Atorvastatin inhibits inflammatory hypernociception

Evaluation of the Antinociceptive Action of Simvastatin in Mice

Introduction: Statins are well-established agents for dyslipidemia and have successfully been used for the prevention of coronary artery diseases for a long time; this is attributed not only to their lipid-lowering action but also to their pleiotropic actions. Recently many pleiotropic actions of statins have been explored, but very few studies were done to explore statins' antinociceptive action; therefore, the current study was planned to evaluate the antinociceptive activity of Simvastatin in different pain models in mice.

Materials and Methods: Antinociceptive activity of Simvastatin was evaluated by using Eddy's hot plate method (central analgesic model), acetic acid-induced writhing method (peripheral analgesic model), and biphasic formalin-induced paw licking method. Twenty-four mice were divided into four groups (n = 6 in each): Vehicle control group, simvastatin 5mg/kg, simvastatin 20mg/kg, and positive control group.

Results: In the hot plate method, as compared to the vehicle control group, Simvastatin 20mg/kg group showed a significant rise in the reaction time to the corresponding time interval (p<0.001). While the simvastatin 5mg/kg group did not show any significant analgesic activity in the hot plate test. In the acetic acid writhing method, both test groups show a significant delay in the onset of writhing and a decrease in the number of writhes as compared to the vehicle control group (P<0.001). While in the formalin test, both groups show dose-dependent analgesic activity in both the early and late phases.

Conclusion: Simvastatin exhibits analgesic activity in both central as well as peripheral models of analgesia, but central analgesia shows only at higher concentrations. Similarly, it inhibits inflammatory pain more predominantly than neurogenic, and hence simvastatin can be used in inflammatory conditions like rheumatoid arthritis and osteoarthritis particularly when there is coexisting dyslipidemia.

Standardized study of atorvastatin possible osteoarthritis disease-modifying effect in a rat model of osteoarthritis

We studied the osteoarthritis (OA)-modifying effects of atorvastatin in an experimental OA rat model and possible underlining mechanisms. We used 62 adult male Sprague-Dawley rats (250-300 g): 32 rats were used to assess the effects of atorvastatin on surgically induced OA in the knee, and 30 rats were used to assess the potential inflammatory effects of carrageenan-induced paw edema. In the OA model, joint stiffness was assessed by measuring the knee extension angle, and pathological changes in the OA knee joint were determined by histological examination and the measurement of serum biochemical markers, including interleukin-1β (IL-1β), matrix metalloproteinase-13 (MMP-13), and reduced glutathione (GSH). In the carrageenan-induced paw edema model, both paw thickness and pain threshold were assessed in different groups. Atorvastatin significantly improved joint stiffness, pathological changes, a significant mitigation of the higher MMP-13 and IL-1β, and a significant increase of reduced GSH in OA rats. Additionally, atorvastatin significantly improved both paw thickness and pain threshold in animals. Atorvastatin is a potential OA-modifying drug that warrants further clinical investigation.

Drug-specific and dosage effects of statins and the risk of cancer: a population-based cohort study in South Korea

This study aimed to investigate whether the drug-specific and dosage effects of statin use were associated with a lower risk of cancer in adults in South Korea. We evaluated the adult population registered in the 2010 sample cohort database of South Korea. Subjects were divided into the statin group (those who had been prescribed continuous oral statin over 1 year) and the control group (those who had never been prescribed statin from 2010 to 2016). In total, 687 396 individuals were included in the analysis [statin group, 53 592 (7.8%); control group, 633 804 (92.2%)]. In a multivariable Cox model, the hazard of cancer in the statin group was 5% lower than that in the control group [hazard ratio, 0.95; 95% confidence interval (CI), 0.91-0.98; P = 0.004]. Additionally, the hazard of cancer in patients receiving moderate- and high-intensity daily dosages of statin were 5% (hazard ratio, 0.95; 95% CI, 0.91-0.98; P = 0.005) and 9% (hazard ratio, 0.91; 95% CI, 0.83-0.99; P = 0.042) lower than that of the control group, respectively. The hazard of cancer in patients receiving atorvastatin was 6% (hazard ratio, 0.94; 95% CI, 0.90-0.98; P = 0.005) lower than that in the control group, while other types of statins showed no significant associations (all P > 0.05). Statin use was associated with a lower risk of cancer in South Korea. This association was stronger in patients receiving moderate and high daily dosages of statin and in patients receiving atorvastatin.

Prior Statin Therapy and Mortality After Extracorporeal Membrane Oxygenation Therapy: A Retrospective, Population-Based, Cohort Study

OBJECTIVE

To investigate whether prior statin therapy is associated with an improvement in mortality among patients who undergo extracorporeal membrane oxygenation (ECMO) therapy.

DESIGN

Retrospective, population-based, cohort study.

SETTING

Health records were obtained from the National Health Insurance Service database in South Korea.

PATIENTS

All adult patients (≥18 y) who underwent ECMO therapy in the intensive care unit between 2005 and 2018 were enrolled.

EXPOSURES

Statin users were defined as patients who were prescribed continuous oral statins ≥90 days before ECMO.

MEASUREMENTS AND MAIN RESULTS

The primary endpoint of this study was 90-day mortality. A total of 21,129 adult patients from 128 hospitals were included (4,737 [22.4%] statin users and 16,392 [77.6%] nonusers). After propensity score matching, 9,474 ECMO patients (4,737 in each group) were included in the final analysis. In the propensity-score-matched cohort, statin users exhibited lower 90-day mortality than did nonusers (58.6% [2,774/4,737] in statin users v 65.6% [3,106/4,737] in nonusers). In addition, on Cox regression, 90-day mortality in statin users was 14% less than that in nonusers (hazard ratio 0.86, 95% confidence interval 0.81-0.90; p < 0.001).

CONCLUSION

Among patients who underwent ECMO in South Korea, prior statin therapy was found to be associated with lower 90-day mortality rates after ECMO therapy. However, because this study had a retrospective design, future prospective trials are needed to confirm the findings.

Statin Therapy and the Risk of COVID-19: A Cohort Study of the National Health Insurance Service in South Korea

We aimed to investigate whether statin therapy is associated with the incidence of coronavirus disease 2019 (COVID-19) among the South Korean population. In addition, we examined whether statin therapy affects hospital mortality among COVID-19 patients. The National Health Insurance Service (NHIS)-COVID-19 database in South Korea was used for data extraction for this population-based cohort study. A total of 122,040 adult individuals, with 22,633 (18.5%) in the statin therapy group and 101,697 (91.5%) in the control group, were included in the analysis. Among them, 7780 (6.4%) individuals were diagnosed with COVID-19 and hospital mortality occurred in 251 (3.2%) COVID-19 cases. After propensity score matching, logistic regression analysis showed that the odds of developing COVID-19 were 35% lower in the statin therapy group than in the control group (odds ratio: 0.65, 95% confidence interval: 0.60 to 0.71; p < 0.001). Regarding hospital mortality among COVID-19 patients, the multivariable model indicated that there were no differences between the statin therapy and control groups (odds ratio: 0.74, 95% confidence interval: 0.52 to 1.05; p = 0.094). Statin therapy may have potential benefits for the prevention of COVID-19 in South Korea. However, we found that statin therapy does not affect the hospital mortality of patients who are diagnosed with COVID-19.

Prior statin therapy and 30-day mortality in South Korean patients with acute respiratory distress syndrome

BACKGROUND

The effect of prior statin therapy on mortality in patients with acute respiratory distress syndrome (ARDS) remains controversial. This study aimed to investigate whether prior statin therapy was associated with lower 30-day mortality compared to non-statin use.

METHODS

This population-based cohort study used nationwide data procured from the National Health Insurance service in South Korea, and included all the adult patients admitted to a hospital for ARDS treatment between January 1, 2013 and December 31, 2017.

RESULTS

In total, 14,600 patients with ARDS were included: 4,319 were statin users and 10,281 were non-statin users. After propensity score matching, 6,046 patients with ARDS (3,023 patients in each group) were included in the analysis. The 30-day mortality of statin users was 44.4% (1,331 of 3,023), while that of non-statin users was 45.2% (1,331 of 3,023). On Cox regression analysis in the propensity score matched cohort, 30-day mortality was not significantly associated with statin use compared to non-statin use (hazard ratio: 0.95, 95% confidence interval: 0.88 to 1.02; P = .165). On Kaplan-Meier estimation, the median survival time in statin users was 45 days (95% CI: 39 to 50), while that in non-statin users was 42 days (95% CI: 37 to 47) after propensity score matching, and there was no statistical difference with the log-rank test (P = .215).

CONCLUSION

This population-based cohort study in South Korea showed that prior statin therapy was not significantly associated with 30-day mortality in patients with ARDS. Our findings should be confirmed in future prospective studies.

Comparison of the Physical Characteristics and Behavior in ABC Transporter A1, A7 or Apolipoprotein E Knockout Mice with Lipid Transport Dysfunction

The physical characteristics and behavior of the ATP-binding cassette (ABC) A1, A7, and apolipoprotein (apo) E knockout (KO) mice with lipid transport dysfunction were investigated. These KO mice exhibited adequate growth, and their body masses increased steadily. No remarkable changes were observed in their blood pressure and heart rate. However, there was a slight increase in the heart rate of the ABCA7 KO mice compared with that of the wild-type (WT) mice. ABCA1 and apoE KO mice showed hypo- and hyper-cholesterol concentrations in the plasma, respectively. With regard to the cerebrum, however, the weight of the ABCA1 KO mice was lighter than those of the other genotypes. Furthermore, the cholesterol, triglyceride and phospholipid concentrations, and fatty acid composition were generally similar. Compared with the WT mice, ABCA1 KO mice stayed for a shorter time in the closed arm of the elevated plus maze, and performed worse in the initial stage of the Morris water maze. To thermal stimuli, the ABCA1 and apoE KO mice showed hyper- and hypo-sensitivities, respectively. Only the response of the ABCA1 KO mice was significantly inhibited by pretreatment with indomethacin. A low concentration of the prostaglandin E metabolites was detected in the plasma of the ABCA1 KO mice. Thus, ABCA1 is thought to play a specific role in the neural function.

Synergistic interaction between B vitamins and statins to counter nociception in rats

Evidence suggests that the antinociceptive activity of various drugs can be increased when administered in combination with B vitamins (BVs). The aim of this study was to examine the potential interaction between statins and BVs to counter nociception, the latter measured by the formalin test. Rats were orally administered atorvastatin (1, 3, 10 and 30 mg/kg), pravastatin (1, 3, 10 and 30 mg/kg), rosuvastatin (1, 3, 10 and 30 mg/kg), BVs (31, 56, 100 and 180 mg/kg) or calculated combinations of BVs with each drug. The effective dose 30 (ED₃₀ ) was calculated for each statin and BVs and subjected to isobolographic analysis, thus finding the ED₃₀ of the combinations. The antinociceptive experimental ED₃₀ values for BVs administered with atorvastatin, pravastatin or rosuvastatin were 1.53 ± 0.38, 6.74 ± 0.04 and 4.26 ± 0.39, respectively, being lower (p < .05) than the corresponding theoretical ED₃₀ : 28.02 ± 2.20, 28.17 ± 2.20 and 29.86 ± 2.21. Since BVs likely boost the antinociceptive effect of statins, these combinations could possibly be advantageous in pain management.

Anti-inflammatory and anti-hypersensitive effects of the chalcone isocordoin and its semisynthetic derivatives in mice

Isocordoin (1), a chalcone isolated from different plants, has been found to present a range of interesting biological properties. This study aimed to evaluate the anti-hypersensitive and anti-inflammatory effects of isocordoin (1) and several natural and semisynthetic derivatives (2-10). Initial evaluation of (1), dihydroisocordoin (2) and six semisynthetic derivatives (3-8) in the inhibition of abdominal writhes induced by acetic acid model showed that only isocordoin dimethylether (5) caused more than 70% of inhibition. Further evaluation of 5 for its anti-oedematogenic activity and anti-hypersensitivity effect induced by carrageenan, lipopolysaccharide (LPS), bradykinin (BK), prostaglandin E2 (PGE2), and epinephrine showed that isocordoin dimethylether (5) presented a discrete inhibition of carrageenan- and LPS-induced hypersensitivity, and of carrageenan-induced paw oedema, and that it was able to significantly reduce both the oedema and hypersensitivity induced by BK. Furthermore, when tested in the PGE2 model, 5 interfered only with the paw-oedema, without showing any effect against the paw-hypersensitivity. Evaluation of the natural isocordoin (1), together with the semisynthetic derivatives isocordoin dimethylether (5), isocordoin methylether (9), and dihydroisocordoin methylether (10) in the BK-induced oedema and hypersensitivity showed that the monoalkylated derivatives 10 and 9 had the strongest antinociceptive activity. The results of this investigation indicate that both monoalkylation of the C-4' phenolic hydroxyl group and reduction of the double bond in the α,β-unsaturated system of the chalcone skeleton favor activity.

Prior statin therapy and mortality among critically ill patients: a systemic review and meta-analysis of cohort studies

The effect of prior statin exposure in critically ill patients remains controversial and has not been established in previous cohort studies. We performed a systematic review of previous cohort studies to evaluate the association of prior statin therapy with mortality in critically ill patients and conducted a meta-analysis. The MEDLINE, EMBASE, and Cochrane CENTRAL databases, from their inception to January 7, 2020, were used for this study. Statin users were defined as patients prescribed statin regularly before intensive care unit admission or diagnosis of a specific disease, such as sepsis. The Cochran chi-square test and I statistics were used to determine heterogeneity between studies. In total, 199,985 critically ill patients from nine studies (44,582 statin users and 155,403 non-statin users) were included in the meta-analysis. According to the random effect model, the 30-day mortality of statin users was 31% lower than that of non-statin users (hazard ratio: 0.69, 95% confidence interval: 0.56 to 0.85). This association was similar in atorvastatin users and simvastatin users. However, hospital mortality in statin users was not significantly associated with that in non-statin users [odds ratios (ORs): 0.71, 95% CI: 0.42 to 1.21]. This study showed that there was a beneficial association of prior statin therapy with 30-day mortality in critically ill patients. However, there was no significant association with hospital mortality. Additional prospective cohort studies with a large sample size should be performed to confirm these findings.

Peripheral nitric oxide signaling directly blocks inflammatory pain

Pain is a classical sign of inflammation, and sensitization of primary sensory neurons (PSN) is the most important mediating mechanism. This mechanism involves direct action of inflammatory mediators such as prostaglandins and sympathetic amines. Pharmacologic control of inflammatory pain is based on two principal strategies: (i) non-steroidal anti-inflammatory drugs targeting inhibition of prostaglandin production by cyclooxygenases and preventing nociceptor sensitization in humans and animals; (ii) opioids and dipyrone that directly block nociceptor sensitization via activation of the NO signaling pathway. This review summarizes basic concepts of inflammatory pain that are necessary to understand the mechanisms of peripheral NO signaling that promote peripheral analgesia; we also discuss therapeutic perspectives based on the modulation of the NO pathway.

Preoperative Statin Use and 90-Day Mortality after Noncardiac Surgery: A Hospital Registry Study

OBJECTIVE

The aim of this study was to investigate the association between preadmission statin use and 90-day mortality after planned elective noncardiac surgery in adult patients.

SUMMARY BACKGROUND DATA

Statin therapy is known to have pleiotropic effects, which improve the outcomes of various diseases. However, the effect of perioperative statin therapy on postoperative mortality remains controversial.

METHODS

This retrospective cohort study analyzed the medical records of adult patients who were admitted to a single tertiary academic hospital for elective noncardiac surgery between January 2012 and December 2018. The primary endpoint was 90-day mortality, which was defined as any mortality within 90 days after surgery. The secondary endpoint was overall survival.

RESULTS

After propensity score matching, a total of 33,514 patients (16,757 patients in each group) were included in the analysis. The logistic regression analysis of the propensity score-matched cohort indicated that the odds ratio (OR) of 90-day mortality in the statin group was 26% lower than that of the nonstatin group [OR: 0.74; 95% confidence interval (CI): 0.59 to 0.92; P = 0.009]. The sensitivity analysis indicated that the high-dose intensity statin group had a 61% lower 90-day mortality rate than the nonstatin group (OR: 0.39; 95% CI: 0.18-0.84; P = 0.016). The overall survival time was significantly longer in the statin group than in the nonstatin group after propensity score matching (P < 0.001 by log-rank test).

CONCLUSIONS

Preoperative statin use was associated with lower 90-day mortality and longer overall survival for adult patients who underwent elective noncardiac surgery. This association was more evident for high-intensity statin users.

Preadmission Statin Use and 90-day Mortality in the Critically Ill

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Background

This study aimed to examine the association between preadmission statin use and 90-day mortality in critically ill patients and to investigate whether this association differed according to statin type and dose. We hypothesized that preadmission statin use was associated with lower 90-day mortality.

Methods

This retrospective cohort study analyzed the medical records of all adult patients admitted to the intensive care unit in a single tertiary academic hospital between January 2012 and December 2017. Data including preadmission statin use, statin subtype, and daily dosage were collected, and the associations between these variables and 90-day mortality after intensive care unit admission were examined. The primary endpoint was 90-day mortality.

Results

A total of 24,928 patients (7,396 statin users and 17,532 non–statin users) were included. After propensity score matching, 5,354 statin users and 7,758 non–statin users were finally included. The 90-day mortality rate was significantly higher in non–statin users (918 of 7,758; 11.8%) than in statin users (455 of 5,354; 8.5%; P &lt; 0.001). In Cox regression analysis, the 90-day mortality rate was lower among statin users than among non–statin users (hazard ratio: 0.70, 95% CI: 0.63 to 0.79; P &lt; 0.001). Rosuvastatin use was associated with 42% lower 90-day mortality (hazard ratio: 0.58, 95% CI: 0.47 to 0.72; P &lt; 0.001). There were no specific significant differences in the association between daily statin dose and 90-day mortality. In competing risk analysis, the risk of noncardiovascular 90-day mortality in statin users was 32% lower than that in non–statin users (hazard ratio: 0.68, 95% CI: 0.60 to 0.78; P &lt; 0.001). Meanwhile, cardiovascular 90-day mortality was not significantly associated with statin use.

Conclusions

Preadmission statin use was associated with a lower 90-day mortality. This association was more evident in the rosuvastatin group and with noncardiovascular 90-day mortality; no differences were seen according to daily dosage intensity.

Are perioperative therapeutic doses of statins associated with postoperative pain and opioid consumption after hip surgery under spinal anaesthesia?

Background

The anti-inflammatory effects of statins have been suggested to relieve postoperative pain. This retrospective study tested the association between the perioperative routine use of statins in therapeutic doses, and opioid requirements and pain scores, after hip replacement surgery.

Methods

With IRB approval, data was obtained for adult patients who had elective hip replacement surgery under spinal anaesthesia at Cleveland Clinic between 2005 and 2015. Patients were compared using a joint hypothesis framework. We used the inverse probability of treatment weighting method to control for observed confounding factors (a total of 26).

Results

We included 611 statin users and 780 non-statin users. Pain score during the initial 72 h after surgery was 0.07 higher (95% CI: -0.02, 0.17) in statin users (noninferiority test in both directions P<0.001). The estimated ratio of geometric means in the cumulative i.v. morphine equivalent opioid consumption was 1.01 (95% CI: 0.93, 1.10) for statin vs non-statin users (noninferiority test P=0.001 in the hypothesized direction and<0.001 in the other direction) during the initial 72 h after surgery. The statin and non-statin patients were deemed equivalent on postoperative opioid consumption and pain score.

Conclusions

This is the first large retrospective clinical study that investigates the effects of statin use on postoperative pain and opioid consumption. We observed no difference between statin users and non-users during the initial 72 h after hip surgery. Our findings do not support the routine use of statins as part of an analgesic regimen.

Preadmission Statin Therapy Is Associated with a Lower Incidence of Acute Kidney Injury in Critically Ill Patients: A Retrospective Observational Study

This study aimed to investigate the association between preadmission statin use and acute kidney injury (AKI) incidence among critically ill patients who needed admission to the intensive care unit (ICU) for medical care. Medical records of patients admitted to the ICU were reviewed. Patients who continuously took statin for >1 month prior to ICU admission were defined as statin users. We investigated whether preadmission statin use was associated with AKI incidence within 72 h after ICU admission and whether the association differs according to preadmission estimated glomerular filtration rate (eGFR; in mL min⁻¹ 1.73 m⁻²). Among 21,236 patients examined, 5756 (27.1%) were preadmission statin users and 15,480 (72.9%) were non-statin users. Total AKI incidence within 72 h after ICU admission was 31% lower in preadmission statin users than in non-statin users [odds ratio (OR), 0.69; 95% confidence interval (CI), 0.61–0.79; p < 0.001]. This association was insignificant among individuals with eGFR <30 mL min⁻¹ 1.73 m⁻² (p > 0.05). Our results suggested that preadmission statin therapy is associated with a lower incidence of AKI among critically ill patients; however, this effect might not be applicable for patients with eGFR <30 mL min⁻¹ 1.73 m⁻².

Anti-hyperalgesic effects of two sphingosine derivatives in different acute and chronic models of hyperalgesia in mice

BACKGROUND

The study evaluated the effects of two sphingosine derivatives N-(2-tert-butoxycarbamylhexadecyl)glutaramide (AA) and N-(1-benzyloxyhexadec-2-yl)glutaramide (OA) in different models of hypersensitivity in mice.

METHODS

Male Swiss mice were orally pre-treated with AA or OA (0.3-3mg/kg). After 1h, they received λ-carrageenan (300μg/paw), lipopolysaccharide (LPS; 100ng/paw), bradykinin (BK; 500ng/paw) or prostaglandin E₂ (PGE₂; 0.1nmol/paw) or epinephrine (100ng/paw), and the mechanical withdrawal thresholds were evaluated using von Frey filament (0.6g) at different time points. The effect of the compounds against inflammatory and neuropathic pain was also evaluated using complete Freund's adjuvant (CFA), or by performing partial sciatic nerve ligation (PSNL).

RESULTS

Animals pre-treated with AA and OA reduced hypersensitivity induced by carrageenan, LPS and BK, and modest inhibition of PGE₂-induced hypersensitivity and carrageenan-induced paw oedema were observed in mice treated with OA. Though the partial effect presented by AA and OA, when dosed once a day, both compounds were able to significantly reduce the persistent inflammatory and neuropathic pain induced by CFA and PSNL, respectively.

CONCLUSION

These results demonstrate that the sphingosine derivatives AA and OA present important anti-hypersensitive effects, suggesting a possible interaction with the kinin signalling pathway. This may represent an interesting tool for the management of acute and chronic pain, with good bioavailability and safety.

Aspirin alone and combined with a statin suppresses eicosanoid formation in human colon tissue

Eicosanoids, including prostaglandins (PGs) and thromboxanes, are broadly bioactive lipid mediators and increase colon tumorigenesis possibly through chronic inflammatory mechanisms. Epidemiological and experimental data suggest that acetylsalicylic acid (ASA) helps prevent colorectal cancer (CRC), possibly through cyclooxygenase (COX)-mediated suppression of eicosanoid, particularly PGE2, formation. Recent studies suggest that statins prevent CRC and improve survival after diagnosis. We identified patients on ASA and/or statin treatment undergoing routine colonoscopy and measured eicosanoid levels in colonic mucosa with targeted metabolomics technology (LC-MS/MS). ASA-treated individuals (n = 27) had significantly lower tissue eicosanoid levels of most COX-derived metabolites than untreated individuals (n = 31). In contrast, COX-derived lipid metabolites tended to be higher in patients with statin treatment (n = 7) as compared with those not receiving statins (n = 24). This effect was not discernible in subjects treated with ASA and statins (n = 11): Individuals treated with both drugs showed a pronounced suppression of COX-derived eicosanoids in colon tissue, even compared with subjects treated with ASA alone. Our data from a routine clinical setting support the hypothesis that ASA and statins could inhibit CRC development via lipid mediator modification. Further studies should directly investigate the effect of dual ASA and statin treatment on colon tumorigenesis in humans.

Anti-hypersensitivity effects of the phthalimide derivative N-(4methyl-phenyl)-4-methylphthalimide in different pain models in mice

The treatment of chronic pain remains a challenge for clinicians worldwide, independent of its pathogenesis. It motivates several studies attempting to discover strategies to treat the disease. The in silico analysis using molecular docking approach demonstrated that the phthalimide N-(4methyl-phenyl)-4-methylphthalimide (MPMPH-1) presented high affinity to adenylyl-cyclase enzyme (AC). It also prominently reduced the mechanical hypersensitivity of mice challenged by Forskolin, an AC activator. This effect lasted for up to 48h after Forskolin injection, presenting activity longer than MDL-12330A (AC inhibitor). MPMPH-1 was also effective in reducing the hypersensitivity induced by IL-1β, bradykinin, prostaglandin E₂ or epinephrine, chemical mediators that have, among others, AC as pivotal protein in their signalling cascade to induce mechanical-pain behaviour. The compound presented marked inhibition in inflammatory-pain models induced by carrageenan, lipopolysaccharide or complete Freund's adjuvant, including neutrophil migration inhibition. Furthermore, it also seems to act in both peripheral and pain central-control pathways, being also effective in reducing the persistent cancer-pain behaviour induced by melanoma cells in mice. MPMPH-1 could represent a promising pharmacological tool to treat acute and chronic painful diseases, with good bioavailability, local activity, and lack of locomotor-activity interference. Further studies are necessary to determine the exact mechanism of action but it seems to involve AC enzyme as possible target.

Photobiomodulation therapy in the modulation of inflammatory mediators and bradykinin receptors in an experimental model of acute osteoarthritis

The objective of this study was to evaluate the effects of photobiomodulation therapy (PBMT) on inflammatory indicators, i.e., inflammatory mediators (TNF-α and CINC-1), and pain characterized by hyperalgesia and B1 and B2 receptor activation at 6, 24, and 48 h after papain-induced osteoarthritis (OA) in rats. Fifty-four rats were subjected to hyperalgesia evaluations and then divided randomly into three groups-a control group and two groups OA and OA PBMT group by using laser parameters at wavelength (808 nm), output power (50 mW), energy per point (4 Joules), power density (1.78 W/cm²), laser beam (0.028 cm²), and energy density (144 J/cm²)-the induction of osteoarthritis was then performed with 20-μl injections of a 4 % papain solution dissolved in 10 μl of saline solution, to which 10 μl of cysteine solution (0.03 M). The statistical analysis was performed using two-way ANOVA with Bonferroni's post hoc test for comparisons between the 6, 24, and 48 h and team points within each group, and between the control, injury, and PBMT groups, and p < 0.05 was considered to indicate a significant difference. The hyperalgesia was evaluated at 6, 24, and 48 h after the injury. PBMT at a wavelength of 808 nm and doses of 4 J, administered afterward, promotes increase at the threshold of pressure stimulus at 6, 24, and 48 h after application and promote cytokine attenuation levels (TNF and CINC-1) and bradykinin receptor (B1 and B2) along the experimental period. We conclude that photobiomodulation therapy was able to promote the reduction of proinflammatory cytokines such as TNF-α and CINC-1, to reduce the gene and protein expression of the bradykinin receptor (B1 and B2), as well as increasing the stimulus response threshold of pressure in an experimental model of acute osteoarthritis.

Involvement of inhibition of RhoA/Rho kinase signaling in simvastatin-induced amelioration of neuropathic pain

Small molecular G-protein plays a key role in several diseases. This study was designed to reveal the role of RhoA signaling in the pathophysiology of neuropathic pain in mice. Partial sciatic nerve injury caused thermal hyperalgesia, mechanical allodynia, and increased plasma membrane translocation of RhoA in the lumber spinal cord. GFAP-immunoreactivity (ir), Iba-1-ir, and Rho kinase 2 (ROCK2-ir) was also increased in the ipsilateral spinal dorsal horn of nerve-ligated mice. Moreover, partial nerve ligation increased the expression of phosphorylated myristoylated alanine-rich protein kinase C substrate (MARCKS)-ir in the ipsilateral spinal dorsal horn. Daily intrathecal administration of simvastatin, beginning 3days before nerve injury, completely blocked all these changes in nerve-ligated mice. Pharmacological inhibition of ROCK also attenuated the increased expression of GFAP-ir and phosphorylated MARCKS-ir. Together, it is suggested that astrogliosis initiated by the activation of RhoA/ROCK signaling results in MARCKS phosphorylation in nerve terminals, which leads to hyperalgesia in neuropathic pain. Furthermore, simvastatin exerts antihyperalgesic and antiallodynic effects through the inhibition of spinal RhoA activation.

Atorvastatin attenuates the antinociceptive tolerance of morphine via nitric oxide dependent pathway in male mice

The development of morphine-induced antinociceptive tolerance limits its therapeutic efficacy in pain management. Atorvastatin, or competitive inhibitor of 3-hydroxy-methyl-glutaryl coenzyme A (HMG-CoA) reductase, is mainstay agent in hypercholesterolemia treatment. Beyond the cholesterol-lowering activity, exploration of neuroprotective properties of this statin indicates its potential benefit in central nervous disorders. The aim of the present study was to assess the effects of atorvastatin in development and expression of morphine-induced analgesic tolerance in male mice and probable involvement of nitric oxide. Chronic and acute treatment with atorvastatin 10 and 20mg/kg, respectively, could alleviate morphine tolerance in development and expression phases. Chronic co-administration of nitric oxide synthase (NOS) inhibitors including L-NAME (non selective NOS inhibitor; 2mg/kg), aminoguanidine (selective inducible NOS inhibitor; 50mg/kg) and 7-NI (selective neuronal NOS inhibitor; 15mg/kg) with atorvastatin blocked the protective effect of atorvastatin in tolerance reversal. Moreover, reversing the atorvastatin effect was also observed in acute simultaneous treatment of L-NAME (5mg/kg) and aminoguanidine (100mg/kg) with atorvastatin. Co-treatment of guanylyl cyclase inhibitor, ODQ (chronic dose: 10mg/kg and acute dose: 20mg/kg) was associated with prevention of atorvastatin anti-tolerance properties. Our results revealed that the atorvastatin modulating role in morphine antinociceptive tolerance is mediated at least in part via nitric oxide in animal pain models of hot plate and tail flick.

Chrysophyllum cainito leaves are effective against pre-clinical chronic pain models: Analysis of crude extract, fraction and isolated compounds in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Chrysophyllum cainito L. (Sapotaceae), commonly known as caimito or star apple, is a neotropical tree valued for its ornamental quality and edible fruits. Besides its culinary use, the leaves are also popularly used to treat diabetes mellitus and several inflammatory diseases.

AIM OF THIS STUDY

This study aimed to complement previous data obtained about the anti-hypersensitivity effects of the crude methanol extract (CME), CHCl3 fraction and isolated compounds obtained from C. cainito.

MATERIALS AND METHODS

The CME, CHCl3 fraction and two isolated triterpenes identified as 3β-Lup-20(29)-en-3-yl acetate (1) and Lup-20(29)-en-3β-O-hexanoate (2) were evaluated regarding their effects using clinical pain models, such as post-operative, inflammatory and neuropathic pain. Acute inflammatory pain models induced by PGE2, epinephrine, LPS and CFA were also used to improve the knowledge about the mechanism of action.

RESULTS

The animals treated with the CME and submitted to PGE2, epinephrine, LPS or CFA had the mechanical hypersensitivity significantly reduced. When repeatedly administered, the CME enhanced the mechanical withdrawal threshold of mice submitted to post-operative pain model, CFA-induced chronic inflammatory pain and two different models of neuropathic pain. In turn, the CHCl3 fraction presented anti-hypersensitivity effect against epinephrine- or LPS-induced hypersensitivity, with a more prominent activity in both the neuropathic pain models. The compound 1 seems to present the same profile of the CHCl3, whereas compound 2 exhibited activity similar to the CME.

CONCLUSIONS

This data suggests that the CME effect involves interference in the production, release or action of some chemical mediators, such as PGE2, sympathetic amines, cytokines, etc. Part of these effects was observed with the CHCl3 fraction, emphasizing the prominent inhibition of neuropathic pain. The results also demonstrated that part of the CME effects are due to the presence of the triterpenes 1 and 2, but it is important to mention that we cannot discard the effects of countless other compounds presented in the crude extract, acting in a synergic way.

Naringenin reduces inflammatory pain in mice

Naringenin is a flavonoid widely consumed by humans that present anti-inflammatory activity and low toxicity. Recently, the analgesic effect of naringenin has been demonstrated in neuropathic pain models. Herein, we tested the analgesic effects of naringenin in several models of inflammatory pain. Mice received treatment with naringenin (16.7-150 mg/kg, per oral), or with the controls anti-inflammatory drugs indomethacin (5 mg/kg, intraperitoneal) or dipyrone (80 mg/kg, intraperitoneal) prior the inflammatory stimuli injection. For acute pain, we used acetic acid- and PBQ-induced visceral pain (abdominal writhings), and formalin-, capsaicin-, and CFA-induced paw flinching and licking. By using an electronic version of von Frey filaments, we also investigated the effects of naringenin in pain intensity to a mechanical stimulus (mechanical hyperalgesia) after carrageenan, capsaicin, CFA, or PGE2 intraplantar injection. Naringenin (50 mg/kg) reduced acute pain behaviors induced by all tested stimuli, including both phases of formalin test, suggesting a direct nociceptor modulatory effect of this compound besides its anti-inflammatory activity. Accordingly, naringenin also inhibited the increased sensitivity to mechanical stimulus induced by carrageenan, capsaicin, and PGE2. Daily treatment with naringenin during 7 days also reduced CFA-induced mechanical hyperalgesia without gastric or hepatic toxicity. The mechanisms of naringenin involve the inhibition of carrageenan-induced oxidative stress, hyperalgesic cytokines (IL-33, TNF-α, and IL-1β) production and NF-κB activation in the paw skin. Naringenin also activated the analgesic NO-cyclic GMP-PKG-ATP sensitive K(+) channel signaling pathway to inhibit carrageenan-induced mechanical hyperalgesia and neutrophil recruitment. These results suggest that naringenin inhibits both inflammatory pain and neurogenic inflammation.

Atorvastatin induced hepatic oxidative stress and apoptotic damage via MAPKs, mitochondria, calpain and caspase12 dependent pathways

Atorvastatin (ATO), a 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor, is used widely for the treatment of hypercholesterolemia and hypertriglyceridemia. Application of this drug has now been made somehow limited because of ATO associated several acute and chronic side effects. The present study has been carried out to investigate the dose-dependent hepatic tissue toxicity in ATO induced oxidative impairment and cell death in mice. Administration of ATO enhanced ALT, ALP level, increased reactive oxygen species (ROS) production and altered the pro oxidant-antioxidant status of liver by reducing intracellular GSH level, anti-oxidant enzymes activities and increasing intracellular lipid peroxidation. Our experimental evidence suggests that ATO markedly decreased mitochondrial membrane potential, disturbed the Bcl-2 family protein balance, enhanced cytochrome c release in the cytosol, increased the levels of Apaf1, caspase-9, -3, cleaved PARP protein and ultimately led to apoptotic cell death. Besides, ATO distinctly increased the phosphorylation of p38, JNK, and ERK MAPKs, enhanced Caspase12 and calpain level. Histological studies also support the dose-dependent toxic effect of ATO in these organs pathophysiology. These results reveal that ATO induces hepatic tissue toxicity via MAPKs, mitochondria and ER dependent signaling pathway, in which calcium ions and ROS act as the pivotal mediators of the apoptotic signaling.

Cytokines, but not corticotropin-releasing factor and endothelin-1, participate centrally in the febrile response in zymosan-induced arthritis in rats

Recent literature has revealed that centrally generated prostaglandins participate in the febrile response in zymosan-induced arthritis in rats. However, it is not clear whether other centrally acting pyrogenic mediators such as cytokines, endothelins (ETs), and the corticotropin-releasing factor (CRF) contribute to the febrile response in this model. In the present study, rats were pretreated with intracerebroventricular (i.c.v.) injections of soluble TNF receptor I (sTNFRI), recombinant IL-1 receptor antagonist (IL-1ra), anti-rat IL-6 monoclonal antibody (AbIL-6), α-helical CRF9-41 (a nonselective CRF1/CRF2 receptor antagonist), BQ-123 (an ETA receptor antagonist), BQ-788 (an ETB receptor antagonist), and artificial cerebrospinal fluid (aCSF, control) prior to an intra-articular zymosan (4 mg) injection. Rectal temperatures were measured with a telethermometer. The administration of IL-1ra (200 µg), sTNFRI (500 ng), and AbIL-6 (5 µg) attenuated body temperature elevations after a zymosan injection. The administration of BQ-788 (3 pmol), BQ-123 (3 pmol), and α-helical CRF9-41 (25 µg) did not affect the zymosan-induced febrile response. All the compounds used to pretreat the animals did not significantly alter their basal body temperatures. Together, the results here demonstrate that the febrile response in zymosan-induced arthritis in rats depends on the centrally acting pyrogenic cytokines TNF-α, IL-1β, and IL-6, but does not depend on either CRF or ET-1.

Protective effect of arjunolic acid against atorvastatin induced hepatic and renal pathophysiology via MAPK, mitochondria and ER dependent pathways

3-Hydroxy-3-methylglutaryl-CoA reductase inhibitor, atorvastatin (ATO), is a highly effective drug used for the treatment of hypercholesterolemia and hypertriglyceridemia. Its application is restricted now-a-days due to several acute and chronic side effects. ATO induced anti hypercholesterolemia and hepatic tissue toxicity has been reported to follow different mechanisms. The present study has been carried out to investigate the protective role of arjunolic acid (AA) against ATO induced oxidative impairment and cell death in hepatic and renal tissue in mice. Administration of ATO (at a dose 30 mg/kg/day for 8 weeks) enhanced serum markers, increased reactive oxygen species (ROS) production and altered the pro oxidant-antioxidant status of liver and kidney tissues. Our experimental evidence suggests that ATO exposure induces apoptotic cell deathby the activation of caspase-3 and reciprocal regulation of Bcl-2/Bax with the concomitant reduction of mitochondrial membrane potential and increased level of cytosolic cytochrome c, Apaf1, caspase-9. Besides, ATO markedly increased the phosphorylation of MAPKs, enhanced caspase-12 and calpain level. Histological studies and DNA fragmentation analysis also support the toxic effect of ATO in these organs pathophysiology. Post treatment with AA (at a dose of 20 mg/kg body weight for 4 days), however, reduced ATO-induced oxidative stress and suppressed all these apoptotic events. Results suggest that AA could effectively and extensively counteract these adverse effects and might protect liver and kidney from ATO-induced severe tissue toxicity.

The antihypersensitive and antiinflammatory activities of a benzofuranone derivative in different experimental models in mice: the importance of the protein kinase C pathway

BACKGROUND

Benzofuranone (BF1) was synthesized and its effects evaluated on mechanical hypersensitivity and paw edema models induced by different agents and on neuropathic pain induced by partial ligation of the sciatic nerve. An attempt was also made to elucidate the mechanism of action.

METHODS

Swiss mice were used for the tests. Hypersensitivity was induced by intraplantar injection of carrageenan, bradykinin (BK), prostaglandin E2 (PGE2), epinephrine, lipopolysaccharide, or complete Freund adjuvant or by using a neuropathic pain model (evaluated with von Frey filament 0.6 g). The antiinflammatory effects were investigated in a paw edema model induced by carrageenan, PGE2, and BK (measured with a plethysmometer). The involvement of protein kinase C (PKC) was investigated through a nociception model induced by phorbol myristate acetate.

RESULTS

BF1 inhibited the hypersensitivity and paw edema induced by intraplantar injection of carrageenan, BK, and PGE2 (P < 0.001), and it was effective in reducing the hypersensitivity evoked by complete Freund adjuvant or epinephrine (P < 0.001) but not by lipopolysaccharide (P = 0.2570). BF1 inhibited the licking behavior induced by phorbol myristate acetate (P < 0.001), suggesting involvement of the PKC pathway. A reduction in hypersensitivity of mice submitted to partial ligation of the sciatic nerve (P < 0.001) was observed, with inhibition of neutrophil migration and interleukin-1β production into the spinal cord. BF1 treatment did not interfere with locomotor activity (P = 0.0783) and thermal withdrawal threshold (P = 0.5953), which are important adverse effects of other analgesics.

CONCLUSIONS

BF1 has dose-dependent antihypersensitive and antiinflammatory effects in both acute and chronic models of pain and inflammation, possibly mediated through interference with the PKC activation pathway. The easy and fast synthesis of this compound, low-cost, low-concentration-requirement, and once-daily-administration drug suggest it as a candidate for future clinical studies.

Antinociceptive and antidiarrheal effects of pioglitazone in a rat model of diarrhoea-predominant irritable bowel syndrome: role of nitric oxide

Irritable bowel syndrome (IBS) is a prevalent disease characterized by abdominal pain and abnormal bowel habits. Pioglitazone is a peroxisome proliferator-activated receptor (PPAR) γ agonist and, although it is mostly used as an antidiabetic agent, it has been reported to have analgesic effects. Nitric oxide (NO), a gaseous molecule that mediates many of the effects of pioglitazone, has been implicated in the pathophysiology of IBS. The aim of the present study was to investigate the effects of pioglitazone on symptoms in a rat model of diarrhoea-predominant IBS (D-IBS).and to determine the role of NO in these effects. Diarrhoea-predominant IBS was induced by intracolonic instillation of acetic acid. Pioglitazone (2 mg/kg, i.p.) was administered on Days 7, 9 and 11 after acetic acid instillation. To investigate the mechanism involved in pioglitazone action, rats were also administered either the PPARγ antagonist GW9662 (3 mg/kg, i.p.), the NO synthase (NOS) inhibitor N(G) -nitro-l-arginine methyl ester (l-NAME; 10 mg/kg, i.p.) or the NO precursor l-arginine (250 mg/kg, i.p.) along with pioglitazone. Visceral hypersensitivity, nociceptive thresholds, defecation frequency, stool form, serum and colon NO production and inducible (i) NOS activity were assessed 1 h after the final injection of pioglitazone or dimethylsulphoxide (used as the vehicle). Pioglitazone reduced visceral hypersensitivity and defecation frequency, increased nociceptive thresholds, NO production and iNOS activity and shifted stool form towards hard stools in D-IBS rats. These effects of pioglitazone were significantly reversed by l-NAME, but not GW9662. l-Arginine augmented the effects of pioglitazone. In conclusion, pioglitazone alleviates symptoms in a rat model of D-IBS through an NO-dependent mechanism.

The ruthenium nitric oxide donor, [Ru(HEDTA)NO], inhibits acute nociception in mice by modulating oxidative stress, cytokine production and activating the cGMP/PKG/ATP-sensitive potassium channel signaling pathway

Nitric oxide plays an important role in various biological processes including antinociception. The control of its local concentration is crucial for obtaining the desired effect and can be achieved with exogenous nitric oxide-carriers such as ruthenium complexes. Therefore, we evaluated the analgesic effect and mechanism of action of the ruthenium nitric oxide donor [Ru(HEDTA)NO] focusing on the role of cytokines, oxidative stress and activation of the cyclic guanosine monophosphate/protein kinase G/ATP-sensitive potassium channel signaling pathway. It was observed that [Ru(HEDTA)NO] inhibited in a dose-dependent (1-10 mg/kg) manner the acetic acid-induced writhing response. At the dose of 1 mg/kg, [Ru(HEDTA)NO] inhibited the phenyl-p-benzoquinone-induced writhing response, and formalin- and complete Freund's adjuvant-induced licking and flinching responses. Systemic and local treatments with [Ru(HEDTA)NO] also inhibited the carrageenin-induced mechanical hyperalgesia and increase of myeloperoxidase activity in paw skin samples. Mechanistically, [Ru(HEDTA)NO] inhibited carrageenin-induced production of the hyperalgesic cytokines tumor necrosis factor-α and interleukin-1β, and decrease of reduced glutathione levels. Furthermore, the inhibitory effect of [Ru(HEDTA)NO] in the carrageenin-induced hyperalgesia and myeloperoxidase activity was prevented by the treatment with ODQ (soluble guanylyl cyclase inhibitor), KT5823 (protein kinase G inhibitor) and glybenclamide (ATP-sensitive potassium channel inhibitor), indicating that [Ru(HEDTA)NO] inhibits inflammatory hyperalgesia by activating the cyclic guanosine monophosphate/protein kinase G/ATP-sensitive potassium channel signaling pathway, respectively. These results demonstrate that [Ru(HEDTA)NO] exerts its analgesic effect in inflammation by inhibiting pro-nociceptive cytokine production, oxidative imbalance and activation of the nitric oxide/cyclic guanosine monophosphate/protein kinase G/ATP-sensitive potassium channel signaling pathway in mice.

Antihyperalgesic and anti-inflammatory effects of atorvastatin in chronic constriction injury-induced neuropathic pain in rats

Atorvastatin is a 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitor used in treatment of hypercholesterolemia and prevention of coronary heart disease. The aim of this study is to investigate the antihyperalgesic and anti-inflammatory effects of atorvastatin (3, 10, and 30 mg/kg by oral gavages for 14 days) in chronic constriction injury (CCI) model of neuropathic pain in rats. CCI caused significant increase in tumor necrosis factor-α, interleukin 1 beta, prostaglandin E2, along with matrix metalloproteases (MMP-2) and nerve growth factor (NGF) levels in sciatic nerve and spinal cord concomitant with mechanical and thermal hyperalgesia, which were significantly reduced by oral administration of atorvastatin for 14 days as compared to CCI rats. Our study demonstrated that atorvastatin attenuates neuropathic pain through inhibition of cytokines, MMP-2, and NGF in sciatic nerve and spinal cord suggesting that atorvastatin could be an additional therapeutic strategy in management of neuropathic pain.

Gabapentin prevents oxaliplatin-induced mechanical hyperalgesia in mice

Oxaliplatin, a platinum-based chemotherapy drug, frequently causes acute and chronic peripheral neuropathies including mechanical hyperalgesia. These adverse effects hinder anticancer therapy with the drug. In this study, we examined several drugs that might prevent oxaliplatin-induced peripheral neuropathy. Single intraperitoneal (i.p.) injection of oxaliplatin (10 mg/kg) induced cold allodynia (acetone test) and mechanical hyperalgesia (von Frey test). Gabapentin, but not simvastatin and atorvastatin, prevented oxaliplatin-induced mechanical hyperalgesia without affecting cold allodynia. Moreover, oxaliplatin caused phosphorylation of cofilin protein in the spinal cord, which has been shown to be involved in the neuropathic hyperalgesia. This increased phosphorylation of cofilin was also attenuated by gabapentin treatment. These results suggest that gabapentin is useful for relieving oxaliplatin-induced mechanical hyperalgesia and that the pathogenic mechanisms of cold allodynia and mechanical hyperalgesia differ.

Atorvastatin exerts anti-nociceptive activity and decreases serum levels of high-sensitivity C-reactive protein and tumor necrosis factor-α in a rat endometriosis model

PURPOSE

The purpose of this study was to examine the effects of atorvastatin in the treatment of experimental endometriosis.

METHODS

Endometriosis was induced in 24 female rats. 4 weeks after the procedure dimensions of the foci were recorded. Rats were divided into three groups: in Group 1 (n = 8), a daily dose of 10 mg/kg atorvastatin was given for 14 days. In the second group (n = 8), a single dose of 1 mg/kg leuprolide acetate was injected intraperitoneally. The rats in Group 3 (n = 8) were received 1 mg/kg i.p. 0.9 % NaCl. At the end of the treatment, laparotomy was performed, and the dimensions of the endometriotic foci were recorded. Biochemical, histopathological and immunohistochemical studies were performed and nociception was compared in groups.

RESULTS

Atorvastatin treatment exhibited significant analgesic activity in hot plate model (P = 0.022). The serum hs-CRP and tumor necrosis TNF-α levels were similar between the Group 2 and Group 3 (P > 0.05); however atorvastatin caused significant decrease in both serum markers. The histological and immunohistochemical scores were also found to be markedly lower in Group 1 and Group 2 (P < 0.05).

CONCLUSION

Atorvastatin treatment may have a therapeutic potential in the treatment of endometriosis through its anti-inflammatory and anti-nociceptive properties.

Nitroxyl inhibits overt pain-like behavior in mice: role of cGMP/PKG/ATP-sensitive potassium channel signaling pathway

BACKGROUND

Several lines of evidence have indicated that nitric oxide (NO) plays complex and diverse roles in modulation of pain/analgesia. However, the roles of charged and uncharged congeners of NO are less well understood. In the present study, the antinociceptive effect of the nitroxyl (HNO) donor, Angeli's salt (Na2N2O3; AS) was investigated in models of overt pain-like behavior. Moreover, whether the antinociceptive effect of nitroxyl was dependent on the activation of cGMP (cyclic guanosine monophosphate)/PKG (protein kinase G)/ATP-sensitive potassium channels was addressed.

METHODS

The antinociceptive effect of AS was evaluated on phenyl-p-benzoquinone (PBQ)- and acetic acid-induced writhings and via the formalin test. In addition, pharmacological treatments targeting guanylate cyclase (ODQ), PKG (KT5923) and ATP-sensitive potassium channel (glybenclamide) were used.

RESULTS

PBQ and acetic acid induced significant writhing responses over 20min. The nociceptive response in these models were significantly reduced in a dose-dependent manner by subcutaneous pre-treatment with AS. Furthermore, AS also inhibited both phases of the formalin test. Subsequently, the inhibitory effect of AS in writhing and flinching responses were prevented by ODQ, KT5823 and glybenclamide, although these inhibitors alone did not alter the writhing score. Furthermore, pretreatment with L-cysteine, an HNO scavenger, confirmed that the antinociceptive effect of AS depends on HNO.

CONCLUSION

The present study demonstrates the efficacy of a nitroxyl donor and its analgesic mechanisms in overt pain-like behavior by activating the cGMP/PKG/ATP-sensitive potassium channel (K(+)) signaling pathway.

Neuro, cardio, and reno protective activities of rosuvastatin in streptozotocin-induced type 2 diabetic rats undergoing treatment with metformin and glimepiride

Diabetes is associated with complications like neuropathy, nephropathy, cardiomyopathy, and retinopathy due to increased oxidative stress and serum lipids. In the present study, rosuvastatin, a HMG-CoA inhibitor, was investigated for its protective effect in neuropathy, nephropathy, and cardiomyopathy based on the lipid-lowering property along with its pleiotropic effects such as improved blood flow to the organ and antioxidant defense. Type 2 diabetes was induced in Wistar rats by single i.p. administration of streptozotocin (50 mg/kg). These diabetic rats were treated with daily doses of rosuvastatin (10 mg/kg) alone, metformin (120 mg/kg) and glimepiride (1 mg/kg) and rosuvastatin in combination with metformin (120 mg/kg) and glimepiride (1 mg/kg) for a period of 6 weeks. The biochemical parameters involved in neuropathy, renopathy, and cardiopathy were estimated. Treatment resulted in significant (P < 0.05) decrease in thiobarbituric acid reactive substances (TBARS) and increase in levels of glutathione peroxidise and catalase in brain and kidney homogenates. Significant (P < 0.05) increase in high-density lipoproteins and decrease in creatinine kinase, triglycerides, total serum cholesterol represents the cardioprotective action, whereas significant (P < 0.05) increase in the latency in the hotplate model shows the neuroprotective activity, and significant (P < 0.05) decrease in blood urea nitrogen, creatinine levels and increase in serum total protein levels suggested the renoprotective actions. The unique properties of rosuvastatin such as antioxidant defense and lipid-lowering nature might have resulted in cardio, neuro, and renoprotective activity in type 2 diabetic rats treated with metformin and glimepiride.

Experimental evaluation of analgesic and anti-inflammatory activity of simvastatin and atorvastatin

Aim:

The aim of this study is to evaluate the analgesic and anti-inflammatory activities of atorvastatin and simvastatin in different experimental models in mice and rats.

Materials and Methods:

Analgesic activity of simvastatin and atorvastatin was assessed in tail flick model in rats (n = 6), where it was compared with aspirin and tramadol and in acetic acid induced writhing in mice (n = 6), where it was compared with aspirin. Anti-inflammatory activity of statins was evaluated using carrageenin induced paw edema and formalin induced arthritis in rats.

Results:

In the tail flick method, analgesic effect of tramadol was significantly more than the other drugs except at two observation times, when it was comparable to simvastatin and atorvastatin. Effect of simvastatin was found to be comparable to aspirin. In acetic acid induced writhing method, analgesic activity of simvastatin was comparable to that of aspirin while that of atorvastatin was significantly less. In carrageenin induced paw edema in rats, both simvastatin and atorvastatin showed anti-inflammatory activity which was comparable to aspirin. Both the statins exhibited significant anti-inflammatory activity (P < 0.01) in formalin induced arthritis model though less than aspirin (P < 0.05).

Conclusion:

The results of this study if substantiated by further experimental and clinical research suggest that simvastatin and atorvastatin may play an adjuvant role, which may be particularly beneficial in the treatment of inflammatory disorders, especially when there is coexisting dyslipidemia.

The nitroxyl donor, Angeli's salt, inhibits inflammatory hyperalgesia in rats

Nitric oxide modulates pain development. However, there is no evidence on the effect of nitroxyl (HNO/NO⁻) in nociception. Therefore, we addressed whether nitroxyl inhibits inflammatory hyperalgesia and its mechanism using the nitroxyl donor Angeli's salt (AS; Na₂N₂O₃). Mechanical hyperalgesia was evaluated using a modified Randall and Selitto method in rats, cytokine production by ELISA and nitroxyl was determined by confocal microscopy in DAF (a cell permeable reagent that is converted into a fluorescent molecule by nitrogen oxides)-treated dorsal root ganglia neurons in culture. Local pre-treatment with AS (17-450 μg/paw, 30 min) inhibited the carrageenin-induced mechanical hyperalgesia in a dose- and time-dependent manner with maximum inhibition of 97%. AS also inhibited carrageenin-induced cytokine production. AS inhibited the hyperalgesia induced by other inflammatory stimuli including lipopolysaccharide, tumor necrosis factor-α, interleukin-1β and prostaglandin E2. Furthermore, the analgesic effect of AS was prevented by treatment with ODQ (a soluble guanylate cyclase inhibitor), KT5823 (a protein kinase G [PKG] inhibitor) or glybenclamide (an ATP-sensitive K⁺ channel blocker), but not with naloxone (an opioid receptor antagonist). AS induced concentration-dependent increase in fluorescence intensity of DAF-treated neurons in a l-cysteine (nitroxyl scavenger) sensitive manner. l-cysteine did not affect the NO⁺ donor S-Nitroso-N-acetyl-DL- penicillamine (SNAP)-induced anti-hyperalgesia or fluorescence of DAF-treated neurons. This is the first study to demonstrate that nitroxyl inhibits inflammatory hyperalgesia by reducing cytokine production and activating the cGMP/PKG/ATP-sensitive K⁺ channel signaling pathway in vivo.

The ruthenium NO donor, [Ru(bpy)2(NO)SO3](PF6), inhibits inflammatory pain: involvement of TRPV1 and cGMP/PKG/ATP-sensitive potassium channel signaling pathway

The activation of nitric oxide (NO) production is an analgesic mechanism shared by drugs such as morphine and diclofenac. Therefore, the controlled release of low amounts of NO seems to be a promising analgesic approach. In the present study, the antinociceptive effect of the ruthenium NO donor [Ru(bpy)2(NO)SO3](PF6) (complex I) was investigated. It was observed that complex I inhibited in a dose (0.3-10mg/kg)-dependent manner the acetic acid-induced writhing response. At the dose of 1mg/kg, complex I inhibited the phenyl-p-benzoquinone-induced writhing response and formalin- and complete Freund's adjuvant-induced licking and flinch responses. Additionally, complex I also inhibited transient receptor potential cation channel subfamily V member 1 (TRPV1)-dependent overt pain-like behavior induced by capsaicin. Complex I also inhibited the carrageenin-induced mechanical hyperalgesia and increase of myeloperoxidase activity (MPO) in paw skin samples. The inhibitory effect of complex I in the carrageenin-induced hyperalgesia, MPO activity and formalin was prevented by the treatment with ODQ, KT5823 and glybenclamide, indicating that complex I inhibits inflammatory hyperalgesia by activating the cGMP/PKG/ATP-sensitive potassium channel signaling pathway. The present study demonstrates the efficacy of a novel ruthenium NO donor and its analgesic mechanisms.

Euphol, a tetracyclic triterpene produces antinociceptive effects in inflammatory and neuropathic pain: the involvement of cannabinoid system

Persistent pains associated with inflammatory and neuropathic states are prevalent and debilitating diseases, which still remain without a safe and adequate treatment. Euphol, an alcohol tetracyclic triterpene, has a wide range of pharmacological properties and is considered to have anti-inflammatory action. Here, we assessed the effects and the underlying mechanisms of action of euphol in preventing inflammatory and neuropathic pain. Oral treatment with euphol (30 and 100 mg/kg) reduced carrageenan-induced mechanical hyperalgesia. Likewise, euphol given through the spinal and intracerebroventricular routes prevented mechanical hyperalgesia induced by carrageenan. Euphol consistently blocked the mechanical hyperalgesia induced by complete Freund's adjuvant, keratinocyte-derived chemokine, interleukin-1β, interleukin-6 and tumor necrosis factor-alpha associated with the suppression of myeloperoxidase activity in the mouse paw. Oral treatment with euphol was also effective in preventing the mechanical nociceptive response induced by ligation of the sciatic nerve and also significantly reduced the levels and mRNA of cytokines/chemokines in both paw and spinal cord tissues following i.pl. injection of complete Freund's adjuvant. In addition, the pre-treatment with either CB₁R or CB₂R antagonists, as well as the knockdown gene of the CB₁R and CB₂R, significantly reversed the antinociceptive effect of euphol. Interestingly, even in higher doses, euphol did not cause any relevant action in the central nervous system. Considering that few drugs are currently available for the treatment of chronic pain states, the present results provided evidence that euphol constitutes a promising molecule for the management of inflammatory and neuropathic pain states.

Effect of spinally administered simvastatin on the formalin-induced nociceptive response in mice

Clinical and experimental observations indicated that 3-hydroxy-3-methylglutaryl CoA reductase inhibitor statins have pleiotropic effects. The present study determined the antinociceptive property of centrally administered simvastatin on the formalin-induced nociception in the mouse. Intrathecal administration of simvastatin at doses of 0.5 - 50 nmol dose-dependently attenuated the second, but not the first, phase of the formalin-induced nociception, which was partially reversed by mevalonate (5 µmol). Intracerebroventricular injection of simvastatin (50 nmol) did not affect the formalin-induced nociception. These results suggest that simvastatin-induced antinociception is mediated by attenuation of the sensitization of spinal nociceptive transmission.

Antinociceptive and anti-inflammatory effects of a lectin-like substance from Clitoria fairchildiana R. Howard seeds

Lectins are proteins that have the ability to bind specifically and reversibly to carbohydrates and glycoconjugates, without altering the structure of the glycosyl ligand. They are found in organisms such as viruses, plants and humans, and they have been shown to possess important biological activities. The objective of this study was to purify and characterize lectins in the seeds of Clitoria fairchildiana, as well as to verify their biological activities. The results indicated the presence of a lectin (CFAL) in the glutelin acid protein fraction, which agglutinated native rabbit erythrocytes. CFAL was purified by column chromatography ion-exchange, DEAE-Sephacel, which was obtained from a peak of protein retained in the matrix by applying 0.5 M NaCl using the step-wise method. Electrophoretic analysis of this lectin in SDS-PAGE indicated a two band pattern protein molecular mass of approximately 100 and 116 kDa. CFAL proved to be unspecific to all carbohydrates/glycoconjugates in common use for the sugar inhibition test. This lectin showed no significant cytotoxicity to human red blood cells. It was observed that CFAL has anti-inflammatory activity in the paw edema induced by carrageenan model, in which a 64% diminution in edema was observed. Antinociceptive effects were observed for CFAL in the abdominal writhing test (induced by acetic acid), in which increasing doses of the lectin caused reduction in the number of contortions by up to 72%. It was concluded that the purified and characterized lectin from the seeds of Clitoria fairchildiana has anti-inflammatory and antinociceptive activity, and is not cytotoxic to human erythrocytes.

Neuroprotective and Anti-Inflammatory Activities of Atorvastatin in a Rat Chronic Constriction Injury Model

Atorvastatin is an HMG-CoA reductase inhibitor used to treat hypercholesterolemic conditions associated with hypertension. This study aims to investigate the anti-inflammatory and neuroprotective effects of atorvastatin on peripheral neuropathic pain. Peripheral neuropathic pain was induced by chronic constriction injury (CCI) in Sprague-Dawley rats. Rats were divided into 3 groups including sham-operated, CCI, and atorvastatin-treated. Atorvastatin (10 mg/kg) or phosphate-buffered saline was orally administered for 2 weeks. All animals were assessed by neurobehavioral tests before surgery and at days 3, 7, 14 after surgery. Inflammatory and neuroprotective factors were evaluated by Western blot analysis. eNOS, COX2 and iNOS in the sciatic nerve were also studied using immunohistochemistry. Atorvastatin attenuated CCI-induced nociceptive sensitization and thermal hyperalgesia in a time-dependent manner. Atorvastatin improved CCI-induced neurobehavioral/inflammatory activity by inhibition of TGF-β, PIκB/IκB, NFκB, COX2, iNOS, EP1 and EP4 in the sciatic nerve. Atorvastatin was also found to increase neuroprotection factors pAkt/Akt, eNOS and VEGF. Taken together, these data indicate that atorvastatin could protect the sciatic nerve against CCI-induced neuroinflammation and nociception.

Plant derived alkaloid (-)-cassine induces anti-inflammatory and anti-hyperalgesics effects in both acute and chronic inflammatory and neuropathic pain models

Natural products have been revealed as relevant sources of therapeutic agents including those for the management of pain states. In this study, the anti-nociceptive and anti-inflammatory effects of (-)-cassine, isolated from Senna spectabilis were evaluated using pharmacological, behavioural and biochemical approaches. Oral treatment with (-)-cassine (3-30 mg/kg) reduced carrageenan-induced mechanical and thermal nociception associated with the suppression of myeloperoxidase activity in the mouse paw. Moreover, (-)-cassine (1-10 μg/site) prevented mechanical hyperalgesia induced by carrageenan when given through the intraplantar (i.pl.), spinal and intracerebroventricular routes. Additionally, oral treatment with (-)-cassine (3-60 mg/kg) prevented the mechanical hyperalgesia elicited by intraplantar injection of prostaglandin E(2), complete Freund's adjuvant, interleukin-1β, interleukin-6 and keratinocyte-derived chemokine. Furthermore, (-)-cassine inhibited the mechanical nociceptive response induced by ligation of the sciatic nerve and also significantly reduced the levels of cytokines/chemokines in paw tissue following i.pl. injection of carrageenan. In addition, the anti-nociceptive and anti-inflammatory actions of (-)-cassine were associated with its ability to interact with both TRPV1 and TRPA1 receptors and by inhibiting the upregulation of cyclooxigenase-2 as well as inhibiting the phosphorylation of MAPK/ERK and the transcription factor NF-κB. It is important to highlight that oral treatment with (-)-cassine did not produce any effects related to temperature, locomotor activity or catalepsy. Altogether, the present data demonstrate that (-)-cassine has systemic, spinal and supraspinal anti-nociceptive properties when assessed in inflammatory and neuropathic pain models. These effects are associated with its ability to block several signalling pathways associated with inflammatory and nociceptive responses. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

Antinociception and anti-inflammation induced by simvastatin in algesiometric assays in mice

Statins, belonging to a well-known drug class used for lowering cholesterol through competitive inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, also have other pleiotropic properties, such as anti-inflammatory action. The purpose of this study was to evaluate the antinociceptive and anti-inflammatory effects of simvastatin in five models of nociceptive behaviour. Oral gavage administration of simvastatin induced a dose-dependent inhibition of nociception for 1 day in the acetic acid writhing (ED(50) = 5.59 ± 0.07), tail-flick (ED(50) = 112.96 ± 8.00), hot-plate (ED(50) = 134.87 ± 2.20), formalin hind paw (ED(50) = 19.86 ± 1.12 in phase I and 23.30 ± 2.05 in phase II) and orofacial formalin (ED(50) = 5.54 ± 2.74 in phase I and 11.48 ± 1.88 in phase II) tests. However, after 3 days, the values were in the acetic acid writhing (ED(50) = 6.14 ± 0.51), tail-flick (ED(50) = 154 ± 8.88), hot-plate (ED(50) = 136.14 ± 2.94), formalin hind paw (ED(50) = 15.93 ± 0.42 in phase I and 17.10 ± 1.80 in phase II) and orofacial formalin (ED(50) = 6.79 ± 0.66 in phase I and 5.80 ± 1.49 in phase II) tests. This study demonstrated the antinociceptive and anti-inflammatory activities of simvastatin in five models of tonic or phasic pain. These actions seem to be related to the inhibition of cytokine and prostanoid release and stimulation of nitric oxide synthesis. A possible clinical role of simvastatin could be related to the potentially beneficial effects in the neuropathic pain, and by their pleiotropic properties, they could play a clinical role in anti-inflammatory disease.