Optimizing the long-term outcome of renal transplants: opportunities created by sirolimus

Use of Poly Lactic-co-glycolic Acid Nano and Micro Particles in the Delivery of Drugs Modulating Different Phases of Inflammation

Chronic inflammation contributes to the pathogenesis of many diseases, including apparently unrelated conditions such as metabolic disorders, cardiovascular diseases, neurodegenerative diseases, osteoporosis, and tumors, but the use of conventional anti-inflammatory drugs to treat these diseases is generally not very effective given their adverse effects. In addition, some alternative anti-inflammatory medications, such as many natural compounds, have scarce solubility and stability, which are associated with low bioavailability. Therefore, encapsulation within nanoparticles (NPs) may represent an effective strategy to enhance the pharmacological properties of these bioactive molecules, and poly lactic-co-glycolic acid (PLGA) NPs have been widely used because of their high biocompatibility and biodegradability and possibility to finely tune erosion time, hydrophilic/hydrophobic nature, and mechanical properties by acting on the polymer's composition and preparation technique. Many studies have been focused on the use of PLGA-NPs to deliver immunosuppressive treatments for autoimmune and allergic diseases or to elicit protective immune responses, such as in vaccination and cancer immunotherapy. By contrast, this review is focused on the use of PLGA NPs in preclinical in vivo models of other diseases in which a key role is played by chronic inflammation or unbalance between the protective and reparative phases of inflammation, with a particular focus on intestinal bowel disease; cardiovascular, neurodegenerative, osteoarticular, and ocular diseases; and wound healing.

Application of PLGA nano/microparticle delivery systems for immunomodulation and prevention of allotransplant rejection

INTRODUCTION

Allograft transplantation is an effective end-point therapy to replace the function of an impaired organ. The main problem associated with allotransplantation is the induction of immune responses that results in acute and chronic graft rejection. To modulate the response of the immune system, transplant recipients generally take high dose immunosuppressant drugs for life. These drugs are associated with serious side effects such as infection with opportunistic pathogens and the development of neoplasia.

AREAS COVERED

We reviewed the obstacles to successful transplantation and PLGA-based strategies to reduce immune-mediated allograft rejection.

EXPERT OPINION

Biomaterial-based approaches using micro- and nanoparticles such as poly (lactic-co-glycolic acid) (PLGA) can be used to achieve controlled release of drugs. This approach decreases the required effective dose of drugs and enables local delivery of these agents to specific tissues and cells, whilst decreasing systemic effects.

Mycophenolate mofetil-based immunosuppressive minimization and withdrawal strategies in renal transplantation: possible risks and benefits

The toxicity of standard triple-therapy immunosuppressive regimens has been identified as a possible factor in the failure to extend long-term renal allograft survival despite a continued decline of acute rejection rates. The result has been increasing focus on the use of mycophenolate mofetil-based, low-toxicity immunosuppressive regimens, which have been shown in randomized studies to have the potential to improve long-term graft survival. This Clinical Update discusses the likely risks and benefits for switching the immunosuppressive regimen in clinical practice.

Rapamycin decreases leukocyte migration in vivo and effectively reduces experimentally induced chronic colitis

BACKGROUND

Immunosuppressive calcineurin inhibitors, like cyclosporine (CsA), can be used for the clinical management of severe ulcerative colitis. However, patients treated with CsA are at a risk for developing kidney failure and may be more susceptible to colon cancer. Furthermore, severe neurotoxicity and hypertension are common problems. To avoid the side effects of CsA, new immunosuppressive drugs to treat colitis are needed. The aim of the present study was to test the immunosuppressive mammalian target of rapamycin inhibitor rapamycin in an experimental model of chronic colitis and to compare its effectiveness with CsA.

METHODS

Chronic colitis was established in Balb/c mice after four feeding cycles of dextran sodium sulfate. Because leukocyte recruitment to sites of intestinal inflammation is crucial for the development of chronic colitis, intravital microscopy was used to study the effect of rapamycin and CsA on leukocyte-endothelium interactions and leukocyte extravasation. To assess the degree of colitis, histological sections were evaluated.

RESULTS

Both rapamycin and cyclosporine effectively reduced leukocyte sticking (>60%) in submucosal venules, as compared to controls. Furthermore, rapamycin, but not CsA, reduced (>35%) leukocyte extravasation in the mucosa. Both rapamycin and CsA treatments significantly improved the histologic inflammation score.

CONCLUSION

Our in vivo results demonstrate that rapamycin reduces leukocyte sticking and extravasation during chronic colitis induction and proves to be as effective as CsA at reducing experimental chronic colitis. These results support the use of rapamycin in clinical trials to avoid serious side effects of CsA therapy in chronic colitis patients.

Rapamycin worsens renal function and intratubular cast formation in protein overload nephropathy

BACKGROUND

Rapamycin (sirolimus) is associated with functional nephrotoxicity in some patients with nephrotic glomerular diseases but the pathophysiologic mechanisms are not known. This study investigated the effects of rapamycin on renal function and structure in protein overload nephropathy.

METHODS

Rats with protein overload nephropathy [induced by bovine serum albumin (BSA), 2.1 g by daily intraperitoneal injection, day 0 to day 3] received daily intraperitoneal injections of either vehicle [dimethyl sulfoxide (DMSO)], rapamycin (0.2 mg/kg, an inhibitor of mammalian target of rapamycin), or roscovitine (3.5 mg/kg, a small molecule cyclin-dependent kinase inhibitor) (N= 9 each) from day -3 to day 3.

RESULTS

In protein overload nephropathy, rapamycin caused severe acute renal failure and mild hypercholesterolemia (both P < 0.05). Rapamycin dramatically increased intratubular cast formation, and proximal tubular epithelial cells were swollen and engorged with increased cytoplasmic protein droplets. The number of 5-bromo-2'-deoxyuridine (BrdU)-positive tubular epithelial cells increased by more than 20-fold on day 3 in protein overload nephropathy, and this was attenuated by 65% with rapamycin (P < 0.05), whereas roscovitine was ineffective. Rapamycin increased the protein expression of p27(kip1) in tubular epithelial cells, but did not alter D-type cyclin expression or apoptosis.

CONCLUSION

Rapamycin caused a specific pattern of acute renal injury characterized by increased intratubular cast formation in protein overload nephropathy. This could be due to disruption of a potentially important compensatory mechanism in nephrotic glomerular diseases involving tubular epithelial cell protein endocytosis and proliferation.

Calcineurin inhibitor withdrawal from sirolimus-based therapy in kidney transplantation: a systematic review of randomized trials

Calcineurin inhibitor (CNI) withdrawal has been used as a strategy to improve renal allograft function, however, it also carries risk of acute rejection. We conducted a systematic review of randomized trials that involved CNI withdrawal from a sirolimus-based immunosuppressive regimen. The search strategy yielded six trials (n = 1047 patients) reported in eight publications. CNI withdrawal from sirolimus-based therapy, was associated with an increased risk of acute rejection (risk difference, 6%; 95% CI 2-10%, p = 0.002) but a higher creatinine clearance (mean difference, 7.49 mL/min; 95% CI 5.08-9.89 mL/min, p < 0.00001) at 1 year compared to continued CNI and sirolimus therapy. Graft loss (relative risk, 0.87; 95% CI 0.46-1.64, p = 0.66) and death (relative risk, 0.88; CI 0.40-1.96, p = 0.76) were similar in both groups at 1 year. Hypertension was significantly reduced in the CNI withdrawal group (relative risk, 0.56; 95% CI 0.40-0.78, p = 0.0006). CNI withdrawal from sirolimus-based therapy is associated with an increased risk of acute rejection in the short term with a significant improvement in renal function and a reduction in hypertension. Longer follow-up is needed to determine if these changes will result in a significant improvement in patient and graft survival.