Observations on the Extracellular Spaces and Intercellular Junctions inDiphyllobothrium dendriticum(Cestoda)

Anti-parasitic drugs modulate the non-selective channels formed by connexins or pannexins

The proteins connexins, innexins, and pannexins are the subunits of non-selective channels present in the cell membrane in vertebrates (connexins and pannexins) and invertebrates (innexins). These channels allow the transfer of ions and molecules across the cell membrane or, and in many cases, between the cytoplasm of neighboring cells. These channels participate in various physiological processes, particularly under pathophysiological conditions, such as bacterial, viral, and parasitic infections. Interestingly, some anti-parasitic drugs also block connexin- or pannexin-formed channels. Their effects on host channels permeable to molecules that favor parasitic infection can further explain the anti-parasitic effects of some of these compounds. In this review, the effects of drugs with known anti-parasitic activity that modulate non-selective channels formed by connexins or pannexins are discussed. Previous studies that have reported the presence of these proteins in worms, ectoparasites, and protozoa that cause parasitic infections have also been reviewed.

Role of gap junctions and hemichannels in parasitic infections

In vertebrates, connexins (Cxs) and pannexins (Panxs) are proteins that form gap junction channels and/or hemichannels located at cell-cell interfaces and cell surface, respectively. Similar channel types are formed by innexins in invertebrate cells. These channels serve as pathways for cellular communication that coordinate diverse physiologic processes. However, it is known that many acquired and inherited diseases deregulate Cx and/or Panx channels, condition that frequently worsens the pathological state of vertebrates. Recent evidences suggest that Cx and/or Panx hemichannels play a relevant role in bacterial and viral infections. Nonetheless, little is known about the role of Cx- and Panx-based channels in parasitic infections of vertebrates. In this review, available data on changes in Cx and gap junction channel changes induced by parasitic infections are summarized. Additionally, we describe recent findings that suggest possible roles of hemichannels in parasitic infections. Finally, the possibility of new therapeutic designs based on hemichannel blokers is presented.

Structure and diversity of cestode epithelia

Eucestodes have a simple aceolomate body structure and are conservative in terms of the numbers and nature of their cell types. Nevertheless, the cestodes form a diverse group with many strikingly different forms distinguished by the structure of their holdfasts, sexual tissues and embryos. These morphological adaptations have their origins in subtle variations in the structure of their cells and extracellular matrices. This review is concerned with the biology of eucestode epithelia and examines their structure and functions, interrelationships with other tissues, and gives insight into how their components are modified among the many taxa. Three features of cestode epithelia, namely, the occurrence of regional specialisation, microtriches and secretory components, are described. In addition, evidence is presented to suggest that some cestode epithelia are involved in developmental processes such as the nurture of embryos and maintenance of surrounding tissues.