Iron scavenging and suppression of collagen cross-linking underlie antifibrotic effects of carnosine in the heart with obesity.

Oral consumption of histidyl dipeptides such as l-carnosine has been suggested to promote cardiometabolic health, although therapeutic mechanisms remain incompletely understood. We recently reported that oral consumption of a carnosine analog suppressed markers of fibrosis in liver of obese mice, but whether antifibrotic effects of carnosine extend to the heart is not known, nor are the mechanisms by which carnosine is acting. Here, we investigated whether oral carnosine was able to mitigate the adverse cardiac remodeling associated with diet induced obesity in a mouse model of enhanced lipid peroxidation (i.e., glutathione peroxidase 4 deficient mice, GPx4+/-), a model which mimics many of the pathophysiological aspects of metabolic syndrome and T2 diabetes in humans. Wild-type (WT) and GPx4+/-male mice were randomly fed a standard (CNTL) or high fat high sucrose diet (HFHS) for 16 weeks. Seven weeks after starting the diet, a subset of the HFHS mice received carnosine (80 mM) in their drinking water for duration of the study. Carnosine treatment led to a moderate improvement in glycemic control in WT and GPx4+/-mice on HFHS diet, although insulin sensitivity was not significantly affected. Interestingly, while our transcriptomic analysis revealed that carnosine therapy had only modest impact on global gene expression in the heart, carnosine substantially upregulated cardiac GPx4 expression in both WT and GPx4+/-mice on HFHS diet. Carnosine also significantly reduced protein carbonyls and iron levels in myocardial tissue from both genotypes on HFHS diet. Importantly, we observed a robust antifibrotic effect of carnosine therapy in hearts from mice on HFHS diet, which further in vitro experiments suggest is due to carnosine's ability to suppress collagen-cross-linking. Collectively, this study reveals antifibrotic potential of carnosine in the heart with obesity and illustrates key mechanisms by which it may be acting.

Combined Blockade of Interleukin-1α and -1ß Signaling Protects Mice from Cognitive Dysfunction after Traumatic Brain Injury.

Diffuse activation of interleukin-1 inflammatory cytokine signaling after traumatic brain injury (TBI) elicits progressive neurodegeneration and neuropsychiatric dysfunction, and thus represents a potential opportunity for therapeutic intervention. Although interleukin (IL)-1α and IL-1ß both activate the common type 1 IL-1 receptor (IL-1RI), they manifest distinct injury-specific roles in some models of neurodegeneration. Despite its potential relevance to treating patients with TBI, however, the individual contributions of IL-1α and IL-1ß to TBI-pathology have not been previously investigated. To address this need, we applied genetic and pharmacologic approaches in mice to dissect the individual contributions of IL-1α, IL-ß, and IL-1RI signaling to the pathophysiology of fluid percussion-mediated TBI, a model of mixed focal and diffuse TBI. IL-1RI ablation conferred a greater protective effect on brain cytokine expression and cognitive function after TBI than did individual IL-1α or IL-1ß ablation. This protective effect was recapitulated by treatment with the drug anakinra, a recombinant naturally occurring IL-1RI antagonist. Our data thus suggest that broad targeting of IL-1RI signaling is more likely to reduce neuroinflammation and preserve cognitive function after TBI than are approaches that individually target IL-1α or IL-1ß signaling.

Acute vitreoretinal trauma and inflammation after traumatic brain injury in mice.

Objective: Limited attention has been given to ocular injuries associated with traumatic brain injury (TBI). The retina is an extension of the central nervous system and evaluation of ocular damage may offer a less-invasive approach to gauge TBI severity and response to treatment. We aim to characterize acute changes in the mouse eye after exposure to two different models of TBI to assess the utility of eye damage as a surrogate to brain injury. Methods: A model of blast TBI (bTBI) using a shock tube was compared to a lateral fluid percussion injury model (LFPI) using fluid pressure applied directly to the brain. Whole eyes were collected from mice 3 days post LFPI and 24 days post bTBI and were evaluated histologically using a hematoxylin and eosin stain. Results: bTBI mice showed evidence of vitreous detachment in the posterior chamber in addition to vitreous hemorrhage with inflammatory cells. Subretinal hemorrhage, photoreceptor degeneration, and decreased cellularity in the retinal ganglion cell layer was also seen in bTBI mice. In contrast, eyes of LFPI mice showed evidence of anterior uveitis and subcapsular cataracts. Interpretation: We demonstrated that variations in the type of TBI can result in drastically different phenotypic changes within the eye. As such, molecular and phenotypic changes in the eye following TBI may provide valuable information regarding the mechanism, severity, and ongoing pathophysiology of brain injury. Because vitreous samples are easily obtained, molecular changes within the eye could be utilized as biomarkers of TBI in human patients.

Deficiency of neuronal nitric oxide synthase (nNOS) worsens alcohol-induced microencephaly and neuronal loss in developing mice.

Previous work conducted in vitro suggests that nitric oxide (NO) protects developing neurons against the toxic effects of alcohol. We tested the hypothesis that neonatal mice carrying a null mutation for neuronal nitric oxide synthase (nNOS), the enzyme which synthesizes NO in neurons, have increased vulnerability to alcohol-induced microencephaly and neuronal loss. Wild-type mice and mutant (nNOS(-/-)) mice received a single intraperitoneal injection of ethanol (0.0, 2.2, 3.3, or 4.4 g/kg) daily over postnatal days (PD) 4-9 and were sacrificed on PD 10. Peak blood alcohol concentrations were approximately 170, 280, and 385 mg/dl for the 2.2, 3.3 and 4.4 g/kg/day treatment groups, respectively, and did not differ significantly between wild-type and nNOS(-/-) strains. Exposure to alcohol induced dose-dependent reductions in total brain weight, forebrain weight and cerebellum weight in both strains of mice. However, the reductions in brain weight were significantly more severe in the nNOS(-/-) mice than in wild type. Quantification of cerebellar neurons revealed that alcohol-induced losses of Purkinje cells and granule cells were both significantly greater in the nNOS(-/-) mice than in wild type. The increased vulnerability of nNOS-deficient neurons to alcohol-induced cell death was confirmed in vitro. Cerebellar granule cell cultures derived from nNOS(-/-) and wild-type mice were exposed for 24 h to 0, 100, 200 or 400 mg/dl ethanol. At each alcohol concentration, the nNOS(-/-) neurons had a significantly greater cell loss than did the wild-type neurons. The results demonstrate that deficiency of nNOS decreases the ability of developing neurons to survive the toxic effects of alcohol. Because NO upregulates intracellular cGMP, which can activate cGMP-dependent protein kinase (PKG), we hypothesize that the NO-cGMP-PKG pathway has a neuroprotective role against alcohol toxicity within the developing brain.

Critical role for glial cells in the propagation and spread of lymphocytic choriomeningitis virus in the developing rat brain.

Inoculation of the neonatal rat with lymphocytic choriomeningitis virus (LCMV) results in the selective infection of several neuronal populations and in focal pathological changes. However, the pathway by which LCMV reaches the susceptible neurons has not been described, and the nature and time course of the pathological changes induced by the infection are largely unknown. This study examined the sequential migration of LCMV in the developing rat brain and compared the pathological changes among infected brain regions. The results demonstrate that astrocytes and Bergmann glia cells are the first cells of the brain parenchyma infected with LCMV and that the virus spreads across the brain principally via contiguous glial cells. The virus then spreads from glial cells into neurons. However, not all neurons are susceptible to infection. LCMV infects neurons in only four specific brain regions: the cerebellum, olfactory bulb, dentate gyrus, and periventricular region. The virus is then cleared from glial cells but persists in neurons. LCMV induces markedly different pathological changes in each of the four infected regions. The cerebellum undergoes an acute and permanent destruction, while the olfactory bulb is acutely hypoplastic but recovers fully with age. Neurons of the dentate gyrus are unaffected in the acute phase but undergo a delayed-onset mortality. In contrast, the periventricular region has neither acute nor late-onset cell loss. Thus, LCMV infects four specific brain regions in the developing brain by spreading from glial cells to neurons and then induces substantially different pathological changes with diverse time courses in each of the four infected regions.