Cyclosporin inhibits hyperalgesia and edema in arthritic rats: role of the central nervous system

Nanogels as Novel Nanocarrier Systems for Efficient Delivery of CNS Therapeutics

Nanogels have come out as a great potential drug delivery platform due to its prominently high colloidal stability, high drug loading, core-shell structure, good permeation property and can be responsive to environmental stimuli. Such nanoscopic drug carriers have more excellent abilities over conventional nanomaterials for permeating to brain parenchyma in vitro and in vivo. Nanogel-based system can be nanoengineered to bypass physiological barriers via non-invasive treatment, rendering it a most suitable platform for the management of neurological conditions such as neurodegenerative disorders, brain tumors, epilepsy and ischemic stroke, etc. Therapeutics of central nervous system (CNS) diseases have shown marked limited site-specific delivery of CNS by the poor access of various drugs into the brain, due to the presences of the blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier (BCSFB). Hence, the availability of therapeutics delivery strategies is considered as one of the most major challenges facing the treatment of CNS diseases. The primary objective of this review is to elaborate the newer advances of nanogel for CNS drugs delivery, discuss the early preclinical success in the field of nanogel technology and highlight different insights on its potential neurotoxicity.

Effects of dexamethasone and acetylsalicylic acid on inflammation caused by complete Freund’s adjuvant in the naked mole rat (Heterocephalus glaber)

The naked mole rat (NMR) is a fossorial rodent that has been observed to have a unique nociceptive system in comparison to others. In this study, we explored on characterization of chronic inflammation in the NMR using Complete Freund's adjuvant (CFA) and investigated the effects of dexamethasone and acetylsalicylic acid on the resulting inflammation. The NMRs were injected with 0.1 ml of CFA subcutaneously in the right hind paw, and an equivalent volume of normal saline was injected to the control group. Swelling of the injected right hind limb was observed within 24 h of injection, which involved the tibiotarsal joint, palmar surface and the digits of the injected paw. Swelling persisted for 6 weeks of experimentation and peaked between day 14 and 21. The resulting inflammation affected the mobility, stance and joint rigidity of CFA treated NMRs in comparison to the control group. Treatment of the chronic phase of the inflammation from the 11^th day with dexamethasone and acetylsalicylic acid showed no statistical significance in paw circumference compared to the control group, other than on a few, negligible occasions. The present data showed that CFA was able to induce chronic inflammation in the NMR, and the NMR could thus be established as a model for chronic inflammation. There is, however, need for more sensitive parameters to evaluate the effects of anti-inflammatory drugs.

Central Administration of Cyclosporine A Decreases Ethanol Drinking

Aims

Abstinence among alcohol dependent liver graft recipients is remarkably high. The routine use of anti-immune agents in these patients led to rodent studies showing that immunosuppressants acting through inhibition of calcineurin (CLN) are highly effective in decreasing alcohol consumption. It remained unclear, however, whether the decreased alcohol consumption in rodent models is mediated through peripheral suppression of immune response or centrally through direct inhibition of cyclophilin-CLN in the brain. We tested the hypothesis that direct brain inhibition of CLN with intracerebroventricular (ICV) injections of the immunosuppressant cyclosporine A (CsA) is sufficient to decrease ethanol consumption in a rodent model of binge-like drinking.

Methods

Male C57BL/6NHsd mice were put through a modified 'drinking in the dark' (DID) paradigm. Effects of both peripheral (IP) and central (ICV) injections of CsA on ethanol consumption were assessed.

Results

Here, as in earlier work, IP CsA administration significantly decreased alcohol consumption. Supporting our hypothesis, central administration of CsA was sufficient to decrease alcohol consumption in a dose-dependent manner. There was no significant effect of CsA on water or sucrose consumption.

Conclusions

These results clearly implicate a CLN-mediated mechanism in brain in the inhibitory effects of CsA on ethanol consumption and provide novel targets for investigation of treatment for Alcohol Use Disorders (AUD). These results also add to the growing body of literature implicating neuroimmune mechanisms in the etiology, pathophysiology and behaviors driving AUD.

Short Summary

The unusually high abstinence rate and routine use of immunosuppressants in AUD liver graft recipients led us to rodent studies showing that immunosuppressants acting through inhibition of calcineurin (CLN) are highly effective in decreasing drinking. Here we demonstrate that this effect is mediated by brain rather than peripheral immune mechanisms.

Calcineurin inhibitors improve memory loss and neuropathological changes in mouse model of dementia

AIM

The present study was designed to investigate the potential of Cyclosporine (CsA) and Tacrolimus, the inhibitors of calcineurin (CaN) in cognitive deficits of mice.

METHODS

Streptozotocin [STZ, 3mg/kg, injected intracerebroventricular (i.c.v.)] was used to induce memory deficits in NIH mice, while aged mice separately taken served as a natural model of dementia. Morris water maze (MWM) test was employed to evaluate learning and memory of the animals. A battery of biochemical and histopathological studies was also performed. Extent of oxidative stress was measured by estimating the levels of brain glutathione (GSH) and thiobarbituric acid reactive species (TBARS). Brain acetylcholinestrase (AChE) activity was estimated to assess cholinergic activity. The brain level of myeloperoxidase (MPO) was measured as a marker of inflammation.

RESULTS

STZ i.c.v. and aging results in marked decline in MWM performance of the animals, reflecting impairment of learning and memory. STZ i.c.v. treated mice and aged mice exhibited a marked accentuation of AChE activity, TBARS and MPO levels along with a fall in GSH level. Further the stained micrographs of STZ treated mice and aged mice indicate pathological changes, severe neutrophilic infiltration and amyloid deposition. Cyclosporine and Tacrolimus treatment significantly attenuated STZ induced and age related memory deficits, biochemical and histopathological alterations.

CONCLUSION

The findings demonstrate the potential of CaN inhibitors Cyclosporine and Tacrolimus in memory dysfunctions which may probably be attributed to anti-cholinesterase, anti-amyloid, anti-oxidative and anti-inflammatory effects. It is concluded that CaN can be explored as a potential therapeutic target in dementia.

Treatment with Selemax®, a selenium-enriched yeast, ameliorates experimental arthritis in rats and mice

Rheumatoid arthritis (RA) is a chronic inflammatory disease that mainly targets the synovial membrane, cartilage and bone. It affects 1 % of the population and is associated with significant morbidity and increased mortality. Se is an essential trace element with antioxidant properties and the ability to modulate the immune responses. Selemax® is an inactive yeast (Saccharomyces cerevisiae) enriched with organic Se. The aim of the present study was to investigate the effects of Selemax® administration in models of an antigen-induced arthritis (AIA) in C57BL/6 mice, and of an adjuvant-induced arthritis (AdIA) in Holtzman rats. As control, the animals were treated with the same inactivated yeast species that was not enriched for Se. In the AIA model, treatment with different doses of Selemax® (0·01, 0·1, 1 and 10 % added to food) significantly decreased the number of inflammatory cells recruited to the knee cavity, essentially by reducing the number of neutrophils. Levels of proinflammatory cytokines, including TNF-α, IL-1β and chemokine (C-X-C motif) ligand 1/keratinocyte chemoattractant (CXCL1/KC), were also reduced in the peri-articular tissue of mice treated with Selemax® at the tested dose (1 %). In the AdIA model in rats, Selemax® treatment decreased paw oedema and hypernociception. This reduction was associated with inhibition of the influx of proinflammatory cells. Therefore, treatment with Selemax® is associated with amelioration of several inflammatory and functional parameters in models of arthritis, suggesting that this Se-enriched yeast should be evaluated further in patients with RA.

Spinal mu-opioid receptor expression and hyperalgesia with dexamethasone in chronic adjuvant-induced arthritis in rats

1. It is known that inflammation influences peripheral and central mu-opioid receptor expression. Previous studies have indicated that glucocorticoids may influence the density of mu-opioid receptors. In the present study, we investigated the fluctuations of spinal mu-opioid receptor expression and hyperalgesia induced by complete Freund's adjuvant (CFA) under long-term administration of dexamethasone. 2. Adjuvant arthritis (AA) was induced by subcutaneous injection of CFA in the right hindpaw of male Wistar rats. Spinal mu-opioid receptor expression was detected by semiquantitative reverse transcription-polymerase chain reaction on Days 6 and 21 following AA induction. Dexamethasone (0.1 mg/kg) was administered intraperitoneally for 21 days. Variations in thermal hyperalgesia were checked by radiant heat on the same days as mu-opioid receptor expression was determined. 3. The results indicated a significant increase in spinal mu-opioid receptor expression on Days 6 and 21 after AA induction compared with the control group. Spinal mu-opioid receptor expression decreased significantly only on Day 21 in the AA + dexamethasone group compared with the AA alone group. Thermal hyperalgesia on Day 6 after AA induction showed a significant increase compared with the control group. Hyperalgesia decreased significantly on Day 21 after AA compared with Day 6. The AA + dexamethasone group showed a significant decrease in hyperalgesia on Day 6 compared with the AA group, but hyperalgesia increased significantly on Day 21 in the AA + dexamethasone group compared with the AA group. 4. The effects of long-term dexamethasone on both spinal mu-opioid receptor expression and hyperalgesia during persistent AA inflammation are time dependent. In addition, the effect of long-term dexamethasone administration on hyperalgesia during persistent arthritis inflammation needs to be investigated further.

Anti-inflammatory and analgesic effects of atorvastatin in a rat model of adjuvant-induced arthritis

Statins exert favorable effects on lipoprotein metabolism but may also possess anti-inflammatory effects. Here, we explored the effects of atorvastatin in a model of adjuvant-induced arthritis in rat. Oral treatment with atorvastatin (1-10 mg/kg) from days 10 to 15 after arthritis induction caused inhibition of the increase in paw volume. Maximal inhibition occurred at a dose of 10 mg/kg. At this dose, atorvastatin markedly ameliorated the histopathological findings of joints obtained from day 16 of arthritic animals. This was mirrored by an effective blockade of neutrophil influx, as assessed by the tissue myeloperoxidase levels. The concentrations of the cytokines interleukin-1beta, interleukin-6 and tumor necrosis factor-alpha and the chemokines CCL5 and CCL2 were significantly decreased in arthritic rats treated with atorvastatin. In contrast, the levels of interleukin-10 were enhanced by the drug treatment. The drug also prevented the hypernociception observed in the inflamed joints. These data clearly illustrate the therapeutic potential of a statin-sensitive pathway in inflammatory arthritis.

FK506 ameliorates spontaneous locomotor activity in collagen-induced arthritis: implication of distinct effect from suppression of inflammation

FK506 (tacrolimus), an immunosuppressive drug, improves quality of life (QOL) for patients with rheumatoid arthritis (RA). However, the mechanism of FK506 behind the improvement in QOL is still uncharacterized. To explain the improvement of QOL by FK506, we investigated the effect of FK506 on spontaneous locomotor activity in rats with collagen-induced arthritis (CIA). CIA was induced in 7- to 8-week-old female Lewis rats by immunization with bovine type II collagen. After initiation of paw inflammation (paw swelling, histopathological analysis), CIA rats were therapeutically administered FK506 or methotrexate (MTX) from day 15. Therapeutic treatment with FK506 ameliorated spontaneous locomotor activity without suppressing paw inflammation in CIA rats from day 27. FK506 also improved hyperalgesia and grip strength from day 27. Therapeutic treatment with MTX did not improve spontaneous locomotor activity, and simultaneously did not recover hyperalgesia or grip strength in CIA rats. Our results indicate that spontaneous locomotor activity in CIA rats correlates mainly with hyperalgesia and muscle strength, but not paw inflammation, implying that therapeutic treatment with FK506 ameliorates spontaneous locomotor activity via improvement of hyperalgesia and muscle strength in CIA rats.

Calcineurin inhibitors exert rapid reduction of inflammatory pain in rat adjuvant-induced arthritis

1. FK506 and cyclosporin A (CsA) are immunosuppressive drugs, that specifically inhibit T-cell activation via calcineurin inhibition. This study was undertaken to investigate whether calcineurin inhibitors exert analgesic actions in rat adjuvant-induced arthritis (AIA), an animal model of rheumatoid arthritis (RA). 2. AIA was induced in female Lewis rats. Single doses of FK506 and CsA were orally administered to arthritic rats 17 days after arthritis induction. Intensity of hyperalgesia was assessed by measuring the pain threshold of hind paws. Tumor necrosis factor (TNF)-alpha, IL-1beta and PGE(2) levels in paw extracts were determined by ELISA. TNF activity was measured by L929 cell cytotoxicity assay. IL-1beta and cyclooxygenase (COX) mRNA expression in arthritic paws were measured by RT-PCR. 3. Single doses of FK506 and CsA markedly reduced joint hyperalgesia 24 h after drug administration, without affecting inflammation in an advanced stage of AIA. 4. The calcineurin inhibitors partially reduced the elevated level of TNF-alpha in arthritic paws, however, the analgesic effects of these drugs were not associated with the reduction in TNF-alpha level. 5. Moreover, treatment with anti-rat TNF-alpha antibody did not affect the hyperalgesia, when TNF-alpha activity was suppressed in arthritic paws by that treatment. 6. Both calcineurin inhibitors reduced the elevated level of IL-1beta in arthritic paws to a normal level, 24 h after drug administration. 7. FK506 reduced IL-1beta and COX-2 mRNA expression and PGE(2) level in arthritic paws. 8 In conclusion, calcineurin inhibitors rapidly reduce joint hyperalgesia probably by downregulating IL-1beta, but not TNF-alpha, in AIA. Our findings may provide a new strategy for the treatment of pain in RA.

Role of endogenous glucocorticoids in hyperalgesia and edema in old arthritic rats

We compared the intensity and frequency of arthritis in old (8-12 months, N = 12) and juvenile (2 months, N = 10) rats and determined the role played by adrenal glands in this disorder. Arthritis was induced by subcutaneous injection of Mycobacterium butyricum at the base of the tail of female Holtzman rats at day zero. Paw edema and hyperalgesia were monitored from day zero to day 21 after induction as signs of arthritis development. Some (N = 11) old animals were adrenalectomized bilaterally and treated with dexamethasone or celecoxib immediately following surgery. All bilaterally adrenalectomized old animals became susceptible to arthritis and the onset of disease was shortened from the 10th to the 5th day. Hyperalgesia and paw edema responses were less frequent in older animals (50 and 25% compared to control juvenile rats, respectively), although old responder animals showed responses of similar intensity to those of their juvenile counterparts: by the 14th day the data for hyperalgesia were juvenile = 0.8 +/- 0.07/old = 0.8 +/- 0.09, and for paw edema juvenile = 56.6 +/- 6.04/old = 32.24 +/- 12.7, reported as delta% increase in paw edema. Chronic treatment of adrenalectomized old animals with dexamethasone (0.01 or 0.1 mg/kg) but not celecoxib (3 mg/kg), once daily for 21 days by gavage, abolished the effects of adrenalectomy, in particular those related to the hyperalgesia response (old = 0.95 +/- 0.03/dexamethasone = 0 +/- 0; 14th day), thus suggesting a specific participation of circulating corticosteroids in the modulation of pain in old arthritic rats.

Anti-inflammatory and analgesic effects of the phosphodiesterase 4 inhibitor rolipram in a rat model of arthritis

There has been much interest in strategies which modulate tumour necrosis factor-alpha (TNF-alpha) levels and/or function in rheumatoid arthritis. The elevation of intracellular levels of cyclic AMP in leukocytes by phosphodiesterase 4 inhibitors is accompanied by significant inhibition of the production of TNF-alpha. Nevertheless, these drugs may enhance the hyperalgesia induced by a range of inflammatory mediators, including TNF-alpha. In the present study, we examined the effects of the phosphodiesterase 4 inhibitor rolipram on the local inflammatory infiltrate and hyperalgesia in a rat model of adjuvant-induced arthritis. Rolipram (3 mg/kg) was administered by oral gavage from day 10 to 14 after disease induction. Pretreatment with rolipram abrogated oedema formation and significantly inhibited hyperalgesia. Histopathological analysis revealed a marked inhibition of cellular influx as well as bone and cartilage destruction. Serum and local TNF-alpha levels were suppressed in treated animals whereas there were little changes in interleukin-1beta levels. Although cyclic AMP elevating agents may affect nociceptor threshold to increase the hyperalgesic responses acutely, they also possess significant anti-inflammatory activity, which may hinder local mediator release and/or action. The anti-inflammatory effects of rolipram predominate during this chronic arthritis model in the rat.