Age-dependent increases in interstitial collagenase and MAP Kinase levels are exacerbated by superoxide dismutase deficiencies

Redox and mTOR-dependent regulation of plasma lamellar calcium influx controls the senescence-associated secretory phenotype

IMPACT STATEMENT

Through its ability to evoke responses from cells in a paracrine fashion, the senescence-associated secretory phenotype (SASP) has been linked to numerous age-associated disease pathologies including tumor invasion, cardiovascular dysfunction, neuroinflammation, osteoarthritis, and renal disease. Strategies which limit the amplitude and duration of SASP serve to delay age-related degenerative decline. Here we demonstrate that the SASP regulation is linked to shifts in intracellular Ca2+ homeostasis and strategies which rescue redox-dependent calcium entry including enzymatic H2O2 scavenging, TRP modulation, or mTOR inhibition block SASP and TRPC6 gene expression. As Ca2+ is indispensable for secretion from both secretory and non-secretory cells, it is exciting to speculate that the expression of plasma lamellar TRP channels critical for the maintenance of intracellular Ca2+ homeostasis may be coordinately regulated with the SASP.

Extracellular matrix roles in cardiorenal fibrosis: Potential therapeutic targets for CVD and CKD in the elderly

Whereas hypertension, diabetes, and dyslipidemia are age-related risk factors for cardiovascular disease (CVD) and chronic kidney disease (CKD), aging alone is an independent risk factor. With advancing age, the heart and kidney gradually but significantly undergo inflammation and subsequent fibrosis, which eventually results in an irreversible decline in organ physiology. Through cardiorenal network interactions, cardiac dysfunction leads to and responds to renal injury, and both facilitate aging effects. Thus, a comprehensive strategy is needed to evaluate the cardiorenal aging network. Common hallmarks shared across systems include extracellular matrix (ECM) accumulation, along with upregulation of matrix metalloproteinases (MMPs) including MMP-9. The wide range of MMP-9 substrates, including ECM components and inflammatory cytokines, implicates MMP-9 in a variety of pathological and age-related processes. In particular, there is strong evidence that inflammatory cell-derived MMP-9 exacerbates cardiorenal aging. This review explores the potential therapeutic targets against CVD and CKD in the elderly, focusing on ECM and MMP roles.

Pathways that Regulate ROS Scavenging Enzymes, and Their Role in Defense Against Tissue Destruction in Periodontitis

Periodontitis, an inflammatory disease that affects the tissues surrounding the teeth, is a common disease worldwide. It is caused by a dysregulation of the host inflammatory response to bacterial infection, which leads to soft and hard tissue destruction. In particular, it is the excessive inflammation in response to bacterial plaque that leads to the release of reactive oxygen species (ROS) from neutrophils, which, then play a critical role in the destruction of periodontal tissue. Generally, ROS produced from immune cells exhibit an anti-bacterial effect and play a role in host defense and immune regulation. Excessive ROS, however, can exert cytotoxic effects, cause oxidative damage to proteins, and DNA, can interfere with cell growth and cell cycle progression, and induce apoptosis of gingival fibroblasts. Collectively, these effects enable ROS to directly induce periodontal tissue damage. Some ROS also act as intracellular signaling molecules during osteoclastogenesis, and can thus also play an indirect role in bone destruction. Cells have several protective mechanisms to manage such oxidative stress, most of which involve production of cytoprotective enzymes that scavenge ROS. These enzymes are transcriptionally regulated via NRF2, Sirtuin, and FOXO. Some reports indicate an association between periodontitis and these cytoprotective enzymes' regulatory axes, with superoxide dismutase (SOD) the most extensively investigated. In this review article, we discuss the role of oxidative stress in the tissue destruction manifest in periodontitis, and the mechanisms that protect against this oxidative stress.

Senescence in chronic allograft nephropathy

Despite increasing numbers of patients on dialysis, the numbers of renal transplants performed yearly have remained relatively static. During the last 50 years, there have been many advances in the pharmacology of prevention of organ rejection. However, most patients will suffer from a slow but steady decline in renal function leading to graft loss. The most common cause of long-term graft loss is chronic allograft nephropathy (CAN). Therefore, elucidating and understanding the mechanisms involved in CAN is crucial for achieving better posttransplant outcomes. It is thought that the development of epithelial to mesenchymal transition (EMT) in proximal tubules is one of the first steps towards CAN, and has been shown to be a result of cellular senescence. Cells undergoing senescence acquire a senescence associated secretory phenotype (SASP) leading to the production of interleukin-1 alpha (IL-1α), which has been implicated in several degenerative and inflammatory processes including renal disease. A central mediator in SASP activation is the production of reactive oxygen species (ROS), which are produced in response to numerous physiological and pathological stimuli. This review explores the connection between SASP and the development of EMT/CAN in an effort to suggest future directions for research leading to improved long-term graft outcomes.

NADPH oxidase is a novel target of delphinidin for the inhibition of UVB-induced MMP-1 expression in human dermal fibroblasts

We investigated the reported antiphotoaging effects of the major anthocyanidin delphidin and sought to identify its specific molecular target during UVB-induced MMP-1 expression. Delphinidin treatment significantly inhibited UVB-induced MMP-1 expression in primary cultured human dermal fibroblasts (HDF), an effect associated with the suppression of MKK4-JNK1/2, MKK3/6-p38 and MEK-ERK1/2 phosphorylation. Further investigation revealed that delphinidin significantly inhibited UVB-induced ROS production and NOX activity. Interestingly, the inhibitory effect of delphinidin on UVB-induced NOX activity was stronger than that of apocynin, a pharmaceutical NOX inhibitor. Fractioned cell analysis results using a Western blot assay showed that this effect occurred through the inhibition of UVB-induced P47(phox) (a NOX subunit) translocation from the cytosol to the membrane. Pull down assays demonstrated that delphinidin binds directly to P47(phox) in vitro. Collectively, our results suggest that delphinidin targets NOX, resulting in the suppression of UVB-induced MMP-1 expression in human dermal fibroblasts.

H2O2 accumulation mediates differentiation capacity alteration, but not proliferative decline, in senescent human fetal mesenchymal stem cells

AIMS

Mesenchymal stem cells (MSCs) with multilineage differentiation capacity and immunomodulatory properties are novel sources for cell therapy. However, in vitro expansion of these rare somatic stem cells leads to senescence, resulting in declines of differentiation and proliferative capacities. We therefore investigated the mechanisms mediating senescence in human fetal MSCs termed placenta-derived multipotent cells (PDMCs).

RESULTS

Long-term cultured PDMCs underwent senescence, with increased levels of hydrogen peroxide (H2O2; a reactive oxygen species), positive β-galactosidase staining, decreased sirtuin-1 expression, increased p21 expression, and cell cycle arrest at the G0/G1 phase. Senescent PDMCs also showed decreased osteogenic capacity. Mechanistically, increased p21 expression and proliferative decline were not due to elevated H2O2 levels nor mediated by p53. Instead, inhibition of protein kinase C (PKC)-α and -β in senescent PDMCs decreased p21 expression and reversed cell cycle arrest. H2O2 was involved in the alteration of differentiation potential, since scavenging of H2O2 restored expression of c-MAF, an osteogenic and age-sensitive transcription factor, and osteogenic capacity in senescent PDMCs.

INNOVATION

Our findings not only show the effects of senescence on MSCs, but also reveal mechanisms involved in mediating decreased proliferation and differentiation capacity. Moreover, targeting increased levels of H2O2 associated with senescence may reverse the decreased osteogenic capacity of senescent MSCs.

CONCLUSION

Our study suggests that the two biological consequences of senescence, differentiation alteration, and proliferative decline, in fetal MSCs are distinctly regulated by the H2O2-c-MAF and PKC-p21 pathways, respectively.

Mitochondrial oxidative stress in aortic stiffening with age: the role of smooth muscle cell function

OBJECTIVE

Age-related aortic stiffness is an independent risk factor for cardiovascular diseases. Although oxidative stress is implicated in aortic stiffness, the underlying molecular mechanisms remain unelucidated. Here, we examined the source of oxidative stress in aging and its effect on smooth muscle cell (SMC) function and aortic compliance using mutant mouse models.

METHODS AND RESULTS

Pulse wave velocity, determined using Doppler, increased with age in superoxide dismutase 2 (SOD2)+/- but not in wild-type, p47phox-/- and SOD1+/- mice. Echocardiography showed impaired cardiac function in these mice. Increased collagen I expression, impaired elastic lamellae integrity, and increased medial SMC apoptosis were observed in the aortic wall of aged SOD2+/- versus wild-type (16-month-old) mice. Aortic SMCs from aged SOD2+/- mice showed increased collagen I and decreased elastin expression, increased matrix metalloproteinase-2 expression and activity, and increased sensitivity to staurosporine-induced apoptosis versus aged wild-type and young (4-month-old) SOD2+/- mice. Smooth muscle α-actin levels were increased with age in SOD2+/- versus wild-type SMCs. Aged SOD2+/- SMCs had attenuated insulin-like growth factor-1-induced Akt and Forkhead box O3a phosphorylation and prolonged tumor necrosis factor-α-induced Jun N-terminal kinase 1 activation. Aged SOD2+/- SMCs had increased mitochondrial superoxide but decreased hydrogen peroxide levels. Finally, dominant-negative Forkhead box O3a overexpression attenuated staurosporine-induced apoptosis in aged SOD2+/- SMCs.

CONCLUSION

Mitochondrial oxidative stress over a lifetime causes aortic stiffening, in part by inducing vascular wall remodeling, intrinsic changes in SMC stiffness, and aortic SMC apoptosis.