Human aging is characterized by a chronic, low-grade inflammation, and this phenomenon has been termed as "inflammaging." Inflammaging is a highly significant risk factor for both morbidity and mortality in the elderly people, as most if not all age-related diseases share an inflammatory pathogenesis. Nevertheless, the precise etiology of inflammaging and its potential causal role in contributing to adverse health outcomes remain largely unknown. The identification of pathways that control age-related inflammation across multiple systems is therefore important in order to understand whether treatments that modulate inflammaging may be beneficial in old people. The session on inflammation of the Advances in Gerosciences meeting held at the National Institutes of Health/National Institute on Aging in Bethesda on October 30 and 31, 2013 was aimed at defining these important unanswered questions about inflammaging. This article reports the main outcomes of this session.

Chronic Inflammation (Inflammaging) and Its Potential Contribution to Age-Associated Diseases

The NOD-like receptor (NLR) family, pyrin domain-containing protein 3 (NLRP3) inflammasome is a component of the inflammatory process, and its aberrant activation is pathogenic in inherited disorders such as cryopyrin-associated periodic syndrome (CAPS) and complex diseases such as multiple sclerosis, type 2 diabetes, Alzheimer's disease and atherosclerosis. We describe the development of MCC950, a potent, selective, small-molecule inhibitor of NLRP3. MCC950 blocked canonical and noncanonical NLRP3 activation at nanomolar concentrations. MCC950 specifically inhibited activation of NLRP3 but not the AIM2, NLRC4 or NLRP1 inflammasomes. MCC950 reduced interleukin-1β (IL-1β) production in vivo and attenuated the severity of experimental autoimmune encephalomyelitis (EAE), a disease model of multiple sclerosis. Furthermore, MCC950 treatment rescued neonatal lethality in a mouse model of CAPS and was active in ex vivo samples from individuals with Muckle-Wells syndrome. MCC950 is thus a potential therapeutic for NLRP3-associated syndromes, including autoinflammatory and autoimmune diseases, and a tool for further study of the NLRP3 inflammasome in human health and disease.

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A small-molecule inhibitor of the NLRP3 inflammasome for the treatment of inflammatory diseases

Most older individuals develop inflammageing, a condition characterized by elevated levels of blood inflammatory markers that carries high susceptibility to chronic morbidity, disability, frailty, and premature death. Potential mechanisms of inflammageing include genetic susceptibility, central obesity, increased gut permeability, changes to microbiota composition, cellular senescence, NLRP3 inflammasome activation, oxidative stress caused by dysfunctional mitochondria, immune cell dysregulation, and chronic infections. Inflammageing is a risk factor for cardiovascular diseases (CVDs), and clinical trials suggest that this association is causal. Inflammageing is also a risk factor for chronic kidney disease, diabetes mellitus, cancer, depression, dementia, and sarcopenia, but whether modulating inflammation beneficially affects the clinical course of non-CVD health problems is controversial. This uncertainty is an important issue to address because older patients with CVD are often affected by multimorbidity and frailty — which affect clinical manifestations, prognosis, and response to treatment — and are associated with inflammation by mechanisms similar to those in CVD. The hypothesis that inflammation affects CVD, multimorbidity, and frailty by inhibiting growth factors, increasing catabolism, and interfering with homeostatic signalling is supported by mechanistic studies but requires confirmation in humans. Whether early modulation of inflammageing prevents or delays the onset of cardiovascular frailty should be tested in clinical trials. Inflammageing is a chronic, pro-inflammatory state that develops with age and is a risk factor for cardiovascular disease, comorbidities, frailty, and death. In this Review, Ferrucci and Fabbri discuss whether therapies to modulate inflammageing can reduce the age-related decline in health.

Inflammageing: chronic inflammation in ageing, cardiovascular disease, and frailty

Ageing is the primary risk factor for most neurodegenerative diseases, including Alzheimer disease (AD) and Parkinson disease (PD). One in ten individuals aged ≥65 years has AD and its prevalence continues to increase with increasing age. Few or no effective treatments are available for ageing-related neurodegenerative diseases, which tend to progress in an irreversible manner and are associated with large socioeconomic and personal costs. This Review discusses the pathogenesis of AD, PD and other neurodegenerative diseases, and describes their associations with the nine biological hallmarks of ageing: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, mitochondrial dysfunction, cellular senescence, deregulated nutrient sensing, stem cell exhaustion and altered intercellular communication. The central biological mechanisms of ageing and their potential as targets of novel therapies for neurodegenerative diseases are also discussed, with potential therapies including NAD+ precursors, mitophagy inducers and inhibitors of cellular senescence.

Ageing as a risk factor for neurodegenerative disease.

The ketone bodies β-hydroxybutyrate (BHB) and acetoacetate (AcAc) support mammalian survival during states of energy deficit by serving as alternative sources of ATP. BHB levels are elevated by starvation, caloric restriction, high-intensity exercise, or the low-carbohydrate ketogenic diet. Prolonged fasting reduces inflammation; however, the impact that ketones and other alternative metabolic fuels produced during energy deficits have on the innate immune response is unknown. We report that BHB, but neither AcAc nor the structurally related short-chain fatty acids butyrate and acetate, suppresses activation of the NLRP3 inflammasome in response to urate crystals, ATP and lipotoxic fatty acids. BHB did not inhibit caspase-1 activation in response to pathogens that activate the NLR family, CARD domain containing 4 (NLRC4) or absent in melanoma 2 (AIM2) inflammasome and did not affect non-canonical caspase-11, inflammasome activation. Mechanistically, BHB inhibits the NLRP3 inflammasome by preventing K(+) efflux and reducing ASC oligomerization and speck formation. The inhibitory effects of BHB on NLRP3 are not dependent on chirality or starvation-regulated mechanisms like AMP-activated protein kinase (AMPK), reactive oxygen species (ROS), autophagy or glycolytic inhibition. BHB blocks the NLRP3 inflammasome without undergoing oxidation in the TCA cycle, and independently of uncoupling protein-2 (UCP2), sirtuin-2 (SIRT2), the G protein-coupled receptor GPR109A or hydrocaboxylic acid receptor 2 (HCAR2). BHB reduces NLRP3 inflammasome-mediated interleukin (IL)-1β and IL-18 production in human monocytes. In vivo, BHB or a ketogenic diet attenuates caspase-1 activation and IL-1β secretion in mouse models of NLRP3-mediated diseases such as Muckle-Wells syndrome, familial cold autoinflammatory syndrome and urate crystal-induced peritonitis. Our findings suggest that the anti-inflammatory effects of caloric restriction or ketogenic diets may be linked to BHB-mediated inhibition of the NLRP3 inflammasome.

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The ketone metabolite β-hydroxybutyrate blocks NLRP3 inflammasome–mediated inflammatory disease

Canonical Nlrp3 Inflammasome Links Systemic Low-Grade Inflammation to Functional Decline in Aging

Integrins are cell adhesion molecules important in cell-cell and cell-extracellular matrix interactions. These interactions are vital to numerous physiological processes including corneal wound healing. This review discusses the structure of integrins as well as the various roles that integrins play in the corneal wound healing process. Integrin profile abnormalities identified in various corneal pathological conditions are also reviewed.

The role of integrins in corneal wound healing

https://digitalcommons.lsu.edu/cgi/viewcontent.cgi?article=4491&context=gradschool_theses

Role of Intraocular Leptospira Infections in the Pathogenesis of Equine Recurrent Uveitis in the Southern United States

Keratomycosis is rarely reported in dogs. The purpose of this study was to review the signalment, clinical characteristics, predisposing factors, and outcome of 11 cases of canine keratomycosis. Medical records of included dogs were reviewed and follow-up information was obtained by re-examination of patients following their initial diagnosis. All 11 patients possessed predisposing factors for fungal keratitis, including an underlying endocrinopathy, pre-existing corneal disease, intraocular surgery, and/or prolonged use of either topical antibiotics or corticosteroids at the time of initial examination. Diagnostic techniques included corneal cytology demonstrating yeast or hyphae in 6 of 11 eyes, and fungal cultures with positive results in 7 of 11 eyes. Fungal organisms isolated included Cladosporium spp. (n = 1), Chrysosporium spp. (n = 1), Curvularia spp. (n = 2), Aspergillus spp. (n = 1), Penicillium spp. (n = 1), and Phialemonium spp. (n = 1). Of the 11 patients, 6 responded to medical management al...

Canine keratomycosis in 11 dogs: a case series (2000-2011).

Dogs diagnosed with sudden acquired retinal degeneration syndrome (SARDS) commonly are presented with concurrent clinical, physical, and historical findings consistent with hyperadreno-corticism (HAC) at the time of vision loss. Thirteen dogs diagnosed with SARDS on the basis of complete ophthalmic examination and extinguished bright-flash electroretinogram were evaluated for steroid hormonal abnormalities. Signalment, case history, physical examination, and clinicopathological findings were recorded. Serum cortisol and sex-hormone concentrations were measured before and after adrenocorticotropic hormone (ACTH) stimulation. Clinical signs of HAC, systemic hypertension, and proteinuria were commonly found in dogs with SARDS. Elevations in one or more sex hormones were found in 11 (85%) of 13 dogs (95% confidence interval [CI] 65% to 100%); cortisol was elevated in nine (69%) of 13 dogs (95% CI 44% to 94%). A minority of dogs (three [23%] of 13; 95% CI 0.2% to 46%) exhibited only an increase in adrenal sex hormones. Only one dog had completely normal ACTH stimulation test results. Symptoms of HAC were associated with abnormal ACTH stimulation results. Routine ACTH stimulation testing to evaluate cortisol and sex hormones, blood pressure screening, and urinalysis are recommended in these animals.

Renee T. Carter

Papers

Canonical Nlrp3 Inflammasome Links Systemic Low-Grade Inflammation to Functional Decline in Aging

The role of integrins in corneal wound healing

Role of Intraocular Leptospira Infections in the Pathogenesis of Equine Recurrent Uveitis in the Southern United States

Canine keratomycosis in 11 dogs: a case series (2000-2011).

Elevations in sex hormones in dogs with sudden acquired retinal degeneration syndrome (SARDS).