Multifunctional, JNK-inhibiting nanotherapeutics for augmented elastic matrix regenerative repair in aortic aneurysms

Abstract

Growth of abdominal aortic aneurysms (AAA), localized aortal wall expansions, is driven by the disruption and subsequent loss of aortal wall elastic fibers by matrix metalloproteases (MMPs). Since elastic fibers do not naturally regenerate or repair, arresting/reversing AAA growth has not been possible. Previously, we showed utility of doxycycline (DOX), an MMP inhibitor drug, to stimulate elastic matrix neoassembly and crosslinking at low microgram per milliliter doses in addition to inhibiting MMPs. We currently show in aneurysmal smooth muscle cell (SMC) cultures that effects of exogenous DOX in this dose range are linked to its upregulation of transforming growth factor beta (TGF-β1) via its inhibition of the regulatory protein c-Jun-N-terminal kinase 2 (JNK 2). We have identified a DOX dose range that stimulates elastogenesis and crosslinking without adversely impacting cell viability. Using JNK 2 inhibition as a metric for pro-regenerative matrix effects of DOX, we further demonstrate that sustained, steady-state release of DOX at the useful dose, from poly(ethylene glycol)-poly(lactic glycolic acid) nanoparticles (NPs), provides pro-elastogenic and anti-proteolytic effects that could potentially be more pronounced than that of exogenous DOX. We attribute these outcomes to previously determined synergistic effects provided by cationic amphiphile groups functionalizing the polymer NP surface. Released DOX inhibited expression and phosphorylation of JNK to likely increase expression of TGF-β1, which is known to increase elastogenesis and lysyl oxidase-mediated crosslinking of elastic matrix. Our results suggest that JNK inhibition is a useful metric to assess pro-elastic matrix regenerative effects and point to the combinatorial regenerative benefits provided by DOX and cationic-functionalized NPs.

A Novel Hybrid Drug Delivery System for Treatment of Aortic Aneurysms

“…Since AAAs are predominately localized to a limited site on the aorta, it is reasonable to strive for local drug delivery to increase the therapeutic efficacy and reduce systemic side effects. Recently, several studies have demonstrated the efficacy of nanoparticle therapies for treating AAAs in rodent models [ 24 , 25 , 26 , 27 , 28 ]. Those approaches could provide attractive strategies for inhibiting AAA progression.…”

Matrix remodeling in chronic lung diseases

“…For example, doxycycline (DOX), a broad-spectrum MMP inhibitor, has been used to inhibit elastin breakdown and allow regeneration and repair of elastin in models of aortic aneurysm [132, 133]. DOX has also been shown to inhibit c-Jun-N-terminal kinase 2 (JNK 2), which promotes TGF-β1 expression and elastogenesis mediated by the lysyl oxidase crosslinking of elastin [134]. Because systemic MMP inhibition can prevent normal ECM turnover in healthy tissues [135–137], efforts are now being directed towards local delivery of MMP inhibitors.…”

Nanotherapeutics to Modulate the Compromised Micro-Environment for Lung Cancers and Chronic Obstructive Pulmonary Disease

“…Adult cells are incapable of regenerating or repairing the elastic matrix as they poorly synthesize elastin precursors and are unable to polymerize and crosslink these precursors into functional, directionally oriented three-dimensional fibers; thus, there is a need to develop tissue engineering strategies to regenerate and repair the elastic matrix. Tangentially related, recent efforts in this author’s lab have been successful in augmenting elastic matrix neoassembly by aneurysmal SMCs utilizing doxycycline (DOX)-releasing polymeric NPs toward regressing abdominal aortic aneurysms ( Sivaraman and Ramamurthi, 2013 ; Camardo et al, 2017 ). For example, the positive charge and hydrocarbon chains presented by cationic amphiphiles functionalized on these NPs simultaneously recapitulate the charge and steric hinderance-mediated anti-MMP effects of natural tissue inhibitors of MMPs (TIMPs) and also mimic the surface of low density lipoproteins (LDL), which electrostatically attract and augment activity of anionic LOX to increase elastic matrix assembly in tissues following their uptake ( Jennewine et al, 2017 ; Sivaraman et al, 2017 ).…”

“…For example, the positive charge and hydrocarbon chains presented by cationic amphiphiles functionalized on these NPs simultaneously recapitulate the charge and steric hinderance-mediated anti-MMP effects of natural tissue inhibitors of MMPs (TIMPs) and also mimic the surface of low density lipoproteins (LDL), which electrostatically attract and augment activity of anionic LOX to increase elastic matrix assembly in tissues following their uptake ( Jennewine et al, 2017 ; Sivaraman et al, 2017 ). Additionally, the long-term, steady-state delivery of DOX from these biodegradable NPs was shown to modulate inflammation by inhibiting MMPs and protecting α-1 antitrypsin, provide anti-oxidant effects, besides stimulating elastic matrix regenerative repair ( Sivaraman and Ramamurthi, 2013 ; Camardo et al, 2017 ). Such approaches utilizing multifunctional NPs could be modified to aid in the regeneration and repair of the elastic matrix in the alveoli and inhibit macrophage polarization from a pro-inflammatory to pro-tumorigenic and pro-angiogenic phenotype ( Hussain, 2016 ).…”