Induction of autophagy through CLEC4E in combination with TLR4: an innovative strategy to restrict the survival of Mycobacterium tuberculosis

ABSTRACT

Host-directed therapies are gaining considerable impetus because of the emergence of drug-resistant strains of pathogens due to antibiotic therapy. Therefore, there is an urgent need to exploit alternative and novel strategies directed at host molecules to successfully restrict infections. The C-type lectin receptor CLEC4E and Toll-like receptor TLR4 expressed by host cells are among the first line of defense in encountering pathogens. Therefore, we exploited signaling of macrophages through CLEC4E in association with TLR4 agonists (C₄.T₄) to control the growth of Mycobacterium tuberculosis (Mtb). We observed significant improvement in host immunity and reduced bacterial load in the lungs of Mtb-infected mice and guinea pigs treated with C₄.T₄ agonists. Further, intracellular killing of Mtb was achieved with a 10-fold lower dose of isoniazid or rifampicin in conjunction with C₄.T₄ than the drugs alone. C₄.T₄ activated MYD88, PtdIns3K, STAT1 and RELA/NFKB, increased lysosome biogenesis, decreased Il10 and Il4 gene expression and enhanced macroautophagy/autophagy. Macrophages from autophagy-deficient (atg5 knockout or Becn1 knockdown) mice showed elevated survival of Mtb. The present findings also unveiled the novel role of CLEC4E in inducing autophagy through MYD88, which is required for control of Mtb growth. This study suggests a unique immunotherapeutic approach involving CLEC4E in conjunction with TLR4 to restrict the survival of Mtb through autophagy.     

Effects of dithizone on the electroencephalogram recorded from the mouse hippocampus in vivo

In the present study the author examined the effects of dithizone on hippocampal and cortical EEG by power spectral analysis in the moving mouse. Following results were obtained. Administration of dithizone 100 mg/kg i. p. produced almost loss of electrical activities on EEG which began 409 sec after injection and lasted approximately up to 706 sec. In recovery period waveform showed shift to slower frequencies apparent by 60 min. Heart rate decreases were seen between 5 and 20 min after 100 mg/kg i. p. injection. Dithizone produced dose-dependent changes in hippocampal and heart rate activities. Abolished EEG by dithizone administration were immediately recovered by zinc-acetate application. Injection of vehicle had no significant effect on hippocampal and cortical EEG.