Can LIGO Detect Nonannihilating Dark Matter?

Dark matter (DM) from the galactic halo can accumulate in neutron stars and transmute them into sub-2.5M_{⊙} black holes if the dark matter particles are heavy, stable, and have interactions with nucleons. We show that nondetection of gravitational waves from mergers of such low-mass black holes can constrain the interactions of nonannihilating dark matter particles with nucleons. We find benchmark constraints with LIGO O3 data, viz., σ_{χn}≥O(10^{-47}) cm^{2} for bosonic DM with m_{χ}∼PeV (or m_{χ}∼GeV, if they can Bose-condense) and ≥O(10^{-46}) cm^{2} for fermionic DM with m_{χ}∼10^{3} PeV. These bounds depend on the priors on DM parameters and on the currently uncertain binary neutron star merger rate density. However, with increased exposure by the end of this decade, LIGO will probe cross sections that are many orders of magnitude below the neutrino floor and completely test the dark matter solution to missing pulsars in the Galactic center, demonstrating a windfall science case for gravitational wave detectors as probes of particle dark matter.

α-Ketoglutarate Inhibits Thrombosis and Inflammation by Prolyl Hydroxylase-2 Mediated Inactivation of Phospho-Akt.

BACKGROUND: Phospho-Akt1 (pAkt1) undergoes prolyl hydroxylation at Pro125 and Pro313 by the prolyl hydroxylase-2 (PHD2) in a reaction decarboxylating α-ketoglutarate (αKG). We investigated whether the αKG supplementation could inhibit Akt-mediated activation of platelets and monocytes, in vitro as well as in vivo, by augmenting PHD2 activity. METHODS: We treated platelets or monocytes isolated from healthy individuals with αKG in presence of agonists in vitro and assessed the signalling molecules including pAkt1. We supplemented mice with dietary αKG and estimated the functional responses of platelets and monocytes ex vivo. Further, we investigated the impact of dietary αKG on inflammation and thrombosis in lungs of mice either treated with thrombosis-inducing agent carrageenan or infected with SARS-CoV-2. FINDINGS: Octyl αKG supplementation to platelets promoted PHD2 activity through elevated intracellular αKG to succinate ratio, and reduced aggregation in vitro by suppressing pAkt1(Thr308). Augmented PHD2 activity was confirmed by increased hydroxylated-proline and enhanced binding of PHD2 to pAkt in αKG-treated platelets. Contrastingly, inhibitors of PHD2 significantly increased pAkt1 in platelets. Octyl-αKG followed similar mechanism in monocytes to inhibit cytokine secretion in vitro. Our data also describe a suppressed pAkt1 and reduced activation of platelets and leukocytes ex vivo from mice supplemented with dietary αKG, unaccompanied by alteration in their number. Dietary αKG significantly reduced clot formation and leukocyte accumulation in various organs including lungs of mice treated with thrombosis-inducing agent carrageenan. Importantly, in SARS-CoV-2 infected hamsters, we observed a significant rescue effect of dietary αKG on inflamed lungs with significantly reduced leukocyte accumulation, clot formation and viral load alongside down-modulation of pAkt in the lung of the infected animals. INTERPRETATION: Our study suggests that dietary αKG supplementation prevents Akt-driven maladies such as thrombosis and inflammation and rescues pathology of COVID19-infected lungs. FUNDING: Study was funded by the Department of Biotechnology (DBT), Govt. of India (grants: BT/PR22881 and BT/PR22985); and the Science and Engineering Research Board, Govt. of India (CRG/000092).

Interplay between hypoxia and inflammation contributes to the progression and severity of respiratory viral diseases.

History of pandemics is dominated by viral infections and specifically respiratory viral diseases like influenza and COVID-19. Lower respiratory tract infection is the fourth leading cause of death worldwide. Crosstalk between resultant inflammation and hypoxic microenvironment may impair ventilatory response of lungs. This reduces arterial partial pressure of oxygen, termed as hypoxemia, which is observed in a section of patients with respiratory virus infections including SARS-CoV-2 (COVID-19). In this review, we describe the interplay between inflammation and hypoxic microenvironment in respiratory viral infection and its contribution to disease pathogenesis.

Gain-of-function Tibetan PHD2D4E;C127S variant suppresses monocyte function: A lesson in inflammatory response to inspired hypoxia.

BACKGROUND: We have previously described an evolutionarily selected Tibetan prolyl hydroxylase-2 (PHD2D4E;C127S) variant that degrades the hypoxia-inducible factor (HIFα) more efficiently and protects these highlanders from hypoxia-triggered elevation in haemoglobin concentration. High altitude is known to cause acute mountain sickness (AMS) and high-altitude pulmonary edema (HAPE) in a section of rapidly ascending non-acclimatised lowlanders. These morbidities are often accompanied by inflammatory response and exposure to hypobaric hypoxia is presumed to be the principal causative agent. We have investigated whether PHD2D4E;C127S variant is associated with prevention of hypoxia-mediated inflammatory milieu in Tibetan highlanders and therefore identify a potential target to regulate inflammation. METHODS: We genotyped the Tibetans using DNA isolated from whole blood. Thereafter immunophenotying was performed on PBMCs from homozygous PHD2D4E;C127S and PHD2WT individuals using flow cytometry. RNA isolated from these individuals was used to evaluate the peripheral level of important transcripts associated with immune as well as hypoxia response employing the nCounter technology. The ex-vivo findings were validated by generating monocytic cell lines (U937 cell line) expressing PHD2D4E;C127S and PHD2WT variants post depletion of endogenous PHD2. We had also collected whole blood samples from healthy travellers and travellers afflicted with AMS and HAPE to evaluate the significance of our ex-vivo and in vitro findings. Hereafter, we also attempted to resolve hypoxia-triggered inflammation in vitro as well as in vivo by augmenting the function of PHD2 using alpha-ketoglutarate (αKG), a co-factor of PHD2. FINDINGS: We report that homozygous PHD2D4E;C127S highlanders harbour less inflammatory and patrolling monocytes in circulation as compared to Tibetan PHD2WT highlanders. In response to in vitro hypoxia, secretion of IL6 and IL1ß from PHD2D4E;C127S monocytes, and their chemotactic response compared to the PHD2WT are compromised, corresponding to the down-modulated expression of related signalling molecules RELA, JUN, STAT1, ATF2 and CXCR4. We verified these functional outcomes in monocytic U937 cell line engineered to express PHD2D4E;C127S and confirmed the down-modulation of the signalling molecules at protein level under hypoxia. In contrast, non-Tibetan sojourners with AMS and HAPE at high altitude (3,600 m above sea level) displayed significant increase in these inflammatory parameters. Our data henceforth underline the role of gain-of-function of PHD2 as the rate limiting factor to harness hyper-activation of monocytes in hypoxic environment. Therefore upon pre-treatment with αKG, we observed diminished inflammatory response of monocytes in vitro and reduction in leukocyte infiltration to the lungs in mice exposed to normobaric hypoxia. INTERPRETATION: Our report suggests that gain-of-function PHD2 D4E;C127S variant can therefore protect against inflammation elicited by hypobaric hypoxia. Augmentation of PHD2 activity therefore may be an important method to alleviate inflammatory response to inspired hypoxia. FUNDING: This study is supported by the Department of Biotechnology, Government of India.

Sensitization of ON-bipolar cells with ambient light activatable multi-characteristic opsin rescues vision in mice.

Gene therapy-based treatment such as optogenetics offers a potentially powerful way to bypass damaged photoreceptors in retinal degenerative diseases and use the remaining retinal cells for functionalization to achieve photosensitivity. However, current approaches of optogenetic treatment rely on opsins that require high intensity light for activation thus adding to the challenge for use as part of a wearable device. Here, we report AAV2 assisted delivery of highly photosensitive multi-characteristic opsin (MCO1) into ON-bipolar cells of mice with retinal degeneration to allow activation by ambient light. Rigorous characterization of delivery efficacy by different doses of AAV2 carrying MCO1 (vMCO1) into targeted cells showed durable expression over 6 months after delivery as measured by reporter expression. The enduring MCO1 expression was correlated with the significantly improved behavioral outcome, that was longitudinally measured by visual water-maze and optomotor assays. The pro/anti-inflammatory cytokine levels in plasma and vitreous humor of the vMCO1-injected group did not change significantly from baseline or control group. Furthermore, biodistribution studies at various time points after injection in animal groups injected with different doses of vMCO1 showed non-detectable vector copies in non-targeted tissues. Immunohistochemistry of vMCO1 transfected retinal tissues showed bipolar specific expression of MCO1 and the absence of immune/inflammatory response. Furthermore, ocular imaging using SD-OCT showed no change in the structural architecture of vMCO1-injected eyes. Induction of ambient light responsiveness to remaining healthy bipolar cells in subjects with retinal degeneration will allow the retinal circuitry to gain visual acuity without requiring an active stimulation device.

Role of Platelet Cytokines in Dengue Virus Infection.

Platelets are anucleated blood cells derived from bone marrow megakaryocytes and play a crucial role in hemostasis and thrombosis. Platelets contain specialized storage organelles, called alpha-granules, contents of which are rich in cytokines such as C-X-C Motif Chemokine Ligand (CXCL) 1/4/7, (C-C motif) ligand (CCL) 5/3, CXCL8 (also called as interleukin 8, IL-8), and transforming growth factor ß (TGF-ß). Activation of platelets lead to degranulation and release of contents into the plasma. Platelet activation is a common event in many viral infections including human immunodeficiency virus (HIV), H1N1 influenza, Hepatitis C virus (HCV), Ebola virus (EBV), and Dengue virus (DENV). The cytokines CXCL8, CCL5 (also known as Regulated on Activation, Normal T Expressed and Secreted, RANTES), tumor necrosis factor α (TNF-α), CXCL1/5 and CCL3 released, promote development of a pro-inflammatory state along with the recruitment of other immune cells to the site of infection. Platelets also interact with Monocytes and Neutrophils and facilitate their activation to release different cytokines which further enhances inflammation. Upon activation, platelets also secrete factors such as CXCL4 (also known as platelet factor, PF4), CCL5 and fibrinopeptides which are critical regulators of replication and propagation of several viruses in the host. Studies suggest that CXCL4 can both inhibit as well as enhance HIV1 infection. Data from our lab show that CXCL4 inhibits interferon (IFN) pathway and promotes DENV replication in monocytes in vitro and in patients significantly. Inhibition of CXCL4 mediated signaling results in increased IFN production and suppressed DENV and JEV replication in monocytes. In this review, we discuss the role of platelets in viral disease progression with a focus on dengue infection.

Nano-enhanced Optical Gene Delivery to Retinal Degenerated Mice.

BACKGROUND: The efficient and targeted delivery of genes and other impermeable therapeutic molecules into retinal cells is of immense importance for the therapy of various visual disorders. Traditional methods for gene delivery require viral transfection, or chemical methods that suffer from one or many drawbacks, such as low efficiency, lack of spatially targeted delivery, and can generally have deleterious effects, such as unexpected inflammatory responses and immunological reactions. METHODS: We aim to develop a continuous wave near-infrared laser-based Nano-enhanced Optical Delivery (NOD) method for spatially controlled delivery of ambient-light-activatable Muti-Characteristic opsin-encoding genes into retina in-vivo and ex-vivo. In this method, the optical field enhancement by gold nanorods is utilized to transiently permeabilize cell membrane, enabling delivery of exogenous impermeable molecules to nanorod-binding cells in laser-irradiated regions. RESULTS AND DISCUSSION: With viral or other non-viral (e.g. electroporation, lipofection) methods, gene is delivered everywhere, causing uncontrolled expression over the whole retina. This will cause complications in the functioning of non-degenerated areas of the retina. In the NOD method, the contrast in temperature rise in laser-irradiated nanorod-attached cells at nano-hotspots is significant enough to allow site-specific delivery of large genes. The in-vitro and in-vivo results using NOD, clearly demonstrate in-vivo gene delivery and functional cellular expression in targeted retinal regions without compromising the structural integrity of the eye or causing immune response. CONCLUSION: The successful delivery and expression of MCO in the targeted retina after in-vivo NOD in the mice models of retinal degeneration opens a new vista for re-photosensitizing retina with geographic atrophies, such as in dry age-related macular degeneration.

Erratum: Publisher's note: Restoring vision in mice with retinal degeneration using multicharacteristic opsin.

[This corrects the article DOI: 10.1117/1.NPh.4.4.041412.].

Restoring vision in mice with retinal degeneration using multicharacteristic opsin.

Retinal degenerative diseases, such as retinitis pigmentosa (RP) and dry age-related macular degeneration, have led to loss of vision in millions of individuals. Currently, no surgical or medical treatment is available, although optogenetic therapies are in clinical development. We demonstrate vision restoration using multicharacteristics opsin (MCO1) in animal models with degenerated retina. MCO1 is reliably delivered to specific retinal cells via intravitreal injection of adeno-associated virus (vMCO1), leading to significant improvement in visually guided behavior conducted using a radial arm water maze. The time to reach the platform and the number of error arms decreased significantly after delivery of MCO1. Notably, the improvement in visually guided behavior was observed even at light intensity levels orders of magnitude lower than that required for channelrhodopsin-2 opsin. Viability of vMCO1-treated retina is not compromised by chronic light exposure. Safe virus-mediated MCO1 delivery has potential for effective gene therapy of diverse retinal degenerations in patients.

Restoring vision in mice with retinal degeneration using multicharacteristic opsin.

Retinal degenerative diseases, such as retinitis pigmentosa (RP) and dry age-related macular degeneration, have led to loss of vision in millions of individuals. Currently, no surgical or medical treatment is available, although optogenetic therapies are in clinical development. We demonstrate vision restoration using multicharacteristics opsin (MCO1) in animal models with degenerated retina. MCO1 is reliably delivered to specific retinal cells via intravitreal injection of adeno-associated virus (vMCO1), leading to significant improvement in visually guided behavior conducted using a radial arm water maze. The time to reach the platform and the number of error arms decreased significantly after delivery of MCO1. Notably, the improvement in visually guided behavior was observed even at light intensity levels orders of magnitude lower than that required for channelrhodopsin-2 opsin. Viability of vMCO1-treated retina is not compromised by chronic light exposure. Safe virus-mediated MCO1 delivery has potential for effective gene therapy of diverse retinal degenerations in patients.

A comparison between volume-controlled ventilation and pressure-controlled ventilation in providing better oxygenation in obese patients undergoing laparoscopic cholecystectomy.

BACKGROUND: The maintenance of oxygenation is a commonly encountered problem in obese patients undergoing laparoscopic cholecystectomy. There is no specific guideline on the ventilation modes for this group of patients. Although several studies have been performed to determine the optimal ventilatory settings in these patients, the answer is yet to be found. The aim of this study was to evaluate the efficacy of pressure-controlled ventilation (PCV) in comparison with volume-controlled ventilation (VCV) for maintaining oxygenation during laparoscopic cholecystectomy in obese patients. METHODS: One hundred and two adult patients of ASA physical status I and II, Body Mass Index of 30-40 kg/m(2), scheduled for laparoscopic cholecystectomy were included in this prospective randomized open-label parallel group study. To start with, all patients received VCV. Fifteen minutes after creation of pneumoperitoneum, they were randomized to receive either VCV (Group V) or PCV (Group P). The ventilatory parameters were adjusted accordingly to maintain the end-tidal CO(2) between 35 and 40 mmHg. Respiratory rate, tidal volume, minute ventilation and peak airway pressure were noted. Arterial blood gas analyses were done 15 min after creation of pneumoperitoneum and at 20-min intervals thereafter till the end of the surgery. All data were analysed statistically. RESULTS: Patients in Group P showed a statistically significant (P < 0.05) higher level of PaO(2) and lower value of PAO(2)-PaO(2) than those in Group V. CONCLUSION: PCV is a more effective mode of ventilation in comparison with VCV regarding oxygenation in obese patients undergoing laparoscopic cholecystectomy.