Inflammatory Caspase Activity Mediates HMGB1 Release and Differentiation in Myoblasts Affected by Peripheral Arterial Disease

Abstract

Introduction: We previously showed that caspase-1 and -11, which are activated by inflammasomes, mediate recovery from muscle ischemia in mice. We hypothesized that similar to murine models, inflammatory caspases modulate myogenicity and inflammation in ischemic muscle disease. Methods: Caspase activity was measured in ischemic and perfused human myoblasts in response to the NLRP3 and AIM2 inflammasome agonists (nigericin and poly(dA:dT), respectively) with and without specific caspase-1 or pan-caspase inhibition. mRNA levels of myogenic markers and caspase-1 were assessed, and protein levels of caspases-1, -4, -5, and -3 were measured by Western blot. Results: When compared to perfused cells, ischemic myoblasts demonstrated attenuated MyoD and myogenin and elevated caspase-1 mRNA. Ischemic myoblasts also had significantly higher enzymatic caspase activity with poly(dA:dT) (p < 0.001), but not nigericin stimulation. Inhibition of caspase activity including caspase-4/-5, but not caspase-1, blocked activation effects of poly(dA:dT). Ischemic myoblasts had elevated cleaved caspase-5. Inhibition of caspase activity deterred differentiation in ischemic but not perfused myoblasts and reduced the release of HMGB1 from both groups. Conclusion: Inflammatory caspases can be activated in ischemic myoblasts by AIM2 and influence ischemic myoblast differentiation and release of pro-angiogenic HMGB1. AIM2 inflammasome involvement suggests a role as a DNA damage sensor, and our data suggest that caspase-5 rather than caspase-1 may mediate the downstream mediator of this pathway.

miR-1, miR-133a, miR-29b and Skeletal Muscle Fibrosis in Chronic Limb-Threatening Ischaemia.

“…This suggests that the decrease in expression may be due to the loss or atrophy of myo bres and relative over-representation in the cellular mass in the muscle of non-myo bre cell types 68 . Fibrosis is a key feature of muscle pathology in CLTI, and myogenic progenitor cell dysfunction is also observed 12,69,70 . The clinical implications of this remain to be fully understood; however, recent in vivo studies using knockout models, have indicated that Pax7 + myogenic progenitor cells are necessary for regeneration after HLI injury.…”

Vascular regeneration and skeletal muscle repair induced by long-term exposure to SDF-1α derived from engineered mesenchymal stem cells after hindlimb ischemia

“…Indeed, CLI severely damages not only blood vessels but also skeletal muscles, which is another critical component of the limb due to poor nutrient supply, and thus it negatively contributes to amputation and eventual limb loss 6,7 . Nevertheless, current therapeutic regimens for treating PAD have focused only on therapeutic angiogenesis by the induction of blood re ow in ischemic limbs through the delivery of growth factors/proteins, genes, or various types of stem cells to ischemic tissues 8,9 . Despite extensive efforts to induce therapeutic angiogenesis, to date the satisfactory rescue of CLI patients from major limb amputation has not been achieved, which may suggest that vascular regeneration alone is insu cient to achieve complete limb salvage 10,11 .…”

Vascular regeneration and skeletal muscle repair induced by long-term exposure to SDF-1α derived from engineered mesenchymal stem cells after hindlimb ischemia

“…Indeed, CLI severely damages not only blood vessels but also skeletal muscles, which is another critical component of the limb due to poor nutrient supply, and thus, it negatively contributes to amputation and eventual limb loss 6 , 7 . Nevertheless, current therapeutic regimens for treating PAD are focused only on therapeutic angiogenesis by the induction of blood reflow in ischemic limbs through the delivery of growth factors/proteins, genes, or various types of stem cells to ischemic tissues 8 , 9 . Despite extensive efforts to induce therapeutic angiogenesis, to date, satisfactory rescue of CLI patients from major limb amputation has not been achieved, suggesting that vascular regeneration alone is insufficient to achieve complete limb salvage 10 , 11 .…”