In vivo antimalarial activity of synthetic hepcidin against Plasmodium berghei in mice

Hormones in malaria infection: influence on disease severity, host physiology, and therapeutic opportunities

Human malaria, caused by Plasmodium parasites, is a fatal disease that disrupts the host's physiological balance and affects the neuroendocrine system. This review explores how malaria influences and is influenced by hormones. Malaria activates the Hypothalamus-Pituitary-Adrenal axis, leading to increased cortisol, aldosterone, and epinephrine. Cortisol, while reducing inflammation, aids parasite survival, whereas epinephrine helps manage hypoglycemia. The Hypothalamus-Pituitary-Gonad and Hypothalamus-Pituitary-Thyroid axes are also impacted, resulting in lower sex and thyroid hormone levels. Malaria disrupts the renin-angiotensin-aldosterone system (RAAS), causing higher angiotensin-II and aldosterone levels, contributing to edema, hyponatremia and hypertension. Malaria-induced anemia is exacerbated by increased hepcidin, which impairs iron absorption, reducing both iron availability for the parasite and red blood cell formation, despite elevated erythropoietin. Hypoglycemia is common due to decreased glucose production and hyperinsulinemia, although some cases show hyperglycemia due to stress hormones and inflammation. Hypocalcemia, and hypophosphatemia are associated with low Vitamin D3 and parathyroid hormone but high calcitonin. Hormones such as DHEA, melatonin, PTH, Vitamin D3, hepcidin, progesterone, and erythropoietin protects against malaria. Furthermore, synthetic analogs, receptor agonists and antagonists or mimics of hormones like DHEA, melatonin, serotonin, PTH, vitamin D3, estrogen, progesterone, angiotensin, and somatostatin are being explored as potential antimalarial treatments or adjunct therapies. Additionally, hormones like leptin and PCT are being studied as probable markers of malaria infection.

In Vitro and In Vivo Antimalarial Activity of LZ1, a Peptide Derived from Snake Cathelicidin

Antimalarial drug resistance is an enormous global threat. Recently, antimicrobial peptides (AMPs) are emerging as a new source of antimalarials. In this study, an AMP LZ1 derived from snake cathelicidin was identified with antimalarial activity. In the in vitro antiplasmodial assay, LZ1 showed strong suppression of blood stage Plasmodium falciparum (P. falciparum) with an IC50 value of 3.045 μM. In the in vivo antiplasmodial assay, LZ1 exerted a significant antimalarial activity against Plasmodium berghei (P. berghei) in a dose- and a time- dependent manner. In addition, LZ1 exhibited anti-inflammatory effects and attenuated liver-function impairment during P. berghei infection. Furthermore, by employing inhibitors against glycolysis and oxidative phosphorylation in erythrocytes, LZ1 specifically inhibited adenosine triphosphate (ATP) production in parasite-infected erythrocyte by selectively inhibiting the pyruvate kinase activity. In conclusion, the present study demonstrates that LZ1 is a potential candidate for novel antimalarials development.

Mudskipper (Boleophthalmus pectinirostris) Hepcidin-1 and Hepcidin-2 Present Different Gene Expression Profile and Antibacterial Activity and Possess Distinct Protective Effect against Edwardsiella tarda Infection

Hepcidins are small cysteine-rich antimicrobial peptides that play an important role in fish immunity against pathogens. Most fish species have two or more hepcidin homologs that have distinct functions. This study investigated the immune functions of mudskipper (Boleophthalmus pectinirostris) hepcidin-1 (BpHep-1) and hepcidin-2 (BpHep-2) in vitro and in vivo. Upon infection with Edwardsiella tarda, the expression of BpHep-1 and BpHep-2 mRNA in immune tissues was significantly upregulated, but the expression profiles were different. Chemically synthesized BpHep-1 and BpHep-2 mature peptides exhibited selective antibacterial activity against various bacterial species, and BpHep-2 exhibited a stronger antibacterial activity and broader spectrum than BpHep-1. BpHep-1 and BpHep-2 both inhibited the growth of E. tarda in vitro, with the latter being more effective than the former. In addition, both peptides induced hydrolysis of purified bacterial genomic DNA (gDNA) or gDNA in live bacteria. In vivo, an intraperitoneal injection of 1.0 μg/g BpHep-2 significantly improved the survival rate of mudskippers against E. tarda infection compared with 0.1 μg/g BpHep-2 or 0.1 and 1.0 μg/g BpHep-1. Similarly, only BpHep-2 treatment effectively reduced the tissue bacterial load in E. tarda-infected mudskippers. Furthermore, treatment with 1.0 or 10.0 μg/ml BpHep-2 promoted the phagocytic and bactericidal activities of mudskipper monocytes/macrophages (MO/MФ). However, only the highest dose (10.0 μg/ml) of BpHep-1 enhanced phagocytosis, and BpHep-1 exerted no obvious effects on bactericidal activity. In conclusion, BpHep-2 is a stronger bactericide than BpHep-1 in mudskippers, and acts not only by directly killing bacteria but also through an immunomodulatory function on MO/MФ.