Mitochondrial dysfunction in macrophages promotes inflammation and suppresses repair after myocardial infarction.

Innate immune cells play important roles in tissue injury and repair following acute myocardial infarction (MI). Although reprogramming of macrophage metabolism has been observed during inflammation and resolution phases, the mechanistic link to macrophage phenotype is not fully understood. In this study, we found that myeloid-specific deletion (mKO) of mitochondrial complex I protein, encoded by Ndufs4, reproduced the proinflammatory metabolic profile in macrophages and exaggerated the response to LPS. Moreover, mKO mice showed increased mortality, poor scar formation, and worsened cardiac function 30 days after MI. We observed a greater inflammatory response in mKO mice on day 1 followed by increased cell death of infiltrating macrophages and blunted transition to the reparative phase during post-MI days 3-7. Efferocytosis was impaired in mKO macrophages, leading to lower expression of antiinflammatory cytokines and tissue repair factors, which suppressed the proliferation and activation of myofibroblasts in the infarcted area. Mitochondria-targeted ROS scavenging rescued these impairments, improved myofibroblast function in vivo, and reduced post-MI mortality in mKO mice. Together these results reveal a critical role of mitochondria in inflammation resolution and tissue repair via modulation of efferocytosis and crosstalk with fibroblasts. These findings have potential significance for post-MI recovery as well as for other inflammatory conditions.

Exogenous ANP Treatment Ameliorates Myocardial Insulin Resistance and Protects against Ischemia-Reperfusion Injury in Diet-Induced Obesity.

Increasing evidence suggests natriuretic peptides (NPs) coordinate interorgan metabolic crosstalk. We recently reported exogenous ANP treatment ameliorated systemic insulin resistance by inducing adipose tissue browning and attenuating hepatic steatosis in diet-induced obesity (DIO). We herein investigated whether ANP treatment also ameliorates myocardial insulin resistance, leading to cardioprotection during ischemia-reperfusion injury (IRI) in DIO. Mice fed a high-fat diet (HFD) or normal-fat diet for 13 weeks were treated with or without ANP infusion subcutaneously for another 3 weeks. Left ventricular BNP expression was substantially reduced in HFD hearts. Intraperitoneal-insulin-administration-induced Akt phosphorylation was impaired in HFD hearts, which was restored by ANP treatment, suggesting that ANP treatment ameliorated myocardial insulin resistance. After ischemia-reperfusion using the Langendorff model, HFD impaired cardiac functional recovery with a corresponding increased infarct size. However, ANP treatment improved functional recovery and reduced injury while restoring impaired IRI-induced Akt phosphorylation in HFD hearts. Myocardial ultrastructural analyses showed increased peri-mitochondrial lipid droplets with concomitantly decreased ATGL and HSL phosphorylation levels in ANP-treated HFD, suggesting that ANP protects mitochondria from lipid overload by trapping lipids. Accordingly, ANP treatment attenuated mitochondria cristae disruption after IRI in HFD hearts. In summary, exogenous ANP treatment ameliorates myocardial insulin resistance and protects against IRI associated with mitochondrial ultrastructure modifications in DIO. Replenishing biologically active NPs substantially affects HFD hearts in which endogenous NP production is impaired.

URAT1-selective inhibition ameliorates insulin resistance by attenuating diet-induced hepatic steatosis and brown adipose tissue whitening in mice.

OBJECTIVE: Accumulating evidence indicates that high uric acid (UA) is strongly associated with obesity and metabolic syndrome and drives the development of nonalcoholic fatty liver disease (NAFLD) and insulin resistance. Although urate transporter-1 (URAT1), which is primarily expressed in the kidneys, plays a critical role in the development of hyperuricemia, its pathophysiological implication in NAFLD and insulin resistance remains unclear. We herein investigated the role and functional significance of URAT1 in diet-induced obese mice. METHODS: Mice fed a high-fat diet (HFD) for 16-18 weeks or a normal-fat diet (NFD) were treated with or without a novel oral URAT1-selective inhibitor (dotinurad [50 mg/kg/day]) for another 4 weeks. RESULTS: We found that URAT1 was also expressed in the liver and brown adipose tissue (BAT) other than the kidneys. Dotinurad administration significantly ameliorated HFD-induced obesity and insulin resistance. HFD markedly induced NAFLD, which was characterized by severe hepatic steatosis as well as the elevation of serum ALT activity and tissue inflammatory cytokine genes (chemokine ligand 2 (Ccl2) and tissue necrosis factor α (TNFα)), all of which were attenuated by dotinurad. Similarly, HFD significantly increased URAT1 expression in BAT, resulting in lipid accumulation (whitening of BAT), and increased the production of tissue reactive oxygen species (ROS), which were reduced by dotinurad via UCP1 activation. CONCLUSIONS: In conclusion, a novel URAT1-selective inhibitor, dotinurad, ameliorates insulin resistance by attenuating hepatic steatosis and promoting rebrowning of lipid-rich BAT in HFD-induced obese mice. URAT1 serves as a key regulator of the pathophysiology of metabolic syndrome and may be a new therapeutic target for insulin-resistant individuals, particularly those with concomitant NAFLD.

Successful treatment of pulmonary hypertension following hematopoietic stem cell transplant with a single oral tadalafil: a case report.

A 46-year-old man who had undergone hematopoietic stem cell transplant twice because of acute lymphoblastic leukemia with recurrence presented with dyspnea, leading to a diagnosis of pulmonary arterial hypertension which was quickly and effectively treated with the phosphodiesterase type 5 inhibitor tadalafil. To our knowledge, pulmonary arterial hypertension related to hematologic malignancies requiring hematopoietic stem cell transplant is rarely reported. Importantly, the present case suggests that early diagnosis and treatment with a pulmonary vasodilator, such as tadalafil, can greatly decrease pulmonary vascular resistance in patients with severe pulmonary arterial hypertension after hematopoietic stem cell transplant and can then improve other symptoms. Accordingly, pulmonary vascular disease should be considered if respiratory symptoms develop following hematopoietic stem cell transplant, because treatment with pulmonary vasodilator may lead to significant improvement in pulmonary arterial hypertension.

A novel TSC1 variant associated with tuberous sclerosis and sacrococcygeal teratoma.

Tuberous sclerosis complex (TSC) is an autosomal dominant disease associated with tumors and malformed tissues in the brain and other vital organs. We report a novel de novo frameshift variant of the TSC1 gene (c.434dup;p. Ser146Valfs*8) in a child with TSC who initially presented with a sacral teratoma. This previously unreported association between TSC and teratoma has broad implications for the pathophysiology of embryonic tumors and mechanisms underlying cellular differentiation.

Hyperexcitability of the local cortical circuit in mouse models of tuberous sclerosis complex.

Tuberous sclerosis complex (TSC) is a neurogenetic disorder associated with epilepsy, intellectual disabilities, and autistic behaviors. These neurological symptoms result from synaptic dysregulations, which shift a balance between excitation and inhibition. To decipher the synaptic substrate of hyperexcitability, we examined pan-neuronal Tsc1 knockout mouse and found a reduction in surface expression of a GABA receptor (GABAR) subunit but not AMPA receptor (AMPAR) subunit. Using electrophysiological recordings, we found a significant reduction in the frequency of GABAR-mediated miniature inhibitory postsynaptic currents (GABAR-mIPSCs) but not AMPAR-mediated miniature excitatory postsynaptic currents (AMPAR-mEPSCs) in layer 2/3 pyramidal neurons. To determine a subpopulation of interneurons that are especially vulnerable to the absence of TSC1 function, we also analyzed two strains of conditional knockout mice targeting two of the prominent interneuron subtypes that express parvalbumin (PV) or somatostatin (SST). Unlike pan-neuronal knockout mice, both interneuron-specific Tsc-1 knockout mice did not develop spontaneous seizures and grew into adults. Further, the properties of AMPAR-mEPSCs and GABAR-mIPSCs were normal in both Pv-Cre and Sst-Cre x Tsc1fl/fl knockout mice. These results indicate that removal of TSC1 from all neurons in a local cortical circuit results in hyperexcitability while connections between pyramidal neurons and interneurons expressing PV and SST are preserved in the layer 2/3 visual cortex. Our study suggests that another inhibitory cell type or a combination of multiple subtypes may be accountable for hyperexcitability in TSC.

Multiple Critical Periods for Rapamycin Treatment to Correct Structural Defects in Tsc-1-Suppressed Brain.

Tuberous sclerosis complex (TSC) is an autosomal dominant neurogenetic disorder affecting the brain and other vital organs. Neurological symptoms include epilepsy, intellectual disability, and autism. TSC is caused by a loss-of-function mutation in the TSC1 or TSC2 gene. These gene products form a protein complex and normally suppress mammalian target of rapamycin (mTOR) activity. mTOR inhibitors have been used to treat subependymal glioma (SEGA) that is a brain tumor characteristic of TSC. However, neuropathology of TSC also involves dysregulated cortical circuit formation including neuronal migration, axodendritic differentiation, and synapse formation. It is currently unknown to what extent mTOR signaling inhibitors correct an alteration in neuronal morphology that have already formed prior to the treatment. Here, we address the efficacy of rapamycin treatment on neuronal migration and dendrite formation. Using in utero electroporation, we suppressed Tsc1 expression in a fraction of neuronal progenitor cells during the fetal period. In embryonic brain slices, we found that more Tsc1-suppressed cells remained within the periventricular zone, and rapamycin treatment facilitated neuronal migration. Postnatally, Tsc1-suppressed pyramidal neurons showed more complex branching of basal dendrites and a higher spine density at postnatal day (P) 28. Aberrant arborization was normalized by rapamycin administration every other day between P1 and P13 but not P15 and P27. In contrast, abnormal spine maturation improved by rapamycin treatment between P15 and P27 but not P1 and P13. Our results indicate that there are multiple critical windows for correcting different aspects of structural abnormalities in TSC, and the responses depend on the stage of neuronal circuit formation. These data warrant a search for an additional therapeutic target to treat neurological symptoms of TSC.

BDNF induces transport of PSD-95 to dendrites through PI3K-AKT signaling after NMDA receptor activation.

The N-methyl-D-aspartate receptor (NMDAR), brain-derived neurotrophic factor (BDNF), postsynaptic density protein 95 (PSD-95) and phosphatidylinositol 3-kinase (PI3K) have all been implicated in long-term potentiation. Here we show that these molecules are involved in a single pathway for synaptic potentiation. In visual cortical neurons in young rodents, the neurotrophin receptor TrkB is associated with PSD-95. When BDNF is applied to cultured visual cortical neurons, PSD-95-labeled synaptic puncta enlarge, and fluorescent recovery after photobleaching (FRAP) reveals increased delivery of green fluorescent protein-tagged PSD-95 to the dendrites. The recovery of fluorescence requires TrkB, signaling through PI3K and the serine-threonine kinase Akt, and an intact Golgi apparatus. Stimulation of NMDARs mimics the PSD-95 trafficking that is induced by BDNF but requires active BDNF and PI3K. Furthermore, local dendritic contact with a BDNF-coated microsphere induces PSD-95 FRAP throughout the dendrites of the stimulated neuron, suggesting that this mechanism induces rapid neuron-wide synaptic increases in PSD-95 and refinement whenever a few robust inputs activate the NMDAR-BDNF-PI3K pathway.

Fas-Fas ligand system as a possible mediator of spermatogenic cell apoptosis in human maturation-arrested testes.

To elucidate the mechanism of maturation arrest, known as one of the male infertility, we addressed whether germ cell apoptosis occurs during maturation arrest, and if so, whether Fas and Fas ligand expressions are involved in the apoptosis. By electron microscopy and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL), typical apoptotic features were frequently found around the spermatocytic stage in maturation arrest, compared to that in normal testes. When paraffin-embedded sections reacted with anti-Fas antiserum, staining for Fas was found in the plasma membranes of spermatocytes in the maturation-arrested testes, while no positive spermatogenic cells were seen in the normal testes. On the other hand, positive immunostaining for Fas ligand was restricted to Sertoli cells in the maturation-arrested testes as well as in the normal testes, although the intensity of staining for Fas ligand in normal testicular Sertoli cells was much weaker than that of maturation-arrested ones. Thus, these findings demonstrate that "maturation arrest" is characterized by frequent apoptosis of spermatocytes, and that Fas and Fas ligand staining are associated with a high frequency of apoptosis.