This medical pathophysiology diagram illustrates the three-stage molecular mechanism of action of artemisinins against the Plasmodium parasite. (Part A) Primary carbon-centered radical formation: Hemoglobin is digested by plasmepsins and falcipain 2 into heme (protoporphyrin IX and Fe2+). Heme iron triggers the reductive activation of the artemisinin endoperoxide bridge via homolytic O-O bond cleavage or C3-C4 cleavage, forming a highly reactive primary carbon-centered radical. (Part B) Heme alkylation: The resulting alkylating radical reacts with the heme molecule to form a heme-artemisinin adduct. This chemical modification causes steric hindrance, preventing the parasite from detoxifying heme into nontoxic hemozoin crystals. (Part C) ROS generation: The inhibited heme-artemisinin complex facilitates electron transfer involving glutathione, NADPH, and reductases. This triggers a redox cascade: molecular oxygen (O2) is reduced to superoxide radicals (O2•−), which superoxide dismutase (SOD) converts to hydrogen peroxide (H2O2). Finally, Fenton-like chemistry generates the highly deleterious hydroxyl radical (•OH). The cycling of iron between Fe2+ and Fe3+ states drives this oxidative stress, ultimately leading to parasite cellular damage and death.

This pathophysiology diagram illustrates the dual pathways of Primary Brain Injury (PBI) and Secondary Brain Injury (SBI) following an Intracerebral Hemorrhage (ICH) within the human brain. The PBI pathway (left) focuses on mechanical complications: Hematoma formation leads to perihematomal edema and hematoma expansion, creating a mass effect. This causes increased Intracranial Pressure (ICP), leading to brain hernia and potentially death. The central region highlights shared pathological hallmarks, including blood-brain barrier (BBB) breakdown, edema, inflammation, neuronal injury, and oxidative stress. The SBI pathway (right) details biochemical cascades: blood leakage results in thrombin-mediated leukocyte infiltration and erythrocyte lysis. The lysis releases hemoglobin (activating TLR2/TLR4) and heme, which is processed by HO-1 and HO-2 into iron. Iron-driven Fenton reactions and hemoglobin activation contribute to a central node of reactive oxygen species (ROS) and inflammation. This cascade ultimately triggers cellular death mechanisms, including apoptosis, autophagy, and pyroptosis. The diagram serves as an educational summary of the complex interplay between mechanical pressure and neuroinflammatory cascades in hemorrhagic stroke.

This pathophysiology diagram illustrates the regulation and role of Heme Oxygenase-1 (HO-1) in various renal and systemic pathologies. The schematic categorizes diseases into two groups: 'Diseases associated with massive heme release' (red box) and 'Diseases not associated with massive heme release' (blue box). The first group includes intravascular hemolysis (SCA, HUS, malaria, PNH) and rhabdomyolysis, visually linked to red blood cell lysis (hemoglobin) and muscle fiber injury (myoglobin), respectively, resulting in significant 'Free heme' levels. The second group comprises conditions like glomerulopathies, ischemia-reperfusion, sepsis AKI, and hypertension, which involve cytochromes and have a suspected link (dotted arrow) to free heme. Centrally, HO-1 is shown degrading free heme into iron, carbon monoxide (CO), and biliverdin. The diagram details molecular regulation of HO-1, highlighting induction by transcription factors such as Nrf2, HIF, and AP-1. Inhibitory mechanisms are also depicted, specifically the inhibition of Nrf2 by KEAP1 and the direct inhibition of HO-1 expression by Bach1. This visual summary provides a clinical context for the cytoprotective role of the HO-1 pathway in nephrology.

This pathophysiology diagram illustrates the metabolic processes within a Plasmodium-infected erythrocyte leading to oxidative stress. On the left, a red blood cell is shown infected with Plasmodium parasites. An enlarged view of the parasite's cytosol and digestive vacuole details the breakdown of host hemoglobin by proteases (Plasmepsin, Falcipain, Falcilysin) into amino acids for parasite nutrition and free Heme-Fe2+. While some heme is sequestered as non-toxic hemozoin, a portion undergoes oxidation. The diagram maps the biochemical pathway where Heme-Fe2+ reacts with O2 to produce superoxide (O2•−) and Fe3+. Superoxide is converted to hydrogen peroxide (H2O2) via superoxide dismutase (SOD), which then participates in the Fenton and Haber-Weiss reactions to generate hydroxyl radicals (OH•). Simultaneously, superoxide reacts with nitric oxide (NO) to form peroxynitrite (OONO−). Both OH• and OONO− are shown converging on a central 'Oxidative Stress' node, highlighting the generation of reactive oxygen and nitrogen species (RONS) as a consequence of intraerythrocytic malarial metabolism.

This medical pathophysiology diagram illustrates the heme biosynthesis pathway and its associated acute hepatic porphyrias. The flow is depicted across two cellular compartments: the mitochondria and the cytoplasm. The pathway begins in the mitochondria where Succinyl-CoA and Glycine are converted by ALAS (delta-aminolevulinic acid synthase) into delta-aminolevulinic acid (ALA). The process then moves to the cytoplasm, proceeding through intermediates: porphobilinogen (PBG), hydroxymethylbilane, uroporphyrinogen III, and coproporphyrinogen III, facilitated by enzymes ALAD, HMBS, UROS, and UROD respectively. The final stages return to the mitochondria, where coproporphyrinogen III is converted to protoporphyrinogen and then protoporphyrin IX via CPOX and PPOX. In the final step, ferrochelatase (FECH) incorporates iron (Fe) into protoporphyrin IX to form heme. The diagram explicitly links specific enzyme deficiencies to clinical conditions: ALAD deficiency porphyria (ADP), acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), and variegate porphyria (VP). The visual uses chemical structures, enzyme labels, and mitochondrial representation to detail the metabolic sequence.

This composite educational infographic illustrates the pathophysiology of Porphyria Cutanea Tarda (PCT) through three integrated sections. Section A depicts the normal heme biosynthesis pathway in the liver, showing the enzymatic conversion starting from Glycine and Succinyl CoA, through intermediates like ALA, PBG, HMB, and Uroporphyrinogen III, catalyzed by enzymes including ALAS, ALAD, and UROD, culminating in HEME production. Section B focuses on the molecular pathogenesis of PCT, highlighting the inhibition of the enzyme Uroporphyrinogen Decarboxylase (UROD). This block leads to the accumulation of porphyrins, which is visually linked to a large chemical structure diagram. Section C demonstrates the clinical manifestation of this metabolic defect. It shows a human arm with a magnified view of cutaneous bullae (blisters) and a sun icon, illustrating how light-activated porphyrins cause mast cell degranulation and oxidative damage to skin layers. The diagram serves as an educational tool for understanding the link between hepatic enzymatic deficiencies and dermatological photosensitivity.

This intraoperative clinical photograph demonstrates 5-aminolevulinic acid (ALA)-guided photodynamic diagnosis (PDD) during cytoreductive surgery for peritoneal malignancy. The image shows a dark reddish surgical site, likely the peritoneal surface, containing multiple small, whitish, translucent residual nodules. Under violet light excitation (405 nm), one specific nodule exhibits prominent red fluorescence, indicative of tumor-specific protoporphyrin IX (PpIX) accumulation. A surgical grasping instrument held by a green-gloved hand is seen precisely targeting this fluorescing nodule for excision. This visual illustrates the clinical utility of PDD in identifying microscopic or residual disease that may be missed under standard white light after macroscopic complete resection. The technique leverages the heme synthesis pathway where cancer cells selectively accumulate PpIX, facilitating more thorough cytoreduction in surgical oncology.