Frataxin deficiency shifts metabolism to promote reactive microglia via glucose catabolism

Immunometabolism investigates the intricate relationship between the immune system and cellular metabolism. This study delves into the consequences of mitochondrial frataxin (FXN) depletion, the primary cause of Friedreich's ataxia (FRDA), a debilitating neurodegenerative condition characterized by impaired coordination and muscle control. By using single-cell RNA sequencing, we have identified distinct cellular clusters within the cerebellum of an FRDA mouse model, emphasizing a significant loss in the homeostatic response of microglial cells lacking FXN. Remarkably, these microglia deficient in FXN display heightened reactive responses to inflammatory stimuli. Furthermore, our metabolomic analyses reveal a shift towards glycolysis and itaconate production in these cells. Remarkably, treatment with butyrate counteracts these immunometabolic changes, triggering an antioxidant response via the itaconate-Nrf2-GSH pathways and suppressing the expression of inflammatory genes. Furthermore, we identify Hcar2 (GPR109A) as a mediator involved in restoring the homeostasis of microglia without FXN. Motor function tests conducted on FRDA mice underscore the neuroprotective attributes of butyrate supplementation, enhancing neuromotor performance. In conclusion, our findings elucidate the role of disrupted homeostatic function in cerebellar microglia in the pathogenesis of FRDA. Moreover, they underscore the potential of butyrate to mitigate inflammatory gene expression, correct metabolic imbalances, and improve neuromotor capabilities in FRDA.

Lipocalin-2 promotes adipose-macrophage interactions to shape peripheral and central inflammatory responses in experimental autoimmune encephalomyelitis

OBJECTIVE

Accumulating evidence suggests that dysfunctional adipose tissue (AT) plays a major role in the risk of developing multiple sclerosis (MS), the most common immune-mediated and demyelinating disease of the central nervous system. However, the contribution of adipose tissue to the etiology and progression of MS is still obscure. This study aimed at deciphering the responses of AT in experimental autoimmune encephalomyelitis (EAE), the best characterized animal model of MS.

RESULTS AND METHODS

We observed a significant AT loss in EAE mice at the onset of disease, with a significant infiltration of M1-like macrophages and fibrosis in the AT, resembling a cachectic phenotype. Through an integrative and multilayered approach, we identified lipocalin2 (LCN2) as the key molecule released by dysfunctional adipocytes through redox-dependent mechanism. Adipose-derived LCN2 shapes the pro-inflammatory macrophage phenotype, and the genetic deficiency of LCN2 specifically in AT reduced weight loss as well as inflammatory macrophage infiltration in spinal cord in EAE mice. Mature adipocytes downregulating LCN2 reduced lipolytic response to inflammatory stimuli (e.g. TNFα) through an ATGL-mediated mechanism.

CONCLUSIONS

Overall data highlighted a role LCN2 in exacerbating inflammatory phenotype in EAE model, suggesting a pathogenic role of dysfunctional AT in MS.

Understanding alkali metal cation affinities of multi-layer guanine quadruplex DNA

To gain better understanding of the stabilizing interactions between metal ions and DNA quadruplexes, dispersion-corrected density functional theory (DFT-D) based calculations were performed on double-, triple- and four-layer guanine tetrads interacting with alkali metal cations. All computations were performed in aqueous solution that mimics artificial supramolecular conditions where guanine bases assemble into stacked quartets as well as biological environments in which telomeric quadruplexes are formed. To facilitate the computations on these significant larger systems, optimization of the DFT description was performed first by evaluating the performance of partial reduced basis sets. Analysis of the stabilizing interactions between alkali cations and the DNA bases in double and triple-layer guanine quadruplex DNA reproduced the experimental affinity trend of the order Li⁺< Rb⁺ < Na⁺ < K⁺. The desolvation and the size of alkali metal cations are thought to be responsible for the order of affinity. Nevertheless, for the alkali metal cation species individually, the magnitude of the bond energy stays equal for binding as first, second or third cation in double, triple and four-layer guanine quadruplexes, respectively. This is the result of an interplay between a decreasingly stabilizing interaction energy and increasingly stabilizing solvation effects, along the consecutive binding events. This diminished interaction energy is the result of destabilizing electrostatic repulsion between the hosted alkali metal cations. This work emphasizes the stabilizing effect of aqueous solvent on large highly charged biomolecules.

Stabilizing solvent effects and electrostatic repulsion are responsible for the constant alkali metal cation affinity in multi-layer guanine quadruplexes.

Reduced fibrinolytic resistance in patients with factor XI deficiency. Evidence of a thrombin-independent impairment of the thrombin-activatable fibrinolysis inhibitor pathway

Essentials Plasma of factor XI-deficient patients (FXI-dp) displays enhanced fibrinolysis. We investigated the role of thrombin activatable fibrinolysis inhibitor (TAFI) in 18 FXI-dp. FXI-dp generated less activated TAFI (TAFIa) on clotting challenge and were resistant to TAFIa. TAFI activation and TAFIa resistance correlated with bleeding score and bleeding phenotype.

SUMMARY

Background Factor XI (FXI) deficiency, a rare disorder with unpredictable bleeding, has been associated with reduced fibrinolytic resistance as a result of abnormal fibrin density. Objective We investigated the involvement of thrombin-activatable fibrinolysis inhibitor (TAFI) in the increased lysability of FXI-deficient (FXI-def) clots and the role of thrombin. Patients/Methods Eighteen patients with FXI deficiency (1-58%) and 17 matched controls were investigated for fibrinolytic resistance to t-PA, thrombin generation, TAFI activation and response to TAFIa. Results When clotting was induced by 0.5 pm tissue factor (TF), FXI-def plasmas displayed less thrombin and TAFIa generation and shorter lysis time than controls. A 100-fold higher TF concentration (to bypass FXI) abolished the difference in thrombin generation but not in lysis time between patients and controls. Normalization of FXI levels by a FXI concentrate increased thrombin generation but had no effect on the lysis time of FXI-def plasma. Moreover, when clots were induced by purified thrombin and high concentrations of FXa inhibitor, FXI-def plasma still generated less TAFIa and displayed a shorter lysis time than controls. Finally, upon TAFIa addition, the lysis time of FXI-def plasma was prolonged significantly less than that of control plasma, suggesting a TAFIa resistance. TAFIa generation and TAFIa resistance were correlated with the bleeding score, displaying a considerable capacity to discriminate between patients with and without bleeding. Conclusions TAFI pathway impairment, largely caused by a hitherto unknown TAFIa resistance, appears to be one main cause of decreased fibrinolytic resistance in FXI deficiency and might be clinically useful for assessing the bleeding risk of FXI-def patients.

The role of alkali metal cations in the stabilization of guanine quadruplexes: why K+ is the best

The desolvation and size of monovalent alkali metal ions are of equal importance for the cation affinity of guanine quadruplexes.

High-dose aprotinin modulates the balance between proinflammatory and anti-inflammatory responses during coronary artery bypass graft surgery

OBJECTIVE

To rule out the effect of high-dose aprotinin in respect to the balance of proinflammatory and anti-inflammatory mediators induced by cardiopulmonary bypass (CPB).

DESIGN

Randomized, double-blind, placebo-controlled study.

SETTING

University-affiliated cardiac center.

PARTICIPANTS

Twenty patients scheduled for coronary artery bypass graft surgery.

INTERVENTIONS

In group A patients (n = 10), high-dose aprotinin was administered (2 x 106 KIU pre-CPB, 2 x 10(6) KIU in prime, 500,000 KIU/hr during CPB). In group C patients (n = 10), placebo was used instead. Proinflammatory interleukin (IL)-6, anti-inflammatory IL-1-receptor antagonist, and clinical parameters were measured 8 times perioperatively. The values are presented as mean +/- SEM.

MEASUREMENTS AND MAIN RESULTS

Four hours after CPB, IL-6 concentration reached the maximum value, being significantly lower in group A patients as compared with group C patients (615 +/- 62 pg/mL v 1,409 +/- 253 pg/mL; p = 0.019). On the first postoperative day, the concentration of IL-6 in group A patients remained lower (219 +/- 24 pg/mL v 526 +/- 123 pg/mL; p = 0.015). In contrast, IL-1-receptor antagonist concentration was higher in group A patients as compared with group C patients after CPB (13,857 +/- 4,264 pg/mL v 5,675 +/- 1,832 pg/mL; p = 0.03). Total postoperative blood loss was lower in group A patients as compared with group C patients (648 +/- 64 mL v 1,284 +/- 183 mL; p = 0.002).

CONCLUSIONS

High-dose aprotinin treatment reduced the inflammatory reaction and postoperative blood loss. The anti-inflammatory reaction was significantly enhanced in these patients, which suggests that the physiologic reaction of the organism to reduce the deleterious effects from CPB is more pronounced by using high-dose aprotinin.

Hemodynamic alterations during massive incisional hernioplasty

BACKGROUND

The operative treatment of a large abdominal incisional hernia increases intra-abdominal pressure (IAP). This study was done to verify if this IAP elevation acts on the cardiocirculatory function.

STUDY DESIGN

Hemodynamic measurements were performed in five patients who underwent massive incisional hernioplasty before and after abdominal wall closure.

RESULTS

Reduction of a large abdominal hernia increases (+226 percent) IAP, which can produce serious hemodynamic alterations, manifested in two patients by a fall of cardiac output (-30 percent), without significant variations of heart rate and arterial pressure. Cardiac output is decreased secondary to decreased venous return, despite the increase in measured central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP).

CONCLUSIONS

During massive incisional hernioplasty, CVP cannot be used as an indicator of venous return to the heart as it reflects a composite of venous filling pressure, pleural pressure, and transmitted IAP. Transmural CVP and PCWP, and not directly measured CVP and PCWP, should be used as clinical indicators of venous return to the heart in this situation.

Atrial fibrillation and infarct area extent in ischemic stroke. A clinical and neuroradiological study in 104 patients

The extent of infarct area (IA) on CT-scan in 104 patients with ischemic stroke (IS) was compared with the presence of atrial fibrillation (AF) and other risk factors (hypertension, dyslipidemia, alcohol abuse). Infarct size was also compared with biological and clinical parameters in acute stage (6-12 h) (blood glucose level, systolic and diastolic arterial pressure, haematocrit, consciousness, clinical picture) and with clinical outcome. Among risk factors, only AF showed a significant correlation with IA extension (p less than .0009). IA correlated also with consciousness (p = .0017), clinical picture (p = .0145) and with clinical outcome (p less than 10(-6). Patients with AF showed a more severe clinical outcome with respect to patients without risk factors. It could be hypothesized that patients with AF have a reduced capacity for increasing or sustaining cerebral blood flow in the acute phase of IS.

[Immunologic changes in chronic pancreatitis]

In 35 patients with chronic pancreatitis, C3, C4, s-immunoglobulins, circulating immunocomplexes and T-lymphocytes were assessed in order to verify whether an immunological role may be postulated in the pathogenesis and/or in the maintenance of the disease. A significant increase of serum IgM together with normal values of C3 and C4 and without circulating immunocomplexes was found. A significant decrease in the total number of lymphocytes as well as in the number and percentage of T-lymphocytes was also documented. These results suggest a possible involvement of immunological (humoral and cellular) processes in maintaining the chronic pancreatic damage.