Phagocytosis of hemozoin (native and synthetic malaria pigment), and Plasmodium falciparum intraerythrocyte-stage parasites by human and mouse phagocytes

Our plain-English summary of Phagocytosis of hemozoin (native and synthetic malaria pigment), and Plasmodium falciparum intraerythrocyte-stage parasites by human and mouse phagocytes, by P. Olliaro, L. Lombardi, S. Frigerio, et al (Ultrastructural Pathology, 2000).

The study

• Authors: P. Olliaro, L. Lombardi, S. Frigerio, N. Basilico, D. Taramelli, D. Monti
• Journal: Ultrastructural Pathology
• Published: 2000;24(1):9-13
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Hemozoin, the detoxification product of hemoglobin heme, piles up as electron-dense material in the food vacuole (FV) of intraerythrocytic malaria parasites (malaria pigment). In infected individuals, pigment is internalized by both circulating and resident phagocytes, thus modulating their functions. Synthetic beta-hematin, prepared in vitro from hematin (ferriprotoporphyrin IX hydroxide) in acidic condition, is spectroscopically identical to hemozoin. In this electron microscopy study, native and synthetic hemozoin also prove to be morphologically indistinguishable (large polygonal crystals with apparent transverse banding) and to undergo the same process when internalized by phagocytes (primarily a direct uptake of crystals, similar to what is described for asbestos fibers). On the contrary, whole parasites appear to follow a classical endocytic pathway. This suggests that there may be differences between the ingestion of free particles and whole parasites in terms of modulation of phagocytes' functions.

In plain English

This laboratory study used electron microscopy to look at malaria pigment (hemozoin), not asbestos. The authors compared hemozoin taken from Plasmodium falciparum parasite cultures with a synthetic version, beta-hematin, and examined how cells that engulf particles took them up. They used a mouse macrophage-like cell line (J774) and human monocytes from healthy blood donors. J774 cells were also given carbonyl iron particles, and monocytes were cultured with parasite-infected red blood cells. Native and synthetic pigment looked alike: polygonal crystals with apparent transverse banding. In J774 cells, within 25 minutes small crystal aggregates were mostly inside phagolysosomes. Larger clusters lay free in the cytoplasm with no membrane or a discontinuous one, and occasionally particles appeared to perforate the cell membrane. Parasite-derived pigment showed similar patterns. In monocytes that ingested infected red cells, crystals were inside vacuoles with a single membrane. The authors likened the free-particle uptake to what earlier studies describe for asbestos fibers, but this study did not test asbestos. They concluded that native and synthetic pigment are taken up the same way, and that ingesting free particles and whole parasites may differ.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) electron microscopy study of cultured cells
• Who was studied: Cells, not people: a murine macrophage-like cell line (J774) and human monocytes separated from the blood of healthy donors, plus laboratory-cultured P. falciparum parasites (NF54 strain) in human red blood cells
• Exposure: Synthetic beta-hematin, native hemozoin and carbonyl iron particles given to J774 macrophages (fixed at 25 min and 4 h), and P. falciparum-infected red blood cells given to human monocytes (fixed at 24 and 48 h). No asbestos was used.
• Main results:
  • Native hemozoin in the parasite food vacuole appeared as polygonal crystals forming larger banded structures, comparable to synthetic pigment
  • In J774 macrophages given synthetic pigment, larger crystal clusters were seen free in the cytoplasm with no membrane or a discontinuous membrane
  • Occasionally, synthetic pigment particles appeared to perforate the plasma membrane of J774 macrophages
  • Parasite-derived (native) pigment showed similar patterns of uptake in J774 macrophages
  • J774 macrophages fed carbonyl iron showed particles with a clear halo but no visible membrane
  • In human monocytes co-cultured with infected red blood cells, pigment crystals were inside vacuoles with a single membrane
• The authors' conclusion: The authors concluded that native and synthetic pigment are internalized by phagocytes in the same way, and that there may be differences between ingesting free particles and whole parasites. They compared the free-particle uptake to the uptake of asbestos fibers described in other studies.
• Limitations the authors state:
  • J774 cells could not be observed for longer incubation times because they grow quickly in culture

Topics

Medical terms in this study, explained in our Lexicon: Phagocytosis.

Related studies

• Immunopathological effects of malaria pigment or hemozoin and other crystals — A. Tyberghein, K. Deroost, et al. (2014)
• The role of Rho-kinases in IL-1β release through phagocytosis of fibrous particles in human monocytes — S. Kanno, S. Hirano, et al. (2015)
• Asbestos body phagocytosis by human free alveolar macrophages — T.L. McLemore, M.L. Mace, et al. (1980)
• Phagocytosis of asbestos fibers by human pulmonary alveolar macrophages — T. McLemore, M. Corson, et al. (1979)
• Comparison of phagocytosis of uncoated versus coated asbestos fibers by cultured human pulmonary alveolar macrophages — T.L. McLemore, V. Roggli, et al. (1981)
• Malarial pigment hemozoin and the innate inflammatory response — M. Olivier, K. Van Den Ham, et al. (2014)

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