaicin, but not ricinoleic acid at any dose tested, showed an irritant effect in the wiping test in guinea pig conjunctiva after local application and in the paw licking test in mice after intradermal injection. Whereas acute application of ricinoleic acid or capsaicin decreased paw withdrawal latency to heat in the presence of a pre-existing inflammation (injection of carrageenan in the mouse paw), the repeated local treatment for 8 days with either compounds markedly increased paw withdrawal latency. In a chronic model of inflammation (complete Freunds adjuvant arthritis in mice), the repeated topical and intradermal treatments with both ricinoleic acid and capsaicin increased paw withdrawal latency to heat, the antinociceptive effect of ricinoleic acid being more persistent than that of capsaicin. Antinociceptive effect of 8 days of treatment with ricinoleic acid and capsaicin was observed in acetic acid-induced writhing in mice, capsaicin-induced foot licking in mice and capsaicin-induced wiping movements in guinea pig conjunctiva. A decrease of substance P tissue levels in the mouse paw was found after repeated treatment with ricinoleic acid. In conclusion, ricinoleic acid seems to be a new antinociceptive agent lacking the pungent and acute hyperalgesic properties of capsaicin.

Is the imbalance between thrombin and plasmin activity in diabetes related to the behaviour of antiplasmin activity

The aim of this study was to evaluate the balance between thrombin and plasmin activity in a group of 79 diabetic patients (IDDM and NIDDM). For this purpose we determined fibrinopeptide A (FPA) and B beta 15-42, specific products of thrombin and plasmin activity. Moreover we investigated the behaviour of antithrombin III and alpha 2 antiplasmin, important inhibitors of blood coagulation and fibrinolysis. Results show an increase both in FPA and B beta 15-42 in IDDM and NIDDM patients when compared to healthy controls. However the ratio between B beta 15-42 and FPA was lower than in controls indicating an imbalance between thrombin and plasmin activity. Antithrombin III levels were not different from the controls and no correlation was found with Hb A1c. alpha 2 antiplasmin was found to be higher in IDDM when compared both with NIDDM and controls. A non linear correlation was found between Hb A1c and alpha 2 AP in both diabetic groups. We conclude that the imbalance between thrombin and plasmin activity may have a role in determining fibrin deposition. These subclinical abnormalities, unrelated to vascular complications and duration of the disease, may progressively contribute to the development of the vascular complications in diabetes.

“Falsely Increased” Bβ15–42 Levels in Diabetes

We read with interest the article by Small et al. (1), who found high levels of tissue plasminogen activator inhibitor in a group of diabetic patients. However, they did not find any relationship between the levels of tissue plasminogen inhibitor and the fibrinolytic activity, the latter being expressed by both the fibrin-plate lysis zone test and the levels of Bp15_42 antigen, which were found to be normal. We determined the Bp15_42 antigen, an early product of plasmin activity on fibrinogen/fibrin (2), by using a radioimmunoassay technique (IMCO, Stockholm). Two groups of diabetic patients were tested: insulin-dependent diabetes mellitus (IDDM; n = 29, 17 males, 12 females; mean age 23 yr, range 12-47 yr) and noninsulin-dependent diabetes mellitus (NIDDM; n = 50, 32 males, 18 females; mean age 57 yr, range 31-83 yr). The Mann-Whitney U test was used for statistical evaluation of the data. The results are expressed as medians and ranges. We found a significant increase in Bp15_42 values in both IDDM (12.7, 5.7-30.1 ng/ml; P < 0.001) and NIDDM (12.0, 5.4-26.4 ng/ml; P < 0.004) patients compared with 42 control subjects (10.1, 5.8-13.0 ng/ml). Moreover, we concomitantly measured fibrinopeptide A (FPA) by a radioimmunoassay method (Mallinckrodt, Paris, KY), a sensitive indicator of thrombin activity in vivo (3), which turned out to be significantly elevated in both groups (IDDM: 6.7, 1.4-40.1 ng/ml, P < 0.001; NIDDM: 6.6, 1.6-32.5 ng/ml, P < 0.001) compared with control subjects (2.3, 1.2-4.6 ng/ml). However, when we computed the ratio between Bp15_42 and FPA to obtain an index of relative plasmin to thrombin action on fibrinogen/fibrin, we found a significantly lower Bp15_42-FPA ratio in both groups of patients (IDDM: 1.85, 0.4-10.0 ng/ml, P < 0.001; NIDDM: 1.65, 0.3-8.2 ng/ml, P < 0.001) with respect to control subjects (3.85, 1.8-12.6 ng/ml). We feel that an imbalance between blood coagulation and fibrinolysis does exist in diabetes, and the increased fibrinolytic activity in vivo does not appear to sufficiently counterbalance the blood coagulation activity. This may be important because localized deposition of fibrin is dependent on an imbalance between its rate of formation and dissolution (4). The high plasminogen activator inhibitor activity found by Small et al. could have had a role in limiting the fibrinolytic activity that caused it to appear falsely normal. We therefore conclude that a correct evaluation of the fibrinolytic system in response to its inhibitors and the blood coagulation activity should take into account both the inhibitors of tissue plasminogen activators and the thrombin activity, measured by means of FPA.