Minocycline prevents cerebral malaria, confers neuroprotection and increases survivability of mice during Plasmodium berghei ANKA infection

Microglial Priming in Infections and Its Risk to Neurodegenerative Diseases

Infectious diseases of different etiologies have been associated with acute and long-term neurological consequences. The primary cause of these consequences appears to be an inflammatory process characterized primarily by a pro-inflammatory microglial state. Microglial cells, the local effectors’ cells of innate immunity, once faced by a stimulus, alter their morphology, and become a primary source of inflammatory cytokines that increase the inflammatory process of the brain. This inflammatory scenario exerts a critical role in the pathogenesis of neurodegenerative diseases. In recent years, several studies have shown the involvement of the microglial inflammatory response caused by infections in the development of neurodegenerative diseases. This has been associated with a transitory microglial state subsequent to an inflammatory response, known as microglial priming, in which these cells are more responsive to stimuli. Thus, systemic inflammation and infections induce a transitory state in microglia that may lead to changes in their state and function, making priming them for subsequent immune challenges. However, considering that microglia are long-lived cells and are repeatedly exposed to infections during a lifetime, microglial priming may not be beneficial. In this review, we discuss the relationship between infections and neurodegenerative diseases and how this may rely on microglial priming.

Systemic Response to Infection Induces Long-Term Cognitive Decline: Neuroinflammation and Oxidative Stress as Therapeutical Targets

In response to pathogens or damage signs, the immune system is activated in order to eliminate the noxious stimuli. The inflammatory response to infectious diseases induces systemic events, including cytokine storm phenomenon, vascular dysfunction, and coagulopathy, that can lead to multiple-organ dysfunction. The central nervous system (CNS) is one of the major organs affected, and symptoms such as sickness behavior (depression and fever, among others), or even delirium, can be observed due to activation of endothelial and glial cells, leading to neuroinflammation. Several reports have been shown that, due to CNS alterations caused by neuroinflammation, some sequels can be developed in special cognitive decline. There is still no any treatment to avoid cognitive impairment, especially those developed due to systemic infectious diseases, but preclinical and clinical trials have pointed out controlling neuroinflammatory events to avoid the development of this sequel. In this minireview, we point to the possible mechanisms that triggers long-term cognitive decline, proposing the acute neuroinflammatory events as a potential therapeutical target to treat this sequel that has been associated to several infectious diseases, such as malaria, sepsis, and, more recently, the new SARS-Cov2 infection.

Network-Based Approaches Reveal Potential Therapeutic Targets for Host-Directed Antileishmanial Therapy Driving Drug Repurposing

Leishmania parasites are the causal agent of leishmaniasis, an endemic disease in more than 90 countries worldwide. Over the years, traditional approaches focused on the parasite when developing treatments against leishmaniasis. Despite numerous attempts, there is not yet a universal treatment, and those available have allowed for the appearance of resistance. Here, we propose and follow a host-directed approach that aims to overcome the current lack of treatment. Our approach identifies potential therapeutic targets in the host cell and proposes known drug interactions aiming to improve the immune response and to block the host machinery necessary for the survival of the parasite. We started analyzing transcription factor regulatory networks of macrophages infected with Leishmania major. Next, based on the regulatory dynamics of the infection and available gene expression profiles, we selected potential therapeutic target proteins. The function of these proteins was then analyzed following a multilayered network scheme in which we combined information on metabolic pathways with known drugs that have a direct connection with the activity carried out by these proteins. Using our approach, we were able to identify five host protein-coding gene products that are potential therapeutic targets for treating leishmaniasis. Moreover, from the 11 drugs known to interact with the function performed by these proteins, 3 have already been tested against this parasite, verifying in this way our novel methodology. More importantly, the remaining eight drugs previously employed to treat other diseases, remain as promising yet-untested antileishmanial therapies. IMPORTANCE This work opens a new path to fight parasites by targeting host molecular functions by repurposing available and approved drugs. We created a novel approach to identify key proteins involved in any biological process by combining gene regulatory networks and expression profiles. Once proteins have been selected, our approach employs a multilayered network methodology that relates proteins to functions to drugs that alter these functions. By applying our novel approach to macrophages during the Leishmania infection process, we both validated our work and found eight drugs already approved for use in humans that to the best of our knowledge were never employed to treat leishmaniasis, rendering our work as a new tool in the box available to the scientific community fighting parasites.

Treatment and protective effects of metalloproteinase inhibitors alone and in combination with N-Acetyl cysteine plus vitamin E in rats exposed to aflatoxin B1

This study was conducted to investigate the effects of matrix metalloproteinase (MMP) inhibitors dexamethasone and minocycline administrations -both single and in combination with N-acetylcysteine (NAC) and vitamin E-on the tissue distribution and lethal dose (LD)₅₀ of aflatoxin (AF)B₁ in rats. We performed this study on male Wistar rats (8-10 weeks) in two phases. In the first phase, rats were administered dexamethasone (5 and 20 mg/kg) and minocycline (45 and 90 mg/kg), both as single treatments and in combination with NAC (200 mg/kg) and vitamin E (600 mg/kg); these treatments followed AFB₁ administration (2 mg/kg). In the second phase, the therapeutic effect value (TEV) was calculated to determine the treatment effect on the LD₅₀ level of AFB₁. The tissue affinity of AFB1 from high to low was liver, kidney, intestine, brain, heart, spleen, lung, testis, and vitreous humor, respectively. Dexamethasone at the 20 mg/kg dose significantly reduced AFB₁ concentrations in the plasma and the other tissues, except for the vitreous humor. The effects of minocycline on the plasma and tissue concentrations of AFB₁ varied by dose and tissue. The combinations of dexamethasone or minocycline with NAC and vitamin E increased the AFB₁ concentrations in the plasma and all tissues, except for vitreous humor and liver. In male rats, the LD₅₀ value of AFB₁ was 11.86 mg/kg. The TEV of dexamethasone (20 mg/kg) was calculated to be 1.5. Dexamethasone can be administered in repeated doses at ≥20 mg/kg to increase survival in AFB₁ poisoning.

Repurposing Drugs to Fight Hepatic Malaria Parasites

Malaria remains one of the most prevalent infectious diseases worldwide, primarily affecting some of the most vulnerable populations around the globe. Despite achievements in the treatment of this devastating disease, there is still an urgent need for the discovery of new drugs that tackle infection by Plasmodium parasites. However, de novo drug development is a costly and time-consuming process. An alternative strategy is to evaluate the anti-plasmodial activity of compounds that are already approved for other purposes, an approach known as drug repurposing. Here, we will review efforts to assess the anti-plasmodial activity of existing drugs, with an emphasis on the obligatory and clinically silent liver stage of infection. We will also review the current knowledge on the classes of compounds that might be therapeutically relevant against Plasmodium in the context of other communicable diseases that are prevalent in regions where malaria is endemic. Repositioning existing compounds may constitute a faster solution to the current gap of prophylactic and therapeutic drugs that act on Plasmodium parasites, overall contributing to the global effort of malaria eradication.

Neurological disorder and psychosocial aspects of cerebral malaria: what is new on its pathogenesis and complications? A minireview

Recently, malaria is remain considered as the most prevalent infectious disease, affecting the human health globally. High morbidity and mortality worldwide is often allied with cerebral malaria (CM) based disorders of the central nervous system, especially across many tropical and sub-tropical regions. These disorders are characterised by the infection of Plasmodium species, which leads to acute or chronic neurological disorders, even after having active/effective antimalarial drugs. Furthermore, even during the treatment, individual remain sensitive for neurological impairments in the form of decrease blood flow and vascular obstruction in brain including many more other changes. This review briefly explains and update on the epidemiology, burden of disease, pathogenesis and role of CM in neurological disorders with behaviour and function in mouse and human models. Moreover, the social stigma, which plays an important role in neurological disorders and a factor for assessing CM, is also discussed in this review.

The allosteric modulation effects of doxycycline, minocycline, and their derivatives on the neuropeptide receptor PAC1-R

Class B G-protein coupled receptors (GPCR) PAC1-R is a neuropeptide pituitary adenylate cyclase activating polypeptide (PACAP)-preferring receptor that mediates the effective neuroprotective activity. Based on our previous data showing that doxycycline and minocycline work as the positive allosteric modulator (PAM) of PAC1-R, we used computer molecular docking and isothermal titration calorimetry assay to further determine the bindings of doxycycline/minocycline's derivatives including tetracycline/tigecycline with the N-terminal extracellular domain of PAC1-R (PAC1-EC1). Then the cAMP assay combined with the PAC1-R natural agonist PACAP27 was used to confirm the possible PAM roles of the small-molecule antibiotics. The results showed that tetracycline/tigecycline had significant lower affinity to PAC1-EC1 than doxycycline/minocycline, which was consistent with their non-positive allosteric modulation activity on PAC1-R. Furthermore, by comparing the key residues contributing to the PAM binding with the predicted allosteric site in PAC1-EC1, we characterized four motifs contributing to PAM binding in PAC1-EC1. The site-directed mutation results showed that ASN60 played the most important role in the PAM binding of the small-molecule antibiotics, while ASP116 played a sensitive marginal role in the PAM binding. These results not only help to explain the clinical and experimental neuroprotective effects of doxycycline/minocycline, but also help to characterize the PAM binding site in PAC1-EC1, which will promote the screening and characterization of novel small-molecule PAMs targeting PAC1-EC1 with drug development potency in nerve system disease.

Blood-Brain Barrier in Cerebral Malaria: Pathogenesis and Therapeutic Intervention

Cerebral malaria is a life-threatening complication of malaria caused by the parasite Plasmodium falciparum. The growing problem of drug resistance and the dearth of new antiparasitic drugs are a serious threat to the antimalaria treatment regimes. Studies on humans and the murine model have implicated the disruption of the blood-brain barrier (BBB) in the lethal course of the disease. Therefore, efforts to alleviate the BBB dysfunction could serve as an adjunct therapy. Here, we review the mechanisms associated with the disruption of the BBB. In addition, we discuss the current, still limited, knowledge on the contribution of different cell types, microparticles, and the kynurenine pathway in the regulation of BBB dysfunction, and how these molecules could be used as potential new therapeutic targets.

Inhibiting the NLRP3 Inflammasome With Methylene Blue as Treatment Adjunct in Myelodysplasia

Myelodysplasia refers to a group of clonal hematopoietic neoplasms characterized by genetic heterogeneity, different clinical behaviors and prognoses. Some of this group of bone marrow failure conditions have known external causes, some are of unknown origin. Within marrow, intracellular, and extracellular elements of the innate immune system are activated and contribute to creation of multiple cytogenetic abnormalities and are central to the mode of hematopoietic cell failure. Basiorka et al. showed that NLRP3 inflammasome activity is essential to the innate immune system's destruction of marrow hematopoietic cells commonly in myelodysplasia. In April 2018 Hao et al. reported that methylene blue inhibits rat NLRP3 inflammasome function. Methylene blue has been in continuous use in humans for over a century. It is associated with an eminently benign side effect profile in human use. If as in rodents, methylene blue also inhibits NLRP3 inflammasome function in human myelodysplasia a trial of adjunctive methylene blue treatment in transfusion dependent, low risk myelodysplasia where marrow inflammation and apoptosis predominates, would be worth trying.

HIGHLIGHTS

- Cytogenetic abnormalities and innate immune activation are seen in myelodysplasia

- The NLRP3 inflammasome is a core element generating marrow failure of myelodysplasia

- In April 2018 methylene blue was reported to potently inhibit NLRP3 inflammasome function

- Methylene blue has benign side effects and has been in human use for a century

- Study of methylene blue treatment of myelodysplasia would be a low-risk intervention

Susceptibility of mice strains to oxidative stress and neurotransmitter activity induced by Plasmodium berghei

This study investigated the susceptibility of female C57Bl/6 and Swiss Albino mice to oxidative stress and neurotransmitters activity induced by Plasmodium berghei. On day 9 p.i. with P. berghei infected erythrocytes, the mice reduced in weight. This weight loss was markedly higher in SW mice and reached about −14%. Also, the infection was able to cause oxidative damage to the brain tissue. Catalase activity as well as glutathione, malondialdehyde and nitric oxide levels were different in the two mice strains. Moreover, the brain content of neurotransmitters, epinephrine, norepinephrine, dopamine and serotonin in mice brain was higher in SW mice than B6 mice. We concluded that, the strain of mice is one factor that could alter the response of mice to P. berghei infection.